Subtask 3.5: Spatial Analysis of Mississippi Delta Landscape and Ecosystem Change: 1700s to 2000s

Subtask Leader: Mark Kulp - Pontchartrain Institute for Environmental Sciences (PIES), University of New Orleans

Subtask 3.5 Aim:

Figure 4. Coastal land loss time-series map for the Caminada Quadrangle from the USACE by Britsch and Dunbar (2007a) [enlargement]

The Mississippi River delta plain (MRDP) forms the geomorphic heartland of the Northern Gulf of Mexico (NGOM) study area. Over the last two decades scientists from the U.S. Geological Survey, UNO, and the U.S. Army Corps of Engineers have conducted studies of this changing landscape. The first geomorphic change research documented the loss of land in this delta.

Since 1932 over 1000 square miles of land have been loss. Land was observed to be lost at a rate of 10 square miles a year at the beginning of the 1900s. By the 1970s the land loss rates peaked at 40 square miles per year. Twenty years later the rates of loss deceased to 20 square miles. In 2001 the rate of land loss continues at approximately 20 square miles a year.

In the 1980s the USGS Coastal Marine Geology Program initiated a series of cooperative studies (COOP) investigating the geologic framework and geomorphology of coastal Louisiana. The first USGS COOP focused on the barrier Islands surrounding the Mississippi delta. This USGS COOP produced the landmark Louisiana Barrier Island Atlases by Williams et al, (1992) and List et al, (1994). Subsequent USGS COOPs focused on critical processes of coastal change, west Louisiana , the Ponchartrain Basin, and the impact of hurricanes. During the late 1990s U.S. Geological Survey and University of New Orleans scientists sought to further the understanding of the Mississippi delta land loss crisis from that of direct measurement to a quantification the type and process of land loss. Britsch and Dunbar (1990) published an USACE land loss atlas for the Mississippi delta that mapped approximately 690,000 acres of land loss. Penland et al, (2000a) proposed a geomorphic land loss classification using the Britsch and Dunbar (1990) atlas which divided land loss into two distinct types, shoreline and interior.

Further, Penland et al, (2000b) proposed a process classification which defined 3 distinct process classes of loss, these were erosion, submergence, and direct removal. These new analyses concluded that 30 percent of the land loss in the delta was classified as shoreline loss and the remaining 70 percent was classed as interior loss. In terms of process, oil and gas ranked as

the top cause of Mississippi land loss at 36 percent followed by wave erosion at 26 percent, altered hydrology at 21 percent and the remaining 17 percent of coastal land loss was attributed to 14 other causes. Thus, for the first time through this geospatial analysis approach we were able to fully quantify and interpret the processes of coastal change in the Mississippi delta at a resolution suitable for coastal management, protection and restoration.

The USACE recently issued a new set of coastal land loss maps for the Mississippi delta by Britsch and Dunbar (2007a-e). This map set depicts land loss at 5 time periods: 1932-1956, 1956-1973, 1973 1983, 1983-1990, and 1990-2001 (Figure 4). We propose to use the methodology developed by Penland et al, (2000a and b) to classify the geomorphology and processes of Mississippi delta land loss for these 5 time periods. Clearly, the processes of change are constantly evolving and this unique geospatial dataset by Britsch and Dunbar (2007a-e) will provide an opportunity to quantify the processes of coastal change which is critical to forecasting the vulnerability of coastal Louisiana , Mississippi , and Alabama to future hurricanes, sea-level change and climate change.

To support this detailed time-series analysis of coastal change between 1932 and 2001 we will further investigate the early historic geomorphic history of the NGOM using early the maps and sea charts dating from the Age of Discovery. French, Spanish, Dutch, and British houses of cartography provide tremendous insight into the geomorphology of our coast before the Mississippi River watershed and its delta was so extensively modified by man. In addition, we propose to capture specific GIS layers related ecologic and geomorphologic features that will be pertinent to interpreting the patterns of landscape change we are observing in the Mississippi delta.

Subtask 3.5 Activities:

The primary objective of Subtask 3.5:

is to quantify the geomorphology and processes of coastal change in the Mississippi delta over the last 500 years. Of particular interest is to understand the roles of framework geology, storms, submergence, and man as agents of coastal change.