De-energizing Hurricanes with Cypress/Tupelo Buffers: a Plan to Restore the Repressed Swamps of the Lake Pontchartrain Basin by Using Point and Nonpoint Freshwater Sources.

Gary P. Shaffer, Hassan Mashriqui, and Molly McGraw

Project Overview

The problem is hurricanes and the flood and wind damage that accompanies them; wetlands offer a partial solution.  Wetlands are known to de-energize storms, but not all wetlands are created equal.  In particular, forested wetlands dominated by baldcypress (Taxodium distichum) and water tupelo (Nyssa aquatica) are far less susceptible to storm damage than most other wetland types, such as bottomland hardwood forests and fresh and brackish marshes.  In this study we will

1. follow the production and compositional response of the herbaceous and woody vegetation of the Maurepas swamp to the 2005 hurricanes,
2. determine the relationship between density of canopy trees and frequencies of midstory wind throw,
3. isolate all substantial point and nonpoint sources of potential freshwater input in the northern Pontchartrain Basin and build a geographic information system (GIS) of these sources and the spatial extent of currently repressed swamp (swamp that has converted to marsh or open water) that could be restored by these sources, and
4. model the relationship of area of swamp and energy reduction of storms of varying strength, and compare this with other types of wetlands. 

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   Download Research Highlight for this study More about the Hope Canal Diversion on the EPA's Region 6 website A Whole-System Approach for Restoring the Wetlands of the Western Lake Pontchartrain Basin

Using point and nonpoint sources of fresh water to restore swamp will serve the dual benefits of improved water quality, through denitrification and assimilation, and improved wetland health.    The GIS has been produced in ArcGIS, the same package being used to produce the overall PBRP GIS and all of our data files are Excel-friendly.  Point and non-point sources have been mapped and we are in the process of prioritizing them using proximity to wetlands and area of potential benefit.  Our monitoring efforts in the Maurepas swamp have clearly identified a relationship between basal area of cypress and tupelo canopy tree and wind throw of midstory maple and ash.  We also document a clear trajectory from swamp to marsh and open water over the seven year study and show that the 2005 hurricanes improved marsh production by detrimentally affecting tree production.  Modeling the storm surge reduction capacity of baldcypress – water tupelo swamps will be conducted during year 2 of our project.