HUDSON RIVER SHORELINE RESTORATION ALTERNATIVES ANALYSIS

5/20/2018 HUDSON RIVER SHORELINE RESTORATION ALTERNATIVES ANALYSIS

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HUDSON RIVER SHORELINE RESTORATIONALTERNATIVES ANALYSIS

March 2006

Prepared for:

Hudson River National Estuarine Research Reserve

Hudson River Estuary Program

New England Interstate Water Pollution Control Commission

Prepared by:

Alden Research Laboratory, Inc.

Gregory Allen, Civil EngineerThomas Cook, P.E., Director of Environmental Services

Edward Taft, President

ASA Analysis & Communications, Inc.John Young, Ph.D., Senior Scientist

David Mosier, Scientist

ALDENSolving Flow Problems Since 1894


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HUDSON RIVER SHORELINE RESTORATION ALTERNATIVES ANALYSIS

This report was prepared by ASA Analysis and Communications, Inc. and Alden ResearchLaboratory, Inc. under award NA03NOS4200141 from the National Oceanic and AtmosphericAdministration, U.S. Department of Commerce. The statements, findings, conclusions, andrecommendations are those of the authors and do not necessarily reflect the views of the NationalOceanic and Atmospheric Administration or the Department of Commerce.


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EXECUTIVE SUMMARY

The Hudson River Estuary shoreline,extending from the rivers mouth in NewYork City to the Troy Dam, is very differenttoday from the shoreline that existed whenHenry Hudson first sailed up the river in1609. The shoreline has undergone constantnatural erosional and depositional processes,and has been subject to human modificationon a significant scale since the time ofEuropean settlement of the valley.Modifications have included dredging anavigation channel, disposal of dredgedmaterial which created new islands andconnected and expanded existing islands,creation of railroad beds on both sides of theriver, installation of hardened shorelinestructures, marinas, docking facilities, andother development. The cumulative resultof these activities has adversely affectedboth the quality and quantity of the riparianand near shore aquatic habitat. The naturalecological communities that existed prior tothese activities have been transformed to

cultural (modified) communities that maynot perform the same ecological functions ashabitat for fish and wildlife. In addition,these modified areas may not provide otheramenities, such as aesthetic enjoyment, oropportunities to fish, swim, or otherwise usethe estuary.

The Hudson River National EstuarineResearch Reserve (Reserve) and the HudsonRiver Estuary Program (both part of the

New York State, Department ofEnvironmental Conservation [NYSDEC]),in conjunction with the New EnglandInterstate Water Pollution ControlCommission, contracted ASA Analysis &Communication (ASA) and Alden ResearchLaboratory, Inc. (Alden) to investigateoptions for restoring both ecological and

sociological functions by enhancingshoreline habitats through soft engineering

technologies. The project was completed byconducting the following tasks:

A review of available literature onshoreline stabilization methods

Field survey of potential shorelinerestoration sites in the Hudson RiverEstuary

Evaluation of preliminary designs forfive example shoreline restoration sites

Description of the regulatory process forconducting the restoration projects

This report presents the literature review, asynthesis of the field survey, an evaluationof five potential shoreline restoration sites,and a summary of the regulatory process.

Literature Review

River bank stabilization techniques found inliterature that have potential to improveaquatic habitat for fish were reviewed.

Initially, information on all availabletechniques was reviewed. It was found thatthe majority of the information applies torestoration of small fresh water rivers andstreams. However, some of the techniqueswere deemed to be potentially appropriatefor the tidal Hudson River Estuary.

The literature search was performedelectronically. Reference databases thatwere queried included:

Ingenta

EBSCOHost

Scientific Research

Illumina

Engineering Village

USACE


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ASCE

NRCS

University reference libraries (University ofMassachusetts and Pennsylvania State

University) were accessed to obtainreferences that could not be obtaineddirectly off the internet.

Much of the information on techniquesapplicable to the Hudson River came from anumber of comprehensive review documents(FISRWG 1998, USDA NRCS 1996,GSWCC 2000, Allen and Leech 1997, Grayand Sotir 1996, Schiechtl 1980, Schiechtland Stern 1997, Landphair and Li 2002).

Stabilization methods were consideredappropriate for Hudson River application ifthey could withstand a shear stress greaterthan 2.5 lbs/ft2. This shear stress waschosen because it is equivalent to thelimiting shear stress for six inch riprap,which was considered to be the minimumrequired for the majority of shoreline alongthe Hudson River Estuary. The followingfive restoration techniques were identifiedfrom the literature review as being

appropriate:

Vegetated Geogrids Brush layeringwith each soil layer wrapped in ageosynthetic material

Live Crib Wall Box like arrangementof interlocking logs, timbers, pre-castconcrete or plastic structural members.The crib is filled with layers of soil andlive cuttings.

Brush mattresses Live cuttings with

branches on the slope with butt endskeyed into toe protection. The branchesare layered in a criss-cross overlappingpattern and secured with wire and deadstout stakes. A rock toe or fascine isused for toe protection.

Joint Planting Riprap slope with live

stakes driven into the joints between therocks.

Vegetated Rock Gabion Walls orMattresses Gabion baskets made ofwelded or twisted wire tied together andfilled with rocks. The baskets arestacked like bricks (gabion wall) with alayer of soil and live cuttings betweeneach course of baskets. Alternatively,the baskets could be laid out on a slopelike tiles (gabion mattress) with soil andlive cuttings between baskets.

Surveys and Site Selection

River surveys of the estuary shoreline wereconducted to qualitatively assess the currenttypes, and condition of natural andengineered shoreline habitats betweenPiermont Marsh and Troy Dam.Information obtained from the river surveyswas used to choose five shoreline sites todevelop preliminary designs as examples ofsoft shoreline restoration using thetechniques identified in the literature review.

An initial survey of the Hudson River

Estuary conducted in August 2005 provideda visual survey of the entire Hudson RiverEstuary shoreline targeted for the restorationanalysis. Information gathered from thissurvey was used to prepare a list ofcandidate example sites to be considered fora detailed evaluation of alternative shorelineprotection measures.

A total of 11 potential sites were identifieddistributed throughout the Hudson RiverEstuary. These sites were provided to the

project team for consideration. The siteswere assessed based on the followingcriteria:

Shoreline type

Current condition

Opportunity for improvement


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Regional distribution of all proposed

sites Landscape context (urban/rural)

Project applicability to other sites in theHudson River Estuary

Site specific consideration

The team selected five out of the eleven sitesfor development of preliminary softengineering designs as examples that couldbe used throughout the estuary. These siteswere chosen due to perceived advantagesover the other six candidate sites:

1. Bowline Point Park, Haverstraw

2. Newburgh

3.

Poughkeepsie4. Henry Hudson Park, Bethlehem

5. Campbell Island, Castleton on theHudson

The five sites were further evaluated andpreliminary designs were developed. Thesoft engineering techniques identified fromthe literature review were considered at eachexample site. The evaluation of eachshoreline site included:

hydraulic conditions,

erosion and sediment conditions,

construction considerations,

estimated costs,

project operation and maintenance

requirements,

expected benefits

Each technique identified was qualitatively

screened for potential application at the fiveselected shoreline restoration example sites.The joint planting stabilization techniquewas considered to be the most appropriatefor application most of the sites. Thisalternative was the most flexible toincorporate into retrofit designs. Most siteshave portions of existing rock slopes or

slopes that could be simply modified toaccommodate live stake installations. Otheralternatives required extensive excavation,grubbing, and redesign of the entireshorelines.

The shoreline restoration modificationsranged from $75/ft at Bowline Park to$983/ft at Campbell Island. The mainfactors that affected the installation costswere shoreline access and the amount theslope had to be cut back (excavation). AtBowline Point Park, the shoreline isaccessible from shore and would not requireextensive slope re-grading. By contrast,Campbell Island would require a significantslope cut and is only accessible using bargemounted equipment.

Unit costs for joint planting ranged from$3.75/ft

2at Bowline Point Park to $36.63/ft

2

at Campbell Island. The available literaturelisted joint planting costs ranging from $1/ft2to $5/ft

2, not including riprap or site

excavation. These costs compare well withour developed costs if you consider theextent of riprap and excavation required foreach site. The available literature listed

vegetative geogrid costs ranging from$16/ft

2to $37/ft

2. The literature reported

cost is about 50% less than the developedcosts for vegetative geogrids at CampbellIsland ($65.50/ft2). The higher cost atCampbell Island is likely due to bargemounted equipment and excessiveexcavation.

