WIGGINS PASS DELFT3D NUMERICAL MODELING:DELFT3D …

WIGGINS PASS DELFT3D NUMERICAL MODELING:DELFT3D NUMERICAL MODELING:

CALIBRATION & CHANNEL ENHANCEMENT ALTERNATIVESENHANCEMENT ALTERNATIVES

Steve KeehnLindino BenedetLindino BenedetRafael Bonanata

22nd October, 2008

TOPICSTOPICS

• Recap of last meetings• Recap of last meetings

• Field measurements and hydro calibration (recap)

• Morphology calibration (recap)

• Alternatives (optimized 1 yr, 2 yrs, 4 yrs, beach fill)

• Conclusions• Conclusions

• Future directions

INTRODUCTION• Numerical model known as Delft3D

• Waves, Currents, Sediment Transport, Morphology (erosion and sedimentation), D3D is actually 4 models in onemodels in one

• Morphology update in real time

• 1 yr morphology change simulations

• Testing different channel configurations to evaluate channel stability and adjacent shoreline effectseffects

Decision Making in Coastal Engineering

Design

Recap• 1978 USACE study for navigation improvement develop plan to act to improve hazardous navigation conditions of natural i l tinlet

• 1982 CEC study hydraulics and permitting of USACE plan

• 1989 CEC follow up

• 1995 CPE IMP1995 CPE IMP

• 2004 H&M analysis (feasibility study)

• 2007 H&M modeling report

• 2008 CPE modeling & engineering study

Recap – Last Meeting (June 08)• Importance of Sanibel island and its shoals on sheltering Wiggins from waves from northern quadrantgg q

• Net transport direction north of Wiggins Pass is south to north (reversal just around inlet zone to just south of it)

• All channel configurations tested (1970, 2004, 2007 pre and post) showed very shallow depths after 1 yr

• Suggested fill placement closer to inlet and testing different channel layouts and hydraulic connections

Recap – Last Meeting (August 08)• Importance of two sediment fractions in resolving channel and adjacent beaches realisticallyj y

• Importance of swash channel and reversal adjacent to barefoot beach (it is losing sand in both directions)

• Tested 8 different alternatives

M t ff ti lt ti (i t f i l t d th• Most effective alternatives (in terms of inlet depth maintenance and reduction of erosion at barefoot beach) consisted of straight channel with a flood shoal cut and temporary sand dikestemporary sand dikes

• Selected four alternatives for additional simulations (1 yr, 2 yrs 4 yrs hurricane beach fill) – Today’s meetingyrs, 4 yrs, hurricane, beach fill) Today s meeting

Today’s Meeting (Oct 08)• Four alternatives tested: current dredge plan, two straight channel configuratios with hydraulic connections and one re-g yaligned channel

• One year, two years and four years simulations using average wave climate

• One year simulations with beach fill placement

• One year simulation using hurricane wave climate

Wave Data

Wave Data

Wave Data

TransportSW WSW Waves

TransportNWNW waves

TransportNNWNNW waves

Net Transport – 1 yr

Model Grids

Model Setup

• 2D model with depth averaged currents initially

• 3D Sensitivity analysis (10, 6, 5 layers) showed improved results

• Final model run in 3D with 5 vertical layers (each layer 20% of the water column)

• After sampling of the channel decided to add a second sediment fraction (coarser)sediment fraction (coarser)

ADCP Measurements

• Currents (velocity, direction)• WavesWaves• Water level• Temperature

ADCP Measurements

Hydrodynamic Calibration

Waves Calibration

Sand Samples

Morphology – June 2008

Morphology Change Feb-07 to June 2008Feb 07 to June 2008

26,400 cy/yr

Morphology Model – 1 yr

Simulation #37

Morphology Model – 1 yr

28 200 cy/yr28,200 cy/yr

Net Transport – 1 yr

Alternatives

Alt 1. Permitted Channel

Alternatives

Alt 2. straight channel + Flood cut + N-S + Dikes

Alternatives

Alt 3. Permitted Channel + Flood cut + N-S + Dikes

Alternatives

Alt 4. New channel alignment and dimensions

Alternatives

Alternative 1. Currently permitted channel

250 ft wide 13 ft deep250 ft wide, 13 ft deep

Alternative 2. New Straight Channel with Hydraulic Enhancements

Straight channel (200 ft wide, 11 ft deep), flood shoal cut, sand dikes to direct the flow

Alternative 3. Permitted Channel with Hydraulic Enhancements

Permitted outer-channel (250 ft wide, 13 ft deep), flood shoal cut, sand dikes to direct the flow

