Post Katrina Study Assesses New Gulf Coast Region’s Ecological Impacts and Fire Risks

BILOXI, MS (May 30, 2007)—Gulf Coast counties along the path of Hurricane Katrina lost the greatest amount of tree canopy, and suffered the greatest impacts in terms of increased stormwater runoff and poorer air and water quality.

American Forests just completed a 30,000 square mile regional assessment of the impacts Hurricane Katrina had in Louisiana, Mississippi and Alabama by comparing landcover from 2001 and 2006. The findings show that the greatest concentrated loss in tree cover was measured in St. Tammany and Washington Counties in LA and in Hancock, Pearl River, Lamar, Forrest, Stone and Harrison Counties in MS. These counties were directly in the path of the Hurricane. The loss in tree canopy also means a reduction in the environmental benefits that urban forests and other vegetation provides to these communities.

The data compiled in this assessment not only provides the basis for the findings in this report, but is also prepared for on-going use by the cities, counties and states within the study area.

Moderate resolution Landsat satellite imagery and Geographic Information Systems (GIS) software was used to 1) assess the change in landcover pre and post hurricane and the impacts these changes had on air and water and 2) update post-hurricane landcover data used by state forestry agencies for fire management. The study covers 23 counties in Louisiana, 20 counties in Mississippi, and 5 counties in Alabama.

In August of 2005 Hurricane Katrina slammed into the Gulf Coast and changed the physical makeup of tens of thousands of square miles of land.  Along with the human made infrastructure, natural systems such as forests and streams were damaged.  Accounting for the impacts to the natural system in terms of wildfire susceptibility and ecosystem services losses is a necessary part of the recovery process, as is supporting local decision makers with the data and management tools they need to make good decisions about rebuilding the area.  The data will provide local planning agencies with the base maps and technical modeling tools needed to rebuild their communities to take advantage of the ecosystem services that natural systems provide in terms of cleaner air and water and reduced stormwater runoff and erosion.

The data will also be used to update wildfire risk in these predominately rural regions of the country. The updated digital data will be incorporated into a wild land fire risk model (Southern Fire Risk Assessment Software) that will quantify the effects of the storm damage on wildfire risk in the region, pinpointing areas where risk has increased. This will enable the US Forest Service, Southern Group of State Foresters, and state agency fire chiefs to prioritize areas for managing vegetation for fuel reduction.

The most evident changes occurred in the city of Gulfport, MS. The area lost 13% of its tree canopy and gained 12% shrub cover and 4% of its open space in the five year time span. At the same time the area only gained 4% urban (impervious surfaces) area. These changes indicate that hurricane damage rather than development caused the majority of the landcover changes. The city’s 13% percent loss tree canopy increased the need to manage an additional 305,000 cubic feet of stormwater management, valued at $610,500. The loss of canopy also resulted in a 28,000 pounds loss of air pollution removal, valued at $68,000 annually; and a 10,700 ton loss of carbon storage and a 83 pound loss of carbon sequestration annually.

In addition to the regional study, high resolution satellite imagery was analyzed of St. Louis Bay and a portion of Biloxi. “This study provides local leaders and state agencies with the data and software tools they need to rebuild their communities with an understanding of the natural conditions on the land,” explains Gary Moll, senior vice president of the Urban Ecosystem Center at American Forests. “The base maps, wildfire fuel modeling and urban ecosystem analyses will provide the technical capacity needed by local planning agencies for modeling scenarios for land planning.” American Forests will also provide technical assistance and training to agency personnel on the air, and water impacts and benefits produced by natural systems and train them to use software tools for making decisions.

This project was sponsored by the USDA Forest Service. The Analysis was conducted by American Forests and Sanborn.

American Forests emphasizes the important role that green infrastructure plays in air and water quality and stormwater runoff in urban areas. Trees help reduce stormwater runoff by intercepting rainwater, allowing it to evaporate or soak slowly into the ground. Trees absorb air pollutants and their roots filter pollutants from the water.

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