Recommendations

Baseline data should be gathered before

implementation of a restoration project todetermine the net benefits of the shore linetreatment. After the project is implementedfollow-up monitoring should be conductedand the data compared for several years.The following information should begathered before and monitored afterimplementation of a project:


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Bank stability

Assessment of riparian plantings

Emergent vegetation assessment

Assessment of refuge/spawning habitatsand overall fish use.

Assessment of riparian wildlife habitat


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ACKNOWLEDGEMENTS

Alden and ASA would like to thank staff of the New York State Department of EnvironmentalConservation, Hudson River National Estuarine Research Reserve, Hudson River EstuaryProgram and the New England Interstate Water Pollution Control Commission for input, andassistance for this project. We would also like to thank the New York State Department of Statestaff for providing useful comments and advice. Specific personnel acknowledgements include:

Daniel Miller, Habitat Restoration Coordinator, Hudson River Estuary Program. Dan was theProject Manager and provided input and guidance to all aspects of the project including athorough tour of the entire Hudson River Estuary.

Geofrey Eckerlin, Environmental Analyst, Hudson River National Estuarine Research Reserve.Geof provided valuable assistance conducting the river surveys and piloting the boat.

Emilie Hauser, Coastal Training Program Coordinator, Hudson River National EstuarineResearch Reserve. Emilie provided input and guidance in developing this report andimplementing a training program.

Daniel Giza, Biologist, Alden Research Laboratory. Dan was an integral part of the shorelineriver surveys.


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Table of Contents

Section 1 Introduction................................................................................................................... 1

Section 2 Hudson River Estuary Shoreline..................................................................................... 2

Morphometry .............................................................................................................................. 2

Erosional Forces.......................................................................................................................... 2

Ecological Communities............................................................................................................. 5

Habitats & Communities............................................................................................................. 6

Habitat Modifications ................................................................................................................. 8

Shoreline Hardening ................................................................................................................... 8

Section 3 A Synthesis of Literature on Shoreline Stabilization Methods and HabitatEnhancements Applicable to the Hudson River Estuary................................................................ 9

Review of Available Literature Applicable to the Hudson River............................................... 9

Alternative Shoreline Stabilization Methods............................................................................ 15

Applicability (of) Existing Shorelines ...................................................................................... 27

Vegetation for Stabilization Methods ....................................................................................... 27

Costs.......................................................................................................................................... 28

Section 4 Estuary Shoreline River Surveys and Selection of Shoreline Restoration Sites for CaseStudies of Soft Engineering Design .......................................................................................... 31

Initial Shoreline River Survey .................................................................................................. 31

Selection of Restoration Sites for Preliminary Soft Engineering Designs............................ 31

Section 5 Preliminary Soft Engineering Designs and Detailed Evaluation of Selected ShorelineExample Sites................................................................................................................................ 39

Detailed Shoreline Survey of Selected Sites............................................................................. 39

Bowline Point Park ................................................................................................................... 41

Newburgh.................................................................................................................................. 53

Poughkeepsie ............................................................................................................................ 61

Henry Hudson Park................................................................................................................... 72

Campbell Island ........................................................................................................................ 81

Section 6 Regulatory Requirements.............................................................................................. 92

Section 7 Summary and Recommendations ................................................................................. 97

Summary................................................................................................................................... 97

Recommendations................................................................................................................... 100

Section 8 References................................................................................................................... 101


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Appendix A, Glossary

Appendix B, Plants for Soil Bioengineering and Associated Systems for the Northeast Region

Appendix C, Cost Estimates

Appendix D, Vendors for bioengineering products


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List of Tables

Table 1 Hudson River Morphometry............................................................................................. 3

Table 2 Available River Bank Stabilization Techniques1............................................................ 11

Table 3 Permissible Shear Stress and Velocity for Selected Lining Materials (Fischenich 2001)............................................................................................................................................... 14

Table 4 Stress and Velocity Levels for Vegetated Geogrid (Sotir and Fischenich 2003) ........... 16

Table 5 Stress and Velocity Levels for the Brush mattress (Allen and Fischenich 2000)........... 22

Table 6 Allowable Velocities for Rock Gabions (Chaychuk 2005) ............................................ 25

Table 7 Approximate Costs of Riverbank Stabilization Technique1........................................... 29

Table 8 Vegetative and Bioengineering Labor Estimates (Allen and Fischenich 2000) ............. 30

Table 9 NYSDEC Division of Environmental Permits Regional Offices ................................... 94

Table 10 Local governmental agencies that have reached the local adoption stage of a LocalWaterfront Revitalization Plan as of February 1, 2006 (Source: NYS Department of Statehttp://www.nyswaterfronts.com/downloads/pdfs/LWRP_Status_Sheet.pdf)....................... 96

Table 11 Evaluation Summary..................................................................................................... 98


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List of Figures

Figure 1 Tidal Zones...................................................................................................................... 4

Figure 2 Vegetated Geogrid (USDA NRCS 1996)...................................................................... 16

Figure 3 Live Crib Wall (USDA NRCS 1996)............................................................................ 18

Figure 4 Existing Shoreline (similar to Joint Planting design) .................................................... 19

Figure 5 Joint Planting (USDA NRCS 1996) .............................................................................. 20

Figure 6 Vegetative Cellular Concrete Block (USDA NRCS 1996) ........................................... 20

Figure 7 Brush Mattress (USDA NRCS 1996)............................................................................ 23

Figure 8 Vegetative Rock Gabion Wall (USDA NRCS 1996).................................................... 26

Figure 9 Vegetative Rock Gabion Mattress (Allen and Leech 1997).......................................... 26

Figure 10 Hudson River Selected Shoreline Stabilization Sites.................................................. 40

Figure 11 Bowline Park General Vicinity ................................................................................... 46Figure 12 Bowline Park, Existing Conditions Plan ..................................................................... 47

Figure 13 Bowline Park, Existing Conditions Section A ............................................................ 48

Figure 14 Bowline Park, Existing Conditions Section B............................................................. 49

Figure 15 Bowline Point Park Preliminary Soft Engineering Design Cross Section .................. 50

Figure 16 Bowline Park Preliminary Soft Engineering Design Cross Section A........................ 51

Figure 17 Bowline Park Preliminary Soft Engineering Design Cross Section B........................ 52

Figure 18 Newburgh, General Vicinity ....................................................................................... 56

Figure 19 Newburgh, Existing Conditions Plan .......................................................................... 57

Figure 20 Newburgh, Existing Conditions Section A ................................................................. 58

Figure 21 Newburgh, Existing Conditions Section B.................................................................. 59

Figure 22 Newburgh Preliminary Soft Engineering Design Cross Section................................. 60

Figure 23 Poughkeepsie General Vicinity ................................................................................... 65

Figure 24 Poughkeepsie Existing Conditions Plan...................................................................... 66

Figure 25 Poughkeepsie Existing Conditions Section A ............................................................. 67

Figure 26 Poughkeepsie Existing Conditions Section B ............................................................. 68

Figure 27 Poughkeepsie Existing Conditions Section C ............................................................. 69

Figure 28 Poughkeepsie Preliminary Soft Engineering Design Section A.................................. 70

Figure 29 Poughkeepsie Preliminary Soft Engineering Design Cross Section B........................ 71

Figure 30 Henry Hudson Park General Vicinity.......................................................................... 76

Figure 31 Henry Hudson Park, Existing Conditions Plan ........................................................... 77


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Figure 32 Henry Hudson Park, Existing Conditions Section A................................................... 78

Figure 33 Henry Hudson Park, Existing Conditions Section B................................................... 79

Figure 34 Henry Hudson Park Preliminary Soft Engineering Design Cross Section A.............. 80

Figure 35 Campbell Island General Vicinity............................................................................... 86

Figure 36 Campbell Island, Existing Conditions Plan................................................................. 87

Figure 37 Campbell Island, Existing Conditions Section............................................................ 88

Figure 38 Campbell Island Preliminary Soft Engineering Design Cross Section ....................... 89



Figure 41 Uniform Procedures Act (UPA) Permit Process ......................................................... 95


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Section 1 Introduction

The shoreline of the Hudson River Estuary,which extends from the rivers mouth inNew York City to the Troy Dam, is very

different today from the shoreline thatexisted in 1609 when Henry Hudson firstsailed up the river. The Hudsons shoreline,like all river shorelines is subject toconstant, although usually gradual, naturalchanges due to the processes of erosion anddeposition. Erosion of soil, sand and rockwithin the watershed and along shorelinesdue to surface runoff, wave action, highflow velocities, and ice scouring, eventuallybecomes deposition in areas of lower water

velocity along shorelines, in subtidal areas,or at the mouth of the estuary. Althoughtidal rivers such as the Hudson Estuary aresomewhat buffered against extreme highflow, unusual events such as severe stormscoincident with peak tidal phases cantemporarily reverse erosional anddepositional patterns, resulting in rapid andsubstantial changes to the shoreline.

