1. Denise Reed Pontchartrain Institute University of New Orleans

2. Projected Coastal Louisiana Trends: 1956-2050
Land Loss
Projected Land Loss
Land Gain
Projected Land Gain
Land
Water
1956 – sq. mi. of coastal landscape lost
average rate 35 sq.mi./yr. for 44 years
2000 – 2050 Projected loss - another 513 square miles

3. The Past

4. Natural cycles 20th century Time Land Area Delta building
- River deposition
Delta loss
- subsidence, storms
Rapid land loss
Land Area
Limited land
building
Time

5. + = Higher relative water levels Natural Subsidence
Sea-Level Rise
Natural
Subsidence +
= Higher relative water levels
Existing marshes must build up to survive

6. Can marshes keep pace with subsidence and sea-level rise?

7. Marsh Building Processes
DeLaune et al. 1990

8. How do marshes build without sediments from the river?
Storms!
Increase water levels and mobilize sediment

9. Cahoon et al., 1995

10. Hurricane Dolly 22 August 1996
Fourchon
0.2
0.4
0.6
0.8
(m above local datum)
Tide
Sediment Deposition
(g/cm2/day)
0.0006
0.0004
0.0002
5/7/96
5/21/96
6/4/96
6/18/96
7/2/96
7/16/96
7/30/96
8/13/96
8/27/96
Hurricane Dolly 22 August 1996
Date

11. Hurricane Lilli 2002
Reed et al., 2006

12. How Much Sediment for Maintenance?
Katrina and Rita estimated to have delivered 130 million tonnes (Turner et al., 2006)

13. River levees stop restrict delta building to a few areas
Regular sediment supply from the river to
existing marshes is eliminated. Storm
reworking is their only source of sediment.
River levees stop restrict delta
building to a few areas

14. “MRGO”
Houma Navigation
Channel
Navigation Channels

15. Pipeline Canals

16. Solutions?
Maintain what we have
Rebuild what we’ve lost

17. Continuing Current Management

18. Achieving Sustainability

19. “Prevent loss of sediments
into the deep Gulf”

20. Coast 2050

21. “..large-scale concepts that
could provide significant
long-term ecosystem
restoration benefits”

22. Average annual loss to Gulf ~120 million tons of sediment
Photo taken by NASA April 29, 2008

23. 21st Century Sea level rise accelerates…. Storm impacts increase….
Using the River gives Coastal Louisiana a fighting chance