Alternative 4. New Realigned Channel g

Realigned Channel following natural ebb jet, 200 ft wide, 11 ft deep

Morphology After 1 year

Alt. 1 Permitted Channel Alt. 2 New Straight channelg

Morphology After 2 years


Morphology After 4 years


ONE YEAR SIMULATIONSONE YEAR SIMULATIONS

Alt. 1

Permitted channel

Alt. 2

New Straight Channel + Hydraulic CConnections

Alt. 3

Permitted Channel + Hydraulic CConnections

Alt. 4

Re-aligned Channel

Relative Changes

• The next two slides show the morphology predicted after one yr for the alternative being evaluated subtractedafter one yr for the alternative being evaluated subtracted by the morphology predicted after 1 yr for alternative 1

Th lid h th l ti h th h• The slides show the relative changes, or the changes caused by the alternative evaluated in relation to the current permit plan which is represented by alternative 1

• Shades of green indicate that the alternative tested caused deposition in the site in relation to alternative 1caused deposition in the site in relation to alternative 1 and vice-versa for shades of red

Alt 1 – Permitted ChannelAlt 2 – Straight Channel, Hydraulic Connections - Alt 1 Permitted Channel Hydraulic Connections

Alt 1 – Permitted ChannelAlt 4 – Re-Aligned Channel - Alt 1 Permitted Channel g

Alt 1 – Permitted Channel Alt 2 – Straight Channel + Hydraulic Connections

Comparison of net sediment transport plots for two different alternatives

Alt 1 – Permitted Channel Alt 4 – Re-Aligned Channel

Comparison of net sediment transport plots for two different alternatives

TWO FOUR YEARS SIMULATIONSTWO- FOUR YEARS SIMULATIONS

Morphology PredictionsMorphology Predictions

Alt 1 2 yrs

Alt 2 2 yrs

Alt 1 4

Alt 2 44 yrs 4 yrs

Alt 1 2 yrs

Alt 3 2 yrs

Alt 1 4

Alt 3 44 yrs 4 yrs

Alt 1 2 yrs

Alt 4 2 yrs

Alt 1 4

Alt 4 44 yrs 4 yrs

Erosion Sedimentation PlotsErosion-Sedimentation Plots

Alt 1 – Permitted Channel – 4 yrs Alt 2 – New straight channel – 4 yrs

CAlt 1 – Permitted Channel – 4 yrs Alt 3 – Permitted Channel, Hydraulic Connections – 4 yrs

CAlt 1 – Permitted Channel – 4 yrs Alt 4 – Re-Aligned Channel – 4 yrs

Simulations of Alternative 1 withSimulations of Alternative 1 with the Beach Fill (1 yr)

Alt. 1 + Beach Fill

60,000 cy between R15 and R13

Relative Change (alt 1 with beach fill – alt 1 withoutRelative Change (alt 1 with beach fill – alt 1 without fill) showing fill spreading and little additional sedimentation at inlet due to fill placement

Hurricane (1 yr)Hurricane (1 yr)

Alt 1 Hurricane

Alt 2 Hurricane

Alt 3 H i

Alt 4 H iHurricane Hurricane

Decision MatrixDecision Matrix

V l Ch ( / )

Alt 1 Alt 2 Alt 3 Alt 4 Alt 1 + B h Fill

Volume Changes (cy/year)

Alt 1 Alt 2 Alt 3 Alt 4 Alt 1 + Beach Fill

1 year 28,300 27,000 29,100 38,900 30,100

2 years 22,100 17,000 20,800 23,900

4 years 12,800 8,600 12,800 14,4004 years 12,800 8,600 12,800 14,400

Decision Matrix (1 year)

Outer Channel C t lli

Outer Ch l Ch l

North Sh li

South Sh li Li tAlternative Controlling

depthChannel Infill Rate

Channel Stability

Shoreline (R15-R16)

Shoreline (R17-R18)

Limestone removal

No. Alternative Description

Ft-NAVD CY/yr Description Description Monitoring Survey Feb 2007 to June 2008 4 to 7 26,400

Poor Erosive slightly accretional4 to 7 26,400

Alt 1 Permitted channel4 to 6 28,300

Poor = = No

Alt 2 New Straight channel + hydraulic connections 6 to 8 27,000

Good + = Some

Alt 3 P itt d h l G d NAlt 3 Permitted channel + hydraulic connections 5 to 7 29,100

Good + = No

Alt 4 Re-aligned channel6 to 8 38,900

Intermediate - +/- Yes

Alt 1 + Beach Fill + = No4 to 6 30,100 Poor

No

Decision Matrix (4 years)