These natural morphometric processes canbe accelerated or decelerated by humanactivity in the watershed and along theshoreline. Some activities result inincidental changes, such as vessel-generatedwaves that may increase shoreline erosion.Often, the human effects are an intentionalattempt to arrest the natural erosional anddepositional processes to maintain theshoreline in a fixed desired state for humanuse.

Intentional modifications to the Hudson

River Estuary have resulted from theestablishment of railways and roads on bothshorelines, filling of shallow areas,construction of bulkheads, installation ofmarinas and docking facilities, dredging tomaintain navigation channels, dredge spoildisposal, construction of dams on tributaries,introduction of invasive species of

vegetation, and other agricultural, urban andindustrial types of development. All ofthese activities cumulatively have changedthe estuarine habitats, both above andunderwater, so that they may not support therichness of ecological communities andprocesses that potentially could occur in theestuary.

The Hudson River National EstuarineResearch Reserve (Reserve) and the HudsonRiver Estuary Program (both part of theNew York Department of EnvironmentalConservation [NYSDEC]), in conjunctionwith the New England Interstate WaterPollution Control Commission, contractedASA Analysis & Communication (ASA)and Alden Research Laboratory, Inc.(Alden) to investigate options for restoringand enhancing shoreline habitat through twotypes of projects: softening hardenedshorelines (soft engineering) and stabilizingeroding shorelines.

Caulk et al. 2000 defines soft engineering asfollows. Soft engineering is the use ofecological principles and practices to reduceerosion and achieve the stabilization andsafety of shorelines, while enhancinghabitat, improving aesthetics, and savingmoney. Soft engineering is achieved by

Hudson River and Sugarloaf Mountain, Pollepel

Island and Breakneck Ridge beyond


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using vegetation and other materials tosoften the land-water interface, therebyimproving ecological features withoutcompromising the engineering integrity ofthe shoreline.

The project was completed by conductingthe following tasks:

review the available literature onshoreline stabilization methods.

field survey of the Hudson River Estuary

shoreline to qualitatively assess thecurrent types, condition, and function ofnatural and engineered shoreline habitatsbetween the Piermont Marsh and theTroy Dam. Information onanthropogenic, physical, hydrologic, andmeteorological conditions that could beimportant determinants of likelyrestoration success was also obtained.

selection of five example sites where

stabilization techniques could be used torestore ecological function and maintainhuman use activities (if appropriate)

analysis of the regulatory process for

conducting shoreline restoration projects

This report presents the literature review, asynthesis of the field survey results, and anevaluation of five examples of potentialshoreline restoration sites.

Section 2 Hudson River Estuary

Shoreline

Morphometry

The morphometry of the Hudson River has

been characterized by Central Hudson Gas

and Electric Corp. et. al. (1999) in the DEISfor Bowline Point, Indian Point 1 and 2, andRoseton Stations. For the purpose of theDEIS, the authors divided the river into fivesegments (Table 1).

Erosional Forces

Erosion, and its counterpart deposition, arenatural processes that determine, and aredetermined by the river morphology.Erosion occurs when the shear stress exertedon substrate particles is sufficient to liftthem off the substrate and suspend them inthe water column. Shear stress is the forceper unit area exerted on objects in or at theboundary layer of a moving fluid. Thestress is proportional to the velocitygradient, i.e. the rate of change of velocitywith distance from the bottom (Vogel 1994).Because the velocity required to suspend aparticle is higher than the velocity requiredto keep it in suspension, suspended particlesare typically transported by the flow tolocations where velocities are lower andsettling can occur.

Erosion can occur in the supratidal (riparian)

zone, the intertidal zone, and the subtidalzone. Above the high tide level, mosterosion will be wind or precipitation-induced on steep and/or unvegetated soils.Erosion of such areas can be reduced bydecreasing the slope, inducing vegetativeprotection, or covering with erosion resistantmaterials. However, storms or other eventscausing high water levels or strong waveaction can also cause erosion in this zone.


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Table 1 Hudson River Morphometry

Region Segment Characterization

Albany/Troy Dam,Catskill, Saugerties

RM 152 -94 Narrow with extensive shoals and 29 tributaries; theslope of the river bottom is greater in this segment than

others resulting in generally greater velocities The riverchannel is heavily modified due to navigationaldredging in early and mid 20

thcentury. Sediment

disposal was along shoreline or used to create artificialislands. Shorelines are highly modified with rock andtimber crib dikes to contain the dredge spoil.

Kingston, Hyde Park,Poughkeepsie,Cornwall

RM 93-56 Series of progressively deeper pools movingdownstream; its volume is more than 1.5 times that ofthe RM 152-94 stretch due to deep cutting of glaciers inthis constricted area; shallow shoreline and shoal areasare common in the southernmost end of the reach.

Shores are mix of rock, sand and soil, some of which isvegetated. There are numerous former industrial siteswith degrading shoreline structures. Shallow areas areoften vegetated with water chestnut, milfoil, or nativeaquatic vegetation.

Hudson HighlandsWest PointIndian Point

RM 55-39 Deepest and most turbulent stretch; river narrowsabruptly, bends sharply, and increases to depths over150 ft. Shorelines are either railroad bed, or bedrockthat slopes steeply to the river channel. Very littleshallow area exists in this segment, except on thelandward side of the railroad beds where there are

extensive tidal marshes, and in Peekskill Bay.Haverstraw BayCroton HaverstrawTappen Zee

RM 38-24 Short, broad (2.5 mi) stretch creating a broad, shallowbasin; this is the widest, shallowest section of river;extensive shoal and shore-zone areas; major depositionarea; sediments high in organic matter; biologicallyproductive area, particularly as a fish nursery area. Thewidth of the river and relatively low landforms alongthe shores make this the segment most impacted bynatural wave erosion.

Palisades, New YorkHarbor

RM 23- 0 Relatively straight, deep section with few shoals orshore-zone habitat; due to urbanization and industrial

development, the lower 12 miles has little remainingnatural shoreline, particularly along the east shore. Onthe western shore, Palisades escarpment hassignificantly hindered development and mostmodifications are those associated with rails andhighway rights of way.


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In the intertidal zone, the major erosiveforces are wind-induced waves, vessel-induced waves, and ice scour.

Figure 1 Tidal Zones

Wind-induced waves wind waves arethe result of the shear stress of airmoving over water. The shear stress onthe water surface induces watermovement along the surface in thedirection of the wind, and a subsurface

return current. Wave heights increasewith the wind velocity and distance overwhich the shear stress acts (fetch). As aresult, regions of the estuary which areless protected from winds by high landforms, and provide long uninterrupteddistances over which the wind can act,will be subject to stronger wave actionthan will more protected areas. Thusbroad areas of the estuary (e.g.Haverstraw Bay, Newburgh Bay) will be

subject to more wind-wave erosion thanwill narrow, more protected areas (e.g.West Point area).

Vessel-induced waves - Ship waves areinitially generated due to waterdrawdown. As a ship proceeds, itcreates a return current, offset by waterdepression the length of the ship, about

ft. The transition from depression toan undisturbed water level creates a frontwave. A similar wave is generated offof the stern, the back wave. Drawdowncreates a long solitary wave the length of

the ship. It is not easily observed in thefield. It does not break at the shoreline; itis more like a quick tide pulse.

Secondary waves are created by inertialforces. There are two sets of such waves.Transverse waves are perpendicular tothe sailing line; diverging waves are atan angle. These waves intersect. Theyare short, behave like normal waves, andbreak at the shoreline. These waveshave the potential to reach 1 ft in height.

Ship traffic is a major source of minorand major damage to shoreline structureson the Hudson River. For example, adock supported by concrete blocks atHenry Hudson Park was recently sodamaged by ship waves that it had to beremoved.

Wave energy is dissipated along ashoreline differently depending on theshoreline geometry. Waves impacting

shallow shorelines dissipate some energygradually as the wave travels up theshoreline. As the wave approachesshallow water, the wave form changes,becoming steeper and eventually breakswhen the wave crest speed exceeds thewave speed. Shorelines with steepslopes or vertical walls experience thefull force of the wave energy. The waveenergy is translated into high velocitiesup and down the wall which may scour

the material at the base of the wall.

