Presentation on theme: "Denise Reed Pontchartrain Institute University of New Orleans."— Presentation transcript:
Denise Reed Pontchartrain Institute University of New Orleans
Projected Coastal Louisiana Trends: Land Water Land Loss Projected Land Loss Land Gain Projected Land Gain – sq. mi. of coastal landscape lost average rate 35 sq.mi./yr. for 44 years 2000 – 2050 Projected loss - another 513 square miles
Land Area Time Natural cycles Rapid land loss Limited land building 20 th century Delta building - River deposition Delta loss - subsidence, storms
Existing marshes must build up to survive Natural Subsidence Sea-Level Rise + = Higher relative water levels
Can marshes keep pace with subsidence and sea-level rise?
Marsh Building Processes DeLaune et al. 1990
How do marshes build without sediments from the river? Storms! Increase water levels and mobilize sediment
Cahoon et al., 1995
Fourchon Date 5/7/96 5/21/96 6/4/96 6/18/96 7/2/96 7/16/96 7/30/968/13/968/27/ Sediment Deposition (g/cm 2 /day) Tide (m above local datum) Hurricane Dolly 22 August 1996
Reed et al., 2006 Hurricane Lilli 2002
How Much Sediment for Maintenance? Katrina and Rita estimated to have delivered 130 million tonnes (Turner et al., 2006)
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.