September 8, 2016 Southern Eden Landing … · • MIKE21 Flexible Mesh Combined LiDAR & Bathymetry ... Variable Time Step: • Max: 60 sec • Computed Avg.: 0.25 sec . 7 Tide Gates

September 8, 2016 Southern Eden Landing Hydrodynamic Modeling

Agenda 1. Project Background 2. Modeling Overview

a. Purpose b. Input Parameters c. Layout Configurations

3. Modeling Results a. Restoration b. Flood

2

Southern Eden Landing

Alternatives Analysis

Conceptual Design 2016

EIS/R 2017

30-60% Design

Construction by Design-

Builder

Hydrodynamic Modeling

Cris Benton

Project Background

3

Project Goals: 1. Habitat restoration 2. Maintain or improve

existing flood protection

3. Provide public access and recreation

Project Background

4

Modeling Overview

5

Modeling Overview Purpose

Modeling Purpose: • Determine levee improvement heights • Size and locate:

- Levee breaches - Channels - Water control structures

• From these, locate public trails Pre-design Process: • Historical slough network • Breach sizes

– Empirical geometries of SF Bay historic marshes

– Short-term & long-term tidal prisms

6

Historical Slough Network

Modeling Overview Input Parameters

Model: • MIKE21 Flexible Mesh Combined LiDAR & Bathymetry • Ponds between MSL & MHW Triangular Mesh Elements: • 10 m2 - Narrow levee crests • 200 m2 - Southern ponds • 1,250 m2 - Large flat ponds • 5,000 m2 - Bay Connected Element Paths: • Levee crests and channels

Variable Time Step: • Max: 60 sec • Computed Avg.: 0.25 sec

7

Tide Gates

Railroad Bridge

Modeling Overview Input Parameters

8

Restoration • Maximize tidal prism for

habitat enhancement

• Typical Tide (3-4 weeks)

-4

1

6

5/4/15 5/14/15 5/24/15

Elev

atio

n, F

t N

AVD

88

• Existing Conditions (Alt. A) • Tidal Restoration (Alt. B) • Tidal Restoration & Managed Ponds (Alt. C)

Flood Control • Maintain or minimize max.

water surface elevations

• 100-year tide with 10-year riverine discharge

• 10-year tide with 100-year riverine discharge

Objectives: Hydrologic Scenarios: Layout Configurations:

Modeling Overview Layout Configurations

9

Tidal Restoration (Alt. B)

Modeling Overview Layout Configurations

10

Tidal Restoration & Managed Ponds (Alt. C )

Restoration Results

11

Restoration Results Tidal Restoration (Alt. B)

Objective: • Maximize tidal prism for habitat

enhancement Tidal Propagation Results: • Optimized breach & channel size • Tidal exchange sufficient with

connections to Old Alameda Creek

12

Most Flooded

Least Flooded

Restoration Results

13

Bay & Inland Ponds

C-Ponds

• Old Alameda Creek restricts flow; may erode in future

• C-Ponds will become less muted with additional water control structures

Flood Results

14

EL 10

Flood Results

Effective 2009 (pending update)

15

FEMA FIRM: • Project is within the coastal floodplain • Unaccredited levees • Modeled both Coastal and Riverine

flooding combinations

Hydrologic Scenarios: • 100-year tide with 10-year riverine discharge • 10-year tide with 100-year riverine discharge

ACFCC: Alameda Creek Flood Control Channel OAC: Old Alameda Creek

Coastal Flooding

Riverine Flooding

Coastal Flooding

Riverine Flooding

Flood Results Existing Conditions (Alt. A)

10-yr Tide & 100-yr Discharge 100-yr Tide & 10-yr Discharge

16

9.5 9.5

9.5 8.6 9.8 9.1

9.4 8.4

Maximum Water Surface Elevation Elevations in Feet, NAVD88

Flood Results Tidal Restoration (Alt. B)

10-yr Tide & 100-yr Discharge 100-yr Tide & 10-yr Discharge

17

Maximum Water Surface Elevation Elevations in Feet, NAVD88

-0.8 +0.4

+0.2

-0.5 +0.4

+0.8

Landside Levee Max. WSL : 9.9 feet NAVD88

Flood Results Tidal Restoration & Managed Ponds (Alt. C)

10-yr Tide & 100-yr Discharge 100-yr Tide & 10-yr Discharge

18

Maximum Water Surface Elevation Elevations in Feet, NAVD88

+0.6 +1.2 -2.8

-2.4 -2.4 -2.2

Mid-complex Levee Max. WSL : 10.4 feet NAVD88

Flood Results

19

• Improve levees to 12 feet NAVD88, creating 1.5 to 2.5 feet of freeboard

• Upstream water surface elevations in Creeks maintained or improved

• Flood protection goals were balanced with restoration goals (and recreation)

Example Levee Improvements

Questions?

20