Ice has been shown to be a significantmodifier of physical, chemical, andbiological conditions in rivers (Prowse2001a, Prowse 2001b). Driven by tides,river currents, and winds, the physicalaction of ice in the lower Hudson River


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is a primary geomorphic process. Banksand shallow substrates are scoured,moving sediments and removing manyorganisms. Ice rafts push, roll or slidematerial along tidal flats. Anchor ice

can break loose and carry along largechunks of material. These processesresult in localized areas of bankinstability, limited riparian andsubmerged aquatic vegetation, and areasof sediment deposition.

The severity of the disturbance variesannually with the timing and extent ofice floes. During the winter, the lowerHudson Estuary typically has areas ofopen water interspersed with areas of icethat oscillate with the tide. The upperEstuary can have ice locked into shore,with only the navigational channel open.During the spring, ice breakup results inrafts of ice (floes) flowing up anddownstream with the tide, which canform ice dams that hold back the flow ofwater.

In the shallower parts of the subtidal zone,waves and ice scour can be important

erosional forces, but outside the shallowareas water velocity due to the netdownstream and tidal currents are moreimportant. In the Hudson, the currents varyin magnitude and direction throughout thetidal cycle, resulting in continuously shiftingareas of re-suspension (scour) anddeposition. However, there are areas wherenet deposition occurs, which over time canchange the ecological community. Whendeposition interferes with human uses,

primarily navigation, then dredging isundertaken to restore desired water depths.But because of the dynamic processes oferosion and deposition, dredging is only atemporary solution.

The boundaries of the supratidal, intertidal,and subtidal zones are determined by themean sea level. If sea level rises, as is

predicted if global warming occurs, then thezone boundaries will be shifted to higherelevations and the importance of the variouserosional forces along any particular area ofthe shoreline will change. Higher mean sea

level could lead to inundation of low-lyingcoastal regions, more frequent flooding dueto storm surges, and worsening beach(shoreline) erosion (IPCC 1996). Such risesmay have a number of impacts on the tidalportion of the Hudson River, such as:

Shift of wave erosion and ice scour intopresently supratidal zone

Increase in use of hardened shorelinestructures to arrest the increase in wave

erosion. Increased water depth over shallow

water zones

Further upstream penetration of the saltwater into presently freshwaterenvironments

Ecological Communities

As is typical in temperate estuaries, theHudson River Estuary contains a number of

different community types that have thecommon characteristic that they are tolerantof a wide range of environmental conditions.In the Hudson, water temperatures can rangefrom 0 C to 30 C or above in nearshoreshallows. Salinities range from 0 ppt to >10ppt depending on location and freshwaterinflow. Nutrients, sediment, and pollutantinputs occur in pulses when precipitationcauses surface runoff and high tributaryinflows.

Nearshore communities in the estuary mustcope with cyclical inundation due to tides,and with very high physical energy inputs.These high energy inputs play a large role indetermining the nearshore community type.To exist in the nearshore environment,plants and animals must be able to withstandthe bi-directional tidal flows, the battering of


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waves generated by storms on anintermittent basis, and by vessel traffic (bothrecreational and large commercial vessels)on a more regular basis. Physicaldisturbances also result from the transport of

large woody debris into the nearshore areaduring high flows, and from scour of icefloes and tidal movements of ice sheets inthe winter. This physical energy which isdissipated in the nearshore environmentmakes the substrate very changeable andoften leads to erosional processes in theintertidal areas.

Edinger et al. (2002), expanded uponReschkes earlier (1990) catalog ofecological communities to describe 24estuarine ecological communities in NewYork, 15 of which occur along the HudsonRiver Estuary. Ten of these are naturalcommunities:

tidal river

brackish subtidal aquatic bed

freshwater subtidal aquatic bed

brackish tidal marsh

brackish intertidal mudflats

brackish intertidal shore

freshwater tidal swamp

freshwater tidal marsh

freshwater intertidal mudflats

freshwater intertidal shore

Five of the communities are artificial orcultural:

estuarine submerged structure

estuarine channel/artificial impoundment

estuarine impoundment marsh

estuarine dredge spoil shore

estuarine riprap/artificial shore

The freshwater communities typically havesalinities below 0.5 ppt and occur north ofNewburgh (RM 60), while brackishcommunities have salinities usually above0.5 ppt and occur primarily south of

Newburgh.

These distinct communities are determinedby their physical characteristics, and by theplant and animal species that thesecharacteristics will support. Generally,plants are determined by the conditions oflight, wind, moisture, salinity, nutrients,substrate, and frequency and severity ofdisturbances. Plants provide food andshelter, and modify the environment in waysthat are beneficial to the animals that typifythe community. However, there are alsoother factors that determine the animalcomponent of the community. Both theaquatic and terrestrial communities of theestuary have resident and migratory fauna.The resident fauna, which are permanentyear-round members of the community, aredetermined by the overall suitability of thehabitat for all life functions, includinggrowth, survival, and reproduction. Themigratory fauna, (e.g. fish such as Americanshad, blueback herring, striped bass, bayanchovy, and migratory birds such as robins,hummingbirds, ducks, and some raptors) usethe estuary only for some of these functions.

Habitats & Communities

The river provides several distinct types ofhabitats (combinations of depth, currentpattern, and substrate) which, incombination with water salinity, determine

community type:

Shallow basin and backwater areas -

promote settling of suspended organicmatter. Such areas support freshwater orbrackish subtidal aquatic bedcommunities. In freshwaters, rootedvegetation is composed of rooted standsof water celery, pondweed, waterweed,


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and naiads (Edinger et al 2002). Theexotics water chestnut and Eurasianmilfoil may also be present. The plantsslow the flow of water, promotesedimentation, and support invertebrates

such as oligochaetes, isopods,amphipods, and chironomids (BoyceThompson Institute 1976). Theinvertebrates and cover provided by thevegetation support fishes, primarilyyoung, of white perch, spottail shiner,striped bass, various members of thesunfish family, and others. In brackishareas the common plants are sagopondweed, horned pondweed,waterweed, coontail, and the exotic

Eurasian milfoil. The same groups ofinvertebrates, although typicallydifferent species, but also decapods(crabs) and mollusks inhabit the beds,providing food for the fish fauna.Common fishes include striped bass, andbay anchovy. The plants, invertebratesand fish, attract birds such as canvasbackduck, bufflehead, common goldeneye,merganser, greater scaup, snowy egret,and great blue heron (Edinger et al

2002).

Exposed shoreline shoreline areasadjacent to deeper water are higherenergy environments in which organicmatter is scoured, leaving primarily sandand gravel substrates. These areastypically support the brackish andfreshwater intertidal shore communities,and the estuarine riprap/artificial shorecommunity, which are less vegetatedthan the aquatic bed communities,although some of the same species maybe present. Due to the shallower waternearshore, wave action and ice scour aremore severe than for the deeper aquaticbeds, Invertebrates, particularlyisopods, amphipods, and mollusks arecommon. In freshwater portions of theestuary, the zebra mussel is commonly

found on hard substrate. Fishescommonly found in these communitiesare striped bass, white perch, Americanshad, blueback herring, and alewife.

Shallow shore zone areas with rooted

aquatic vegetation- provide substantialcover and protection for invertebratesand small fishes. These habitats includethe brackish tidal marsh, brackishintertidal mudflats, freshwater tidalswamp, freshwater tidal marsh,freshwater intertidal mudflats, andestuarine impoundment marshcommunities. These shallow nearshoreenvironments, can be natural or artificial(many were created when the rail linescut off small embayments from the mainriver). The plants present depend on thedegree of inundation, salinity, andnearby terrestrial communities. Thestability of these shallow shore zonecommunities is determined by the landuse and sediment loads from thelandward side, and the amount of waterexchange with the river proper. Fornatural communities, water exchange istypically not a limiting factor, but for theartificially created communities, such asthose cut off from the river by railroadbeds, flushing can affect the rate ofsediment accumulation and amount offaunal exchange with the river.Common fishes include mummichog,killifish, and other shallow-waterspecies.

Deep water areas with relatively high

velocities- contain deep, turbulent

currents that keep sediments insuspension. These areas are classified astidal river communities. The bottom maybe hard or soft and there is littlevegetation because of the depth,turbidity and strong currents. Infreshwater areas of the estuary hardbottom habitats are infested with zebra


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mussels, which obtain densities highenough to filter large portions of thewater. They have been hypothesized toremove enough organic matter from thewater column to lessen habitat suitability

for pelagic fishes, and raise thesuitability for benthic and shore zonefishes (Strayer et al 2004). Commonfish species in these zones are Atlanticand shortnose sturgeon, hogchoker,American eel, Atlantic tomcod,American shad, blueback herring,alewife, and bay anchovy. Somespecies, such as striped bass andAmerican shad are pelagic spawners,which release their eggs in these areas

and the eggs and early larvae drift in thewater currents until they hatch and thelarvae have developed swimmingcapabilities.

