A Dutch Perspective on Coastal Louisiana Flood Risk Reduction and Landscape Stabilization Jos...
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Transcript of 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