a dutch perspective on coastal louisiana flood risk reduction and landscape stabilization jos...

A Dutch Perspective on Coastal Louisiana Flood Risk Reduction and Landscape Stabilization

Jos Dijkman (Deltares / Delft Hydraulics)

Dutch Perspective Project

What it is:• Aimed at long term: 100 years ahead• A reconnaissance level study, based on simple

modeling• Focus on technical aspects• Within framework of LACPR

What it is not:• Design report• Discussed with stakeholders• An alternative for IPET or LACPR

Project Objectives

1. Flood Risk reduction2. Landscape stabilization3. (Enhance the local and regional economy)

1839

Past and Projected Wetland LossPast and Projected Wetland Loss

1870

Past and Projected Wetland LossPast and Projected Wetland Loss

1993

Past and Projected Wetland LossPast and Projected Wetland Loss

wetland loss rate: 1 ha per hour

Past and Projected Wetland LossPast and Projected Wetland Loss

2020

source: USGS

Project Objectives

1. Flood Risk reduction2. Landscape stabilization3. (Enhance the local and regional economy)

• Focus: Metropolitan New Orleans and Mississippi Delta (LACPR planning units 1+2)

Pontchartrain Basin

BaratariaBasin

The NWP Project team

– Rijkswaterstaat– Arcadis– DHV– HKV– TNO– Fugro

– Infram – Geodelft– Royal Haskoning – Alkyon– Delft Hydraulics (project lead)

Comparison Louisiana - Netherlands

System Analysis

challenge goals

Criteria

Design measures

Select promising measures

Strategies and alternatives

visions

evaluation

Preferred Strategy

Scenario’s

challenge goals

Criteria

Design measures

Select promising measures

Strategies and alternatives

visions

evaluation

Preferred Strategy

Scenario’s

• Simplified approach, using realistic data (IPET/LACPR)• Hurricanes only (no river flooding or local rainfall)• Direct damages only (no loss of life or indirect damages)

Risk and Safety

Three ring levee areas:1 East bank NO: central part2 East bank NO: eastern part3 West bank NO

1 2

3

3

Risk and Safety

Optimal safety level: 1/5,000 per year

0,0E+00

2,0E+09

4,0E+09

6,0E+09

8,0E+09

1,0E+10

1,2E+10

1,4E+10

1,6E+10

1,8E+10

10 100 1000 10000 100000 1000000

return period (yr)

Co

sts

(U

S $

)

Investments Risk Total costs

East bank: Central part (ring 1)

Draft IPET results

Sensitivity Analysis

East bank NO Central (1) Optimal safety standard

Base case 1/5000 per year

Flood Damage•50% lower•100% higher

1/1000 per year1/5000 per year

Net discount rate•50% lower•100% higher

1/5000 per year1/5000 per year

Investment costs•50% lower•100% higher

1/5000 per year1/5000 per year

Conclusions Risk and Safety

• Safety level metropolitan New Orleans: 1/1000 per year or better from a cost optimization point of view

• Hardly sensitive for input changes

• Other perspectives (for example loss of life, social disruption, risk averse attitude) may lead to an even better safety standard (1/10,000 or better)

Other topics

• Morphological effects

• Salinity

• Vegetation and levees

Effect of vegetation

2 00 4 0 6 0 8 0 1 0 0 1 2 0 1 6 0 1 8 01 4 0

b a r a t a r i a v e g e t a t e d

p r e s e n t - w i t h v e g e t a t i o n

d i s t a n c e a l o n g c r o s s s e c t i o n ( k m )south north

wat

er le

vel (

m a

bove

MS

L) 8

7

6

5

4

3

2

1

0B aratar ia N ew O r leans

E080

425a

Effect of levees

200 40 60 80 100 120 160 180140

present - vegetation

eco2 - present - vegetation

eco4 - present - vegetation

eco8 - present - vegetation

distance along cross section (km )south north

wat

er le

vel (

m a

bove

MS

L) 8

7

6

5

4

3

2

1

0E080

425b

B aratar ia N ew O r leans

Ridge levee

Alternative Strategies

Open Estuary SystemPassive Surge Reduction

20 B$

Semi-open Defense SystemEnhanced PassiveSurge Reduction

21 B$

ClosedDefense SystemActive Surge Reduction

23 B$

Protected City17 B$

Alternative Strategies

Preferred Strategy

Cost breakdown

Preferred strategy NPV (M$)

Ring levees New Orleans 9,585

Ring levees Plaquemines 1,485

Culverts in existing interstate/railway (5 in total) 68

Fresh water diversions (3 in total) 203

Marshland Stabilization Pontchartrain (750 sq. miles)

3,591

Marshland Stabilization Barataria (600 sq. miles) 2,835

Marshland Creation Pontchartrain (80 sq. miles) 810

Marshland Creation Barataria (60 sq. miles) 608

Marshland Creation Landbridge 675

Total (NPV) 19,860

Management and Maintenance

• Effective institutions required

• Laws and regulations

• Commitment (politics, partners and general public)

• Long term funding (re)construction

• Continued funding for maintenance

Suggestions re. levee construction

1.Levee construction work with locally available materials work with time (soil cement colums) (reduce life

cycle costs) build levees that can safely deal with wave

overtopping

2.Ridge levee

3.Overtopping erosion test (Comcoast project)

Pilot Projects

Canal plugging / filling

Increase effect fresh water diversion

Lake segmentation and land formation

Accelerated natural marshland creation

Fill knowledge gaps and gain experience re. wetland stabilization and creation (“learning by doing”):

Marsh Stabilization measures

Report download

• http://stinet.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA466919

• internet search for: “Dutch Perspective”, Louisiana, DTIC