Habitat Modifications

Physical alterations to the estuary have beenongoing for centuries, resulting in changesto the natural ecological communities (e.g.freshwater subtidal aquatic bed to estuarinedredge spoil shore). Often, these alterationsare undertaken to control the naturalerosional processes that are constantlytaking place in the high-energy nearshoreareas, resulting in hardened shorelines.Other prime reasons for alterations arereversal of natural depositional processesthat occur in the river, i.e. dredging, andcreation of new terrestrial habitat (filling) asa way to dispose of dredge spoil or for otherreasons.

On the Hudson River, significant habitatimpacts have resulted from:

hardening of the shoreline withbulkheads and other erosion controlstructures- changing intertidal shorecommunities to riprap/artificial shorecommunities.

navigational channel dredging- changing

shallow tidal river habitat and aquaticbed communities to deepwater tidal rivercommunities. Disposal of the sedimenthas lead to creation of dredge spoil

shoreline and terrestrial communities.

filling of low-lying areas includingwetlands- changing swamp and marshcommunities to cultural terrestrialcommunities.

clearing of land for human uses converting natural terrestrial habitats tocultural terrestrial habitats

constructing transportation infrastructure railroad and road construction andculverts - changing the flow of surfacewater, causing changes to wetlands,fragmentation of habitats

Shoreline Hardening

Shoreline hardening is very common alongthe estuary shore, and is the main type ofmodification being addressed in this project.Examples of shoreline hardening includebulkheads, jetties, boat ramps, railbeds, and

other solid structures that have been used tostabilize Hudson River shoreline areas. Thepredominant materials used to build thesestructures on the Hudson River include:

Rip rap

Rock cribs

Steel sheet pile

Stone masonry

Timber bulkheads

Large unsecured stones

Concrete

In addition, buildings and impermeablesurfaces (roads, parking lots) are often builtbehind the shoreline structures. Thesestructures and accompanying shorelinedevelopment have a variety of impacts on


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the water column, submerged aquaticvegetation (SAV), wetlands, and soft bottomfeatures. These impacts include:

Reflection of wave energy off ahardened shoreline accelerates subtidalerosion and leads to loss of intertidal softbottom habitat.

Increases in turbidity in the watercolumn.

Deepening of near shore habitat and

elevated turbidity deters futurecolonization of wetland or SAV plants.

Decreases in habitat complexity result inreduced fish and invertebrate use of ahardened shore.

Preservatives in timbered bulkheads thatcan be toxic to living organisms.

Losses of wetland habitat behind

structures due to filling or reduced waterexchange.


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Section 3 A Synthesis of Literature

on Shoreline Stabilization Methods

and Habitat Enhancements

Applicable to the Hudson River

Estuary

Review of Available Literature

Applicable to the Hudson River

The Hudson River is a tidal estuarine riverthat experiences fluctuations in water levelsand velocities. As a result, any softtechnique designed to replace an existinghardened shoreline must be capable ofwithstanding existing forces. In addition to

high current velocities, consideration needsto be given to tidal flows that reverse withebb and flood tides, commercial shippingand small boat traffic, ice floes and heavydebris loads that exist in much of the riverenvironment. The hardened shorelinestypically provide critical stabilization ofinfrastructure (roads, railroad beds, bridgeabutments, dredged spoil, etc.) andprotection against these forces.

River bank stabilization techniques found inthe literature which have the potential toimprove aquatic habitat for fish werereviewed. Initially, information on allavailable techniques was reviewed. It wasfound that the majority of the literaturedescribed restoration techniques appropriatefor small fresh water rivers and streams.However, some of the techniques weredeemed to be potentially appropriate for thetidal Hudson River Estuary.

The literature search was performedelectronically. Reference databases thatwere queried include:

Ingenta

EBSCOHost

Scientific Research

Illumina

Engineering Village

USACE

ASCE

NRCS

University reference libraries (University ofMassachusetts and Pennsylvania StateUniversity) were accessed to obtainreferences that could not be obtaineddirectly off the internet. The keywords usedto query the data bases include:

River restoration

River bioengineering

Soil bioengineering

Streambank stabilization

Biotechnical streambank stabilization

Ecological river restoration

Estuarine river restoration

The search yielded a list of citations andabstracts for documents identified by thekeywords. Much of the information ontechniques applicable to the Hudson Rivercame from a number of comprehensive

review documents (FISRWG 1998, USDANRCS 1996, GSWCC 2000, Allen andLeech 1997, Gray and Sotir 1996, Schiechtl1980, Schiechtl and Stern 1997, Landphairand Li 2002).

Table 2provides a comprehensive review ofall available stabilization methods. Aldenassessed this information to:

identify the relative advantages and

disadvantages of each alternative, and

determine the alternatives that have thegreatest potential for application on theHudson River Estuary.

Factors considered in accessing the relativeadvantages and disadvantages of theavailable stabilization techniques included:

cost and simplicity of installation


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manual versus mechanized construction

maintenance requirement

longevity of technique

rate of stabilization (immediate versus alonger time needed for plant growth)

applicable slopes

susceptibility to ice and debris damage

space requirements

aesthetics

habitat function

tidal flow

Allowable shear stress (based on velocity)was the primary criterion for determiningwhether a given soft engineering river bankstabilization technique was applicable forthe Hudson Estuary. For the purposes ofthis project, the limiting shear stress for riprap with an average diameter of 6 inches (6inch d50) was chosen as the minimumdesign criteria. This size is considered to bethe minimum size riprap that would be usedon a large river like the Hudson with a bankslope equal to or less than 1:2 (V:H). Table

3(Fischenich 2001) provides stabilitythresholds for a variety of bank restorationmaterials.

All available alternatives were qualitativelyassessed. Candidates for Hudson River usewere selected based on the information inTable 2and Table 3. The alternativeschosen will withstand shear stresses greaterthan 2.5 lbs/ft2(6 inch d50 rip rap). All areintegrated systems that incorporate hardstabilization features for soil stability andsoft features that enhance the habitatfunction:

Vegetated Geogrids

Live Crib Wall

Joint Plantings

Brush mattresses

Vegetated Rock Gabions or Mattresses

Each of these techniques (highlighted inTable 1) is presented in detail in the nextsection.


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Table 3 Permissible Shear Stress and Velocity for Selected Lining Materials (Fischenich

2001)

Boundary Category Boundary Type

Permissible

Shear Stress

(lb/ft2)

Permissible

Velocity (ft/sec)

Vegetation Class A turf 3.7 6-8

Class B turf 2.1 4-7

Class C turf 1 3.5

Long native Grasses 1.2-1.7 4-6

Short native grasses and bunchgrass

0.7-0.95 3-4

Reed plantings 0.1-0.6 N/A

Hardwood tree plantings 0.41-2.5 N/A

Jute net 0.45 1-2.5Temporary Rolled

Erosion ControlProducts (RECPs) Straw net 1.5-1.65 1-3

Coconut fiber with net 2.25 3-4

Fiberglass roving 2 2.5-7

Non-Degradable RECPs Unvegetated 3 5-7

Partially vegetated 4.0-6.0 7.5-15

Fully vegetated 8 8-21

Riprap 6 inch D50 2.5 5-10

9 inch D50 3.8 7-11

12 inch D50 5.1 10-13

18 inch D50 7.6 12-16

24 inch D50 10.1 14-18

Soil Bioengineering Wattles 0.2-1.0 3

Reed fascine 0.6-1.25 5

Coir roll 3-5 8

Vegetated coir mat 4-8 9.5

Live brush mattress (initial) 0.4-4.1 4

Live brush mattress (grown) 3.90-8.2 12

Brush Layering (initial/grown) 0.4-6.25 12

Live fascine 1.25-3.10 6-8

Live willow stakes 2.10-3.10 3-10

Hard Surfacing Gabions 10 14-19

Concrete 12.5 >18


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Alternative Shoreline Stabilization

Methods

A review of literature published on each ofthe shoreline stabilization systems that are

deemed applicable to the Hudson River ispresented in the following sections.

Vegetated Geogrid

The following information was taken fromGray and Sotir 1996, Li and Eddleman2002, Allen and Leach 1997, USDA NRCS1996, and Sotir and Fischenich 2003.

