Coastal and Hydraulics Laboratory

CascadeAn Integrated Coastal Regional Model forDecision Support and Engineering Design

ERDC,Coastal & Hydraulics Lab

Nicholas C. KrausKenneth J. Connell

Coastal and Hydraulics Laboratory

Motivation• Need for predicting response of multiple-system, evolving coastal

regions with interacting projects & coastal processes

• Oceanic and watershed scales involved: sea-level rise, storms, riversediment yields, sediment supply

• Coastal projects influence coast for centuries & on regional scale

• These process scales have not been studied! � Big benefit!

Cascade

Objective

Develop a new class of model, called “Cascade,” for calculating• Longshore sediment transport

• Inlet channel infilling, inlet morphology change, and bypassing

• Multiple projects, regional time and space scales

• Changes barrier islands, inlets, jetties, rivers, washover, wind-blown sand,and processes where data are not readily available

Coastal and Hydraulics Laboratory

Cascade Overview

Simulate longshore and cross-shore sediment transport andlong-term coastal evolution with respect to:

• Complex regional trends• Multiple, interacting projects with cumulative impacts• Inlet sediment storage and transfer• Breaching, washover (storms)• Sources & sinks (beach nourishment, wind-blown sand, rivers)• Jetty construction (impoundment, bypassing)• Navigation channel maintenance• Large-scale gradients in forcing

Coastal and Hydraulics Laboratory

EvaluationFormulation Application

1. Processidentification

2. Equationselection

3. Numericaltechniqueselection

1. Baseline conditions2. Calibration3. Validation4. Sensitivity analysis5. Uncertainty estimate

1. Analysis2. Prediction3. Design4. O&M5. ”What if?”

Cascade Model Details

Coastal and Hydraulics Laboratory

Main Land

flood shoal

flood shoal

ebb shoal

ebb shoal

groin field

regionalshorelinetrend

Erosion

wind-blown

sand; washoverQB

QBR

QBL

QBR

QBL

Offshore regional contour

VE

VF

VE

VF

localshorelineshape

wetland

Nav. channel

Cascade: Schematic of Coverage

bypassing

breach

salinity change

Coastal and Hydraulics Laboratory

Q = longshore sed. transport rateε = efficiency factorF = wave energy flux towards shoreV = mean longshore currentw = sediment fall speed

0.77 fc Kε=

Longshore Sediment Transport RateNew, General Meso-scale Theory

( )(1 )s

Q FVa gw

ε=ρ −ρ −

Coastal and Hydraulics Laboratory

Cascade Sensitivity Analysis

Idealized case:

• Three barrier islands

• Two inlets

• Constant waveheight and angle

• Straight regionalshoreline trend

Test to examine wave& shoreline angle withevolving shoreline

Inlet 1 Inlet 2

Coastal and Hydraulics Laboratory

Idealized case:

• Three barrier islands

• Two inlets

• Constant waveheight and angle

• Curved regionalshoreline trend

Test to examine wave& shoreline angle withevolving shoreline

Inlet 1 Inlet 2

Cascade Sensitivity Analysis

Coastal and Hydraulics Laboratory

Test SitesCascade Development and Validation

Present applications

• South Shore of Long Island (Montauk Point toFire Island Inlet), NY (~ 80 miles)

• Ocean City Inlet with Fenwick and AssateagueIsland (Cape Henlopen to Chincoteague),Delmarva Peninsula (~ 75 miles)

Future applications

Searching for leveraging partners

Coastal and Hydraulics Laboratory

Long Island, NY

ShinnecockMoriches

Fire Island

Coastal and Hydraulics Laboratory

0 20 40 60 80 100 120 140Distance West from Montauk Point (km)

-100000

0

100000

200000

300000

Mea

n Lo

ngsh

ore

Tran

spor

t (m

**3/

year

)

ShinnecockInlet

MorichesInlet

Fire IslandInlet

Land

Atlantic Ocean

Data fromRosati et al. (1999)

Cascade-Calculated Regional Net LongshoreSediment Transport Along South Shore of LI

Coastal and Hydraulics Laboratory

20 40 60 80 100 120 140 160Distance West from Montauk Point (km)

3200

3600

4000

4400

4800

5200

Shor

elin

e Po

sitio

n (m

)

meas. 1983

initial 1931

calc. 1983

Shinnecock Inlet

Moriches Inlet

Simulation of Shoreline Evolution atLong Island, 1931-1983 (detail)

Coastal and Hydraulics Laboratory

1930 1940 1950 1960 1970 1980 1990 2000Time (year)

0

2

4

6

8

Shoa

l Vol

ume

(mill

. m^3

)

Ebb Shoal Complex

calc. Shinnecock

calc. Moriches

meas. Shinnecock

meas. Moriches

Time Evolution of the Ebb Shoal Complexat Shinnecock and Moriches Inlets

Coastal and Hydraulics Laboratory

Simulation of Ebb Shoal Dredging,Shinnecock Inlet-Recovery of Shoal

1930 1940 1950 1960 1970 1980 1990Time, years

0.0

0.5

1.0

1.5

2.0

2.5

Shoa

lVol

ume

(mill

. m3̂)

Ebb Shoal, Shinnecock

Dredging

Natural shoal

1M m3

dredged1M m3

dredged

Coastal and Hydraulics Laboratory

Delmarva Case Study

Large-Scale Topography of the Study Area

Coastal and Hydraulics Laboratory

Shoreline 1980

Net transport

Cape Henlopen Chincoteague

Ocean CityInlet

Indian RiverInlet

0 20 40 60 80 100

Distance South of Cape Henlopen (km)

0

10

20

30

40

Shor

elin

eP

ositi

on(k

m)

-500000

-300000

-100000

100000

Ann

ualN

etLo

ngsh

ore

Tran

spor

t(m

**3/

yr)

Calculated Net Annual Longshore SedimentTransport Along Delmarva Peninsula

Reversal in Transport

Coastal and Hydraulics Laboratory

Coastal and Hydraulics Laboratory

Coastal and Hydraulics Laboratory

Cascade SMS Interface asTechnology-Transfer Delivery Mechanism

DelmarvaPeninsula

Coastal and Hydraulics Laboratory

Cascade SMS Interface

DelmarvaPeninsula

Coastal and Hydraulics Laboratory

Cascade SMS Interface

Coastal and Hydraulics Laboratory

Cascade SMS Interface

Coastal and Hydraulics Laboratory

Cascade SMS Interface

Coastal and Hydraulics Laboratory

Cascade Applicability

• Coastal inlet maintenance

• Channel management

• Inlet and structure bypassing plans

• Fate of beach fill

• Beach fill project planning

• Storm erosion hazard management

• Overwash & breach susceptibility

• Unifying technology for multiple projects (RSM)

Coastal and Hydraulics Laboratory

Cascade: Conclusions

1. Sediment transport & coastal evolution occur at many differentscales with implications for modeling

2. Engineering projects require considerations at regional scale, �dictating need for modeling processes & controls at this scale

3. Cascade can simulate coastal evolution within complex regionaltrends, including inlet sediment storage & transfer, engineeringactivities, & structures

4. Cascade SMS interface provides turn-key system to supportpracticing engineers & scientists in efficiently solving coastalwatershed problems

Coastal and Hydraulics Laboratory

Cascade: Current & Future Developments

• Improved ebb & flood shoal bypassing-Integrated reservoir model (Kraus 2000)

• Spit evolution

• Automated breach opening & closure

• Improved dune & cliff dynamics

based on driving forces

• Further applied testing

�Partnerships welcome!