Outer Channel C t lli

Outer Ch l Ch l

North Sh li

South Sh li Li tAlternative Controlling

depthChannel Infill Rate

Channel Stability

Shoreline (R15-R16)

Shoreline (R17-R18)

Limestone removal

No. Alternative Description

Ft-NAVD CY/yr Description Description Alt 1 Permitted channel

3 to 5 12 800

Poor Erosional Stable No3 to 5 12,800

Alt 2 New Straight channel + hydraulic connections 4 to 7 8,600

Good Slightaccretion

Stable Some

Alt 3 Permitted channel + hydraulic connections 4 t 7 12 800

Good Slight accretion

Stable Nohydraulic connections 4 to 7 12,800 accretion

Alt 4 Re-aligned channel4 to 7 14,400

Intermediate Highly erosional

Stable Yes

Conclusions• Off all alternatives tested (16 total) the two alternatives where there was a cut in the flood shoal and temporary sand dik i th ld h l th l th t t thdikes in the old channel were the only ones that meet the goals of the project

• Sedimentation rates in the model decrease with time as expected, after 2 yrs a quasi-equilibrium is reached and there is minimal additional sedimentation

• Beach fill placement between R13 and R15 had minimum effects on channel sedimentation and positive effects on barefoot beach and is therefore recommended

• During extreme hurricane years the channel gets filled in to a g y g4 yr ‘normal rate’ no mater what you do (emergency response)

ConclusionsConclusions• To promote stability of barefoot beach and provide improvements to navigation one has to re-align the channelimprovements to navigation one has to re-align the channel and block the 2 channel system (swash channel)

• This can be done by flood shoal dredging to straighten the• This can be done by flood shoal dredging to straighten the tidal jet and temporary sand dikes

• If flood shoal dredging is unacceptable then a similar effect• If flood shoal dredging is unacceptable then a similar effect could be achieved (blockage of swash channel) by use of structures

• If same plan is continued then some relief to barefoot beach can be provided by placing fill between R15 and R13 and

ll dj t t i h l d isome small adjustments in channel design

Future Tasks Recommended

• Refine the best alternative and simulate it for 1 yr, 2 yrs and 4 yrs, with beach fill placement. The final alternative will be a combination of alternatives 2 and 3

• Write final modeling report and provide recommendations for detailed design phase and new permit application

• Refine decision matrix of scenarios for comparison

Results of Preliminary E i t l I ti ti fEnvironmental Investigation of

Wiggins PassWiggins Pass

S kSnookSea grassMangrovesFlood Shoal SubstrateFlood Shoal Substrate

Wiggins Pass Environmental PermittingWiggins Pass Environmental Permitting

Potential Snook Habitat•Common Snook (Centropomus undecimalis)

•Mostly found in mangrove fringed coastal waters of the Atlantic and Gulf of Mexicothe Atlantic and Gulf of Mexico.

•Juveniles use the estuary as developmental habitat.

Ad l i l i f i•Adults congregate to inlet openings for spawning.


FWC Designation: Snookg•Listed as a ‘protected species of concern’ for the purposes of public awareness and commercial p p pfishing, however, that listing does not carry any specific conservation regulations in regard to dredging activitiesdredging activities.

•No critical habitat has been designated for snook, especially not Wiggins Passespecially not Wiggins Pass.

•In the Gulf Region, closed season for snook occur: During the months of Dec., Jan., Feb., May, June, g , , , y, ,July, and Aug.

Wiggins Pass Environmental PermittingPreliminary Substrate Reconnaissance

Main Channel

Flood Shoal

South Channel

•Preliminary visual reconnaissance of the main and south channels

•No seagrass or hardbottom resources found within the main channelg

•South channel mostly silty within the throat, turning courser towards the flood shoal

Wiggins Pass Environmental PermittingMangrove Habitat

Red Mangroves

Red Mangroves


State Regulations: Mangrovesg g•The Mangrove Trimming and Preservation Act (1996); enforced by the Florida Dept. of Environmental Protection( ); y p

•The term ‘trimming’ refers to the cutting of mangrove branches, twigs, limbs, and foliage; ‘altering’ means to remove, defoliate, or destroy mangroves.

•An individual permit must be applied for in order to conduct mangrove alteration or trimming.

•A professional mangrove trimmer must supervise all ti itiactivities.

EasternEastern Edge Fl dFlood Shoal

EasternEastern Edge Fl dFlood Shoal

ChannelChannelInter-sectionsection

Thank YouThank YouThank YouThank You

WIGGINS PASS DELFT3D NUMERICAL MODELING:DELFT3D …

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