A vegetated geogrid is a system ofsuccessive soil lifts wrapped in a synthetic

material with live branch cuttings placedbetween layers. The system provides rapidvegetation growth following installation.The vegetation acts as a buffer to reduce therivers energy and shear stress at the soilsurface. The synthetic mesh adds additionalstrength to anchor and prevent soil erosion.Once the live cuttings become established,the root systems intertwine with the geogridbinding the system together (Gray and Sotir1996). The design is based on a dual fabric

system adapted from synthetic reinforcedretaining walls used for bridge abutmentsand road embankments (Allen and Leach1997). A section of the system is shown onFigure 2(USDA NRCS 1996).

The materials for the live branches consistof willow, dogwood or woody plants thatpropagate roots easily. The branches aretypically to 2 inches in diameter andextend to the back of the geogridreinforcement. The geogrid material is

made of a synthetic polymer selected basedon allowable tensile strength and providesthe primary reinforcement (Gray and Sotir1996).

The geogrid system is constructed byexcavating the bank and installing a rockfooting to the mean high tide water depth.

The footing should extend down to theexpected scour depth. Typically, two lifts ofrock wrapped in geogrid are adequate for therock footing. Live branch cuttings areplaced in a crisscross pattern so that the tips

extend just beyond edge of the slope inbetween each soil lift of 6 to 8 inches thick(Gray and Sotir 1996). The first soil lift isplaced over the branches and rock footingand compacted (USDA NRCS 1996).Burlap strips or geotextile fabric about 4 ftwide should be placed at the slope face tocontain the soil, and the soil should besuitable for plant growth. Forms can beused to protect the fabric while compactingfor each lift. Each layer can be keyed into

the previous layer with stakes or rebar. Theupstream and downstream end of thetreatment should be protected with ahardened structure or carefully tied into theexisting vegetation to prevent flanking orerosion around the ends (Allen and Leach1997).

Vegetative geogrid installations have beenused mainly on relatively small rivers andstreams and must be used with caution onthe Hudson River. The expected shear stressand velocity thresholds for a fullyestablished vegetative system are 8 lbs/sq ftand 14 ft/sec, respectively, as shown inTable 4. The system should be inspectedafter the first couple of floods and monitoreduntil the vegetation has become established(Sotir and Fischenich 2003). The systemshould also be inspected in early spring afterlarge ice floes.


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Table 4 Stress and Velocity Levels for Vegetated Geogrid (Sotir and Fischenich 2003)

Time Velocity (ft/sec) Shear Stress (lb/ft2)

Initial (immediatelyafter construction) 3-5 5-9

Established (after 1 to2 years of growth)

8 14

Figure 2 Vegetated Geogrid (USDA NRCS 1996)


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Live Crib Wall

The following information was taken from:Gray and Sotir 1996, Li and Eddleman2002, Allen and Leach 1997, USDA NRCS

1996, GWSCC 2000, Donat 1995, andSchiechtl 1980

A live crib wall is a reinforced earthensystem that consists of timbers andvegetative cover. The timbers are arrangedin a box pattern creating structural cribs thatare filled with suitable fill and layers of livebranch cuttings. The live cuttings extend tothe native soil behind the crib structure andthe root systems intertwine with the crib

binding the system together once the livecuttings become established (Gray and Sotir1996). A detail of a live crib wall is shownon Figure 3.

The materials for the live branches consistof willow, dogwood or woody plants thatpropagate roots easily. The branches aretypically to 2 inches in diameter andextend to the back of the crib. The inertmaterials consist of untreated timbers or logsranging from 4 to 6 inches in diameter with

the varying lengths to suit specific siteconditions (USDA NRCS 1996).Prefabricated concrete, steel or plastics arealso used as crib material (Donat 1995).

The crib wall is constructed by excavatingthe river bank down to the expected scourdepth. The first level of timbers is placed ona rock footing which extends into the riverto provide toe protection from scour. Thesetimbers are placed in two continuous rowsparallel with the shoreline andapproximately 5 ft apart. The next level oftimbers are placed perpendicular to and ontop of the first level creating a crib patternsecured with spikes or rebar dowels. Thetoe of the wall is typically protected fromscour with rocks. The wall is battered at anangle towards the shore approximately 6:1(V:H) or greater to provide additional

stability (Gray and Sotir 1996). The crib isfilled with rocks to the base flow waterlevel. Above the base flow water level,layers of live branch cutting and compactedsoil are installed between each level of

timbers. At least 10 branch cuttings shouldbe used per running meter. The soil aroundthe live cuttings must be protected fromwashout at the wall face by carefully placedbranch packing or rock placement. If thepacking is too tight, vegetation developmentcould be hindered (Schiechtl 1980). Theupstream and downstream end of the cribwall should be protected or keyed into theexisting slopes to prevent flanking (GSWCC2000).

Live crib walls have been used mainly forstreams and small rivers but could beapplicable to the Hudson River. Crib wallscreate a steep slope, which require less spacewhile providing a natural lookingappearance. Additional support, such astiebacks to deadmen anchors, may berequired depending on the height of the wall.

The Hudson River currently has manytimber bulkheads. A live crib wall may be a

suitable alternative under the proper siteconditions. The timbers used for the crib-wall, often eastern white cedar, red pine,jack pine, or spruce (Heaton et al. 2002), areuntreated to avoid adverse environmentalimpacts. Therefore, the lifespan of thesematerials will be less than treated timbers.


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Figure 3 Live Crib Wall (USDA NRCS 1996)

Joint Planting

The following information was taken fromSchiechtl 1980, USDA NRCS 1996,GSWCC 2000, and Donat 1995

Joint planting involves adding vegetation(live stakes) to an existing stone or riprapslope or creating a vegetated rock slope.Live stakes are tamped into joint spacesbetween the rocks. The slope should begraded similar to the natural river bank slope

(Schiechtl 1980). A detail of a joint plantingsystem is shown on Figure 5.

The materials for joint planting consist ofwillows or woody plants that propagateroots easily. The live stakes should be 2 to 3inches in diameter and 3 to 3.5 ft in length(GSWCC 2000). The live stakes should beinstalled the same day they are cut or

carefully stored for installation. The rockshould be sized appropriately for the slopeand the hydraulic river conditions.Prefabricated cellular concrete cells can beused as an alternative to riprap to stabilizethe slope. The concrete cell structure offerssimilar slope protection with vegetation inthe voids of the cellular grid, as shown onFigure 6.

Construction of a new joint planting systemrequires excavation of the river bank below

the expected scour depth and installation ofa rock footing that extends into the river toprovide toe scour protection. The rockshould be placed loosely or hand placed at aslope similar to the natural stream bank nothicker than 2 ft (GSWCC 2000). Two toten healthy live cuts per square meter shouldbe placed perpendicular to the rock slope


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and hand tamped (Donat 1995). The livestakes should be installed to two-thirds theirtotal length into the soil beneath the rockwith the end slightly protruding from therock face. A steel probe or rebar may be

used to prepare a pilot hole through theriprap bed to ease installation of the livestakes (USDA NRCS 1996).

The joint planting technique can also beused for existing riprap slopes. Live stakeswould be installed on the existing riprapslope similar to that described above. If theriprap layer is too thick suitable soil willneed to be added in the voids to supportvegetation growth. Soil would be added toslopes with armor layers greater than 3 to 4ft. Dredged material may be suitable for thisapplication.

The Hudson River Estuary has shorelineswhere the joint planting technique isnaturally occurring. Portions of the HudsonRiver banks were stabilized using riprap inthe late 1800s and early 1900s. Many ofthese shorelines have not been maintained

and have since overgrown with vegetationwhile maintaining a stable river bank. Theseexisting shorelines (Figure 4) are goodexamples of the desired end product for thejoint planting technique.

Live stake installations should be monitoreduntil the stakes take root and inspected aftermajor storms and floods. The amount ofvegetation can be increased considerably ifpruned and fertilized during the secondseason (Schiechtl 1980).

Rough rock surfaces and flexible branches,slow water velocities and reduce shearstresses near the river bank. Theseconditions allow for additional vegetation

growth on the river bank. The vegetationcreates shade for the river and may reducewater temperature, improving aquatichabitat. Joint planting could be a valuabletool for enhancing habitat in the HudsonRiver Estuary due to the dominance ofhardened riprap in modified shoreline areas.

Figure 4 Existing Shoreline (similar to Joint Planting design)


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Figure 5 Joint Planting (USDA NRCS 1996)

Figure 6 Vegetative Cellular Concrete Block (USDA NRCS 1996)


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Brush Mattress

The following information was taken fromAllen and Fischenich 2000, USDA NRCS1996, and GSWCC 2000.

A brush mattress is a mat of intertwined livebranches covering a river bank with a livefascine (live cutting materials) over a rockbase. The brush mattress is secured withwire or twine, live stakes, and stout deadstakes. The live sprouting plants act toreduce the river velocity and shear stressalong the shore, and encourage sedimentdepositions at high water levels (Allen andFischenich 2000). The system creates an

interlocking network of roots that anchor theslope in place. A detail of a brush mattressis shown on Figure 7.

The live cutting materials for brushmattresses consist of live branch cuttings ofwillows, viburnum, shrub dogwood, orsimilar plant species that propagate rootseasily. The branches should be 2 to 3 yearsold, to 1 inches in diameter and 5 to 10ft in length. Riprap is typically used for thebase and the live fascines consist of bundles

of live cut branches partially buried in atrench near the base of the slope. Thematerial for the wire could be coir bristletwine, tie wire or similar.

Construction of the brush mattress systembegins with excavation of the slope base toinstall a rock base. The rock should extendinto the river channel to provide scourprotection at the toe of the slope and shouldcontinue upslope to the low water level.The remaining bank should be graded at aslope of 1:2 (V:H) or flatter. The livefascine would be installed in a trench 8 to 10inches deep located adjacent to the top of therock base and would be sloped to reduceerosion and pooling of water upslope of the

fascine (Allen and Fischenich 2000). Thefascine bundles are typically 6 to 8 inches indiameter with the basal ends pointing in thesame direction in the trench. The bundlesare wrapped with twine every foot along the

length. Brush cuttings are placed with basalends pushed into the live fascine. Deadstout stakes are installed in a grid patternabout 3 to 5 ft apart with wire attachedbetween stakes securing the brush cuttingsin place. The brush mattress and livefascine are covered with soil that is workedinto the branches by tamping to create goodstem to soil contact (Allen and Fischenich2000). The system could be lightly wateredto assist soil compaction and stem soil

contact.

Maintenance requirements will varydepending on site conditions and thefrequency of storm events and floods. Thebank should be monitored regularly andrepaired as necessary until the vegetationhas taken root and become well established.The upstream and downstream ends of thetreatment should be monitored for scour andmay require more substantial treatments toprevent flanking.

Applications of brush mattresses have beenused for relatively small rivers and streams.Expected shear stress and velocitythresholds are 4-8 lbs/sq ft and 12 ft/sec,respectively, for brush mattresses fullyvegetated with rock toe protection, as shownin Table 5. The thresholds for non-vegetated brush mattresses just afterconstruction are much less and should beclosely monitored until the vegetation

becomes established. The ability of thisoption to protect the bank from ice damageis limited (USDA NRCS 2002).


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Table 5 Stress and Velocity Levels for the Brush mattress (Allen and Fischenich 2000)

Brush mattress type Velocity (ft/sec) Shear Stress (lb/ft2)

Staked only w/o rockbolster at toe (initial) < 4.0 0.4 - 3.0

Staked only w/o rockbolster at toe (grown)

< 5.0 4.0 - 7.0

Staked only w/rockbolster at toe (initial)

< 5 0.8 - 4.1

Staked only w/rockbolster at toe (grown)

< 12 4.0 - 8.0


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Figure 7 Brush Mattress (USDA NRCS 1996)

Vegetative Rock Gabions

The following information was taken fromFreeman and Fischenich 2000, USDANRCS 1996, Gray and Sotir 1996, andMaccaferri 2005,

Vegetated rock gabions are galvanized wirebaskets, filled with rock or fill material andstacked along the river bank with live

cuttings placed in between the rock gabions.The rock gabions are tied together toprovide bank slope protection at sites thathave limited space and require a steep bankin excess of 1:1.5 (V:H) (Freeman andFischenich 2000).

The live cutting materials for vegetativegabions consist of live branch cuttings ofwillows, viburnum, shrub dogwood or


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similar plant species that propagate rootseasily. The branches should be to 2 inches in diameter and long enough to reachthe soil behind the gabions (USDA NRCS1996). The wire baskets could be made of

galvanized or plastic coated welded wire orwoven wire mesh. Recently, high strengthplastic material (Tensar) has also been usedfor baskets (Freeman and Fischenich 2000).The gabion fill typically consists of rocksizes ranging from 4 to 9 inches (USDANRCS 1996) and select fill capable ofsupporting vegetation growth (Gray andSotir 1996).

Construction of a vegetated gabion wallstarts by excavation of the bank to a levelbelow the expected scour depth andpreparing a footing at an angle slightly tiltedinto the bank. Wire baskets are placed onthe footing, tied together with wire, andfilled with rock. The wall width at the basemay need to be two or more gabion basketswide depending on the wall height. As arule of thumb, the minimum base width toheight ratio is 0.5 (Gray and Sotir 1996),however, a professional engineer shouldapprove the design. A thin layer of earthenbackfill and live branch cuttings are placedperpendicular to the slope at the top of eachrow. The butt end of the branches extendsinto the backfill behind the gabions and theother end protrudes a few inches beyond thewall face (Gray and Sotir 1996).

Alternatively, the rock gabion baskets couldbe placed on the river bank slope, similar toa riprap design, with live stakes andbranches placed between the basket joints(Figure 9). This type of installation is called

a gabion mattress or Reno mattress.

Maintenance of the vegetated gabion wallmust include inspection of the wire basketsfor damage. Any broken or bent wiresshould be repaired. According to Freemanand Fischenich (2000), large woody treegrowth within the baskets should be cut toprevent damage to the gabion wires.However, other authors (Gray and Sotir1996) encourage growth within the gabionsto help anchor the wall. Maintenancerequirements are site specific and depend onthe relative risks associated with gabion wirefailure. A wall that is considered low riskcould allow large woody vegetation to growwithin the gabions, while a high risk wallwould require removal of the growth. Thetoe of the bank should be inspected for scourand the wall should be checked for bulgingand repaired as necessary.

Site conditions should be reviewed to

determine the applicability of the gabionwall for stabilizing a river bank. Table 6provides critical shear velocity values forvarious rock gabion designs (Chaychuk2005).


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Table 6 Allowable Velocities for Rock Gabions (Chaychuk 2005)

TypeThickness

(ft)

Filling StoneRange

(inches) D50 (inches)

CriticalVelocity1(ft/sec)

LimitVelocity2(ft/sec)

Mattress 0.5 3 4 3.4 11.5 13.8

Mattress 0.5 3 6 4.3 13.8 14.8

Mattress 0.75 3 4 3.4 14.8 16

Mattress 0.75 3 6 4.7 14.8 20

Mattress 1.0 3 5 4 13.6 18

Mattress 1.0 4 6 5 16.4 21

Basket 1.5 4 - 8 6 19 24.9

Basket 1.5 5 - 10 7.5 21 26.2

1. Velocity at which the revetment will remain stable without movement of rock fill.

2. Velocity which is still acceptable although there is some deformation of the protections due tomovement of the stones within the wire baskets.


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Figure 8 Vegetative Rock Gabion Wall (USDA NRCS 1996)

Figure 9 Vegetative Rock Gabion Mattress (Allen and Leech 1997)


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Applicability (of) Existing Shorelines

The techniques identified in the literaturereview could be used to stabilize naturaleroding shorelines. The efforts would be

similar to those identified for stabilizingfailing and eroding hardened shorelines. Forexample, stabilizing a failing concretebulkhead wall would require: 1) thebulkhead wall to be removed, 2) bank re-graded, and 3) installation of therecommended soft engineering treatment.Stabilizing a naturally eroding shorelinewould involve similar efforts: 1) bank re-graded, and 2) installation of therecommended soft engineering treatment.

Vegetation for Stabilization Methods

The following information was taken fromNRCS 1996, Adams 2002, and Hoag andLandis 2001.

All the river bank stabilization methodsutilize vegetation as a long term componentto stabilize the river bank. Rapid re-vegetation following construction isessential for a successful bank stabilization

project. Therefore, the most common andcost effective methods for re-vegetatingshorelines utilize dormant, non-rooted,branched hardwood cuttings (Hoag andLandis 2001). Benefits associated withusing cuttings for bioengineering soilstabilization techniques include:

1. stability of cutting when exposed to highcurrent velocities

2. an ability to plant in areas where the

water table is deeper than 30 cm3. lower costs than traditional bare root or

container nursery stock

The plant families most commonlyreferenced in the literature forbioengineering systems include:

Willows

Viburnums

Dogwoods

The plant species chosen for a projectshould be carefully selected based on the

following criteria:

Native plants

Availability, (the plants may be obtained

from a local nursery or harvested from anearby stand)

Rooting ability from cutting (integrity ofthe stabilization structures depend on thesuccessful establishment of theplantings)

Growth rate (rapid growth rate will limitthe systems vulnerability to floods andheavy storm events immediately afterinstallation while vegetation is becomingestablished)

Spread potential (density of vegetation

will benefit the systems integrity)

Salinity tolerance (bank vegetation willbe exposed to brackish water in lowerregions of the estuary)

Flood tolerance (bank vegetation will besusceptible to high currents and waterlevels during floods)

Costs (cost will vary depending on

location, species and type of planting)

Maintenance requirements (maintenance

requirements will depend on how wellthe plants meet the criteria above; e.g.easily propagated roots, rapid growthrate, high establishment speed, good

spread potential, and good salinity andflood tolerance will minimize the degreeof maintenance required)

Appendix B lists suggested woody plants forthe proposed restoration efforts. Theseplants are available commercially, can berooted from cuttings, and are native to theUS and already found in New York. This


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list is subset of the species listed in NRCS1996 Appendix 16B).

If possible, the plant species selected shouldalso represent the characteristics of naturalassemblages in the area. However, projectsare susceptible to invasion of aggressive,non-native plants that can establish coverover the project site (Adams 2002). Theplants selected for the project should beselected, planted, monitored and maintainedto limit the establishment of invasivespecies. Invasive riparian plants common tothe Hudson valley include:

Purple loosestrife (Lythrumsalicaria)

Common Reed (Phragmitesaustralis)

Japanese Knotweed (Polygonumcuspidatum)

Invasive aquatic plants common to theHudson are:

water chestnut (Trapa natans)

Eurasian watermilfoil (Myriophyllumspicatum)

Costs

Soft river bank stabilization techniques aretypically much less expensive thantraditional hard stabilization methods (Allenand Leech 1997). However, there is widevariability in the cost of plantings, inertmaterials and labor, depending on locationand complexity of the alternative. Due totheir greater stability, the techniquesselected for possible Hudson River Estuaryapplication tend to be more costly than othersoft techniques that are suitable for smaller,ice-free rivers and streams with lower waveenergy profiles. Therefore, the relative costcomparison below is between techniquessuitable for the Hudson River.

The available literature contains areasonable amount of information on theapproximate unit capital costs and relativecosts of the different techniques. Asummary of the published cost data for

techniques appropriate to the Hudson Riveris provided in Table 7. Additional laborrequirements for various bioengineering, asprovided by Fischenich and Allen 2000, areprovided in Table 8. This information canbe used to estimate the labor requirements ofvarious soft engineering installation tasks.

Vegetative Geogrids

The cost of using vegetative geogrids ismoderate to high compared to othermethods. The labor required for installationis about 1 man-hour per linear foot of treatedbank and typically accounts forapproximately 66 percent of the total projectcosts (Allen and Leech 1997).

Live Crib Wall

The capital costs associated with installing alive crib wall for protection are consideredmoderate to high compared to other methods

(Li and Eddleman 2002).

Joint Planting

The capital cost to install joint planting isconsidered low compared to other methods(Li and Eddleman 2002). The cost will besignificantly lower if the application is for aslope already protected with stone comparedto installing the entire system (stone and all).

Brush Mattress

The cost of a brush mattress is low andrequires 2 to 5 man-hours per square meter.The Waterways Experimentation Station(WES) reported a rate of 1 square meter perman-hour for a project constructed bystudents using hand tools. The rate includedharvesting brush, cutting branches and


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constructing mattresses (Allen and Leech1997).

Vegetative Rock Gabions

The cost of vegetative rock gabions are highcompared to other techniques. The cost ofthe wire gabion baskets (without stones)

range from $1.50 - $2.30 each (Freeman andFischenich 2000).

Table 7 Approximate Costs of Riverbank Stabilization Technique1

StabilizationTechniques

UnitCapitalCosts Reference

Relative CostAssessment

VegetatedGeogrids

$16 - 37per squarefoot

Sotir andFischenich 2003

High

Live Crib Wall$13-33 persquare foot

Gray and Sotir1996

High

Joint Planting$1 5 persquare foot

2Gray and Sotir1996

Medium

Brush Mattress$3 - 14 persquare foot

Allen andFischenich 2000

Medium

Vegetated RockGabions

$176 527per cubicyard ofprotection

Freeman andFischenich 2000

High

1.

For comparison, all costs were adjusted to 2005 $ due to inflation.

2. Does not include riprap and assumes 4 cuttings per square yard.


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Table 8 Vegetative and Bioengineering Labor Estimates (Allen and Fischenich 2000)

Activity Labor Required

Wattling 2-5 m/hr

Brush Layering 2-5 m/hrDormant Posts 0.2 - 1.0 m2/hr

Willow Cuttings 45 - 50 cuttings/hr

Plant Roll 6 m/hr

Coconut Fiber Roll 1.5 m/hr

Sprig Planting 4.0 - 20 m2/hr

Seedling Planting 30 - 120 plants/hr

Ball and Burlap Shrubs 10 - 25 plants/hr

Containerized Plants 20 - 40 plants/hr

Vegetative Geogrids 0.2 - 0.4 m/hr

Seeding 0.02 - 0.2 ha/hr

Hydroseeding 0.05 - 0.15 ha/hr


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Section 4 Estuary Shoreline River

Surveys and Selection of Shoreline

Restoration Sites for Case Studies

of Soft Engineering Design

This ongoing project is intended to classifythe Hudson River shoreline characteristicsfrom the Tappan Zee Bridge to the TroyDam. The results of this project will be aninventory of shoreline types for the entireestuary. Information obtained from the riversurveys were used to choose five shorelinesites for examples

Initial Shoreline River Survey

River surveys of the estuary shoreline wereconducted to qualitatively assess the currenttypes, condition of natural and engineeredshoreline habitats between Piermont Marshand Troy Dam. The shoreline types wereidentified and classified as part of anongoing separate NYSDEC shorelinecharacterization project that will be used inrestoration planning and prioritization. Theshoreline characterization project wasconsidered to be highly valuable for the

shoreline restoration project presented inthis report.

The initial shoreline classification riversurveys were conducted on August 16thand17th, 2005. The survey team was deployedfrom Norrie Point State Park in Staatsburg,NY in a 21 ft Boston Whaler. On August16th, the river survey team traveled upstreamfrom Norrie Point to Troy Dam and thenback to Norrie Point. On August 17

ththe

team traveled from Norrie Point downstream

to the Tappan Zee Bridge and back. Thesetwo trips provided a visual survey of theentire Hudson River Estuary shorelinetargeted for restoration analysis.

Selection of Restoration Sites for

Preliminary Soft Engineering

Designs

The initial shoreline river survey was used

to prepare a list of candidate sites to beconsidered for a detailed evaluation ofalternative shoreline protection measures.Information from United States GeologicalSurvey (USGS) quadrangle maps,orthographic photos and navigation chartswere also used to develop the list ofpotential restoration sites. A total of 11potential sites were identified and are listedbelow:

1.

Nyack Beach State Park, Nyack. Beach

and park. Masonry wall eroding andscoured.

Nyack Beach State Park Aerial Photograph

Nyack Beach State Park Shoreline

Shoreline


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2. Bowline Point Park, Haverstraw.Eroding shoreline of concrete and riprap.

Bowline Park Aerial Photograph

Bowline Point Park Shoreline

3. Newburgh, possible industrial site

Newburgh Aerial Photograph

Newburgh Shoreline

4. Beacon, possible industrial site

Beacon Aerial Photograph

5. Poughkeepsie. South of Victor C.Waryas Park near Kaal Rock. Erodingconcrete and riprap shore line.

Poughkeepsie, Aerial Photograph

Shoreline

Shoreline


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Poughkeepsie Shoreline

6. Upper Schodack Island, Castleton on theHudson. East side of river withdegrading timber crib with concrete cap.

Schodack Island Aerial Photograph

Schodack Island, USGS Delmar Quad

7. Henry Hudson Town Park, Bethlehem.River-front park with degrading timbercrib and concrete cap.

Henry Hudson Park Aerial Photograph

Henry Hudson Park Shoreline


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8. Campbell Island, Castleton on theHudson. East side of river withdegrading timber crib with concrete cap.

Campbell Island Aerial Photograph

Campbell Island Shoreline

9. Across river from Patroon Island on eastside of river. Timb

HUDSON RIVER SHORELINE RESTORATION ALTERNATIVES ANALYSIS

Documents

river in1609

whenhenry hudson

alden researchlaboratory

usethe estuary

department of commerce

alden research laboratory

hudsonriver estuary

new islands