GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 259-4
Presentation Time: 9:00 AM-6:30 PM


PARFAIT, Devon N.1, DOWNS, William B.1, COX, Rónadh1, PARFAIT-DARDAR, Shirell2 and CONSTANTINE, José Antonio1, (1)Geosciences Department, Williams College, 947 Main St, Williamstown, MA 01267-2606, (2)Grand Caillou/Dulac Band, Biloxi-Chitimacha-Choctaw, Chauvin, LA 70344

Land loss is a growing threat for all coastal communities, but risks and impacts are unequally distributed. The Biloxi-Chitimacha-Choctaw Confederation of Muskogees is an alliance of three ancestrally related but independent state-recognized tribes that are located in Terrebonne and Lafourche Parishes, marginalized—quite literally—at the southern fringes of Louisiana. Displaced by European settlers, these people have lived in the delta swamplands for generations. Now their homelands are again being taken, this time by land loss. Tribal cemeteries, as well as pre-historic Native American sites and artifacts, are being engulfed as sea level rises and land subsides. Woodlands where adult tribe members ran as children are now replaced by open water. Driveways and yards flood during high tides, even in fair weather. With education levels and median income well below national and state averages, these communities are also at risk socio-economically, with no income safety net to deal with the threat of inundation, or its costs.

Land loss is pervasive in southern Louisiana, but GIS analysis of tribal lands reveals that they are turning to water at rates greater than the average. For example, the area of Terrebonne Parish occupied by the Grand Caillou/Dulac Band of Billoxi-Chitimacha-Choctaw comprises 295 km2. Topographic maps from the 1940s show this area as marshland, drained by numerous bayous, with three distinct lakes (Boudreaux, Gero, and Quitman) By the 1980s, the lakes had expanded and merged to form a single water body; numerous artificial channels (including the 30-mile Houma Navigation Canal) had been dredged; and land loss rates were on the increase. Landsat images spanning 1996 to 2017 show that in 1996 the tribal area was 88% land and 12% water. By 2017 that had changed to 81% land and 19% water. Computed slightly differently, 9% of the 1996 land area had turned to water by 2017. USGS data for the same time period (Couvillon et al. 2017, SIM 3381) show that for Terrebonne Parish as a whole, 3.1% of the land had turned to water; and for the entire coastal Louisiana region, the loss over that time period was 2.8%. Thus the rate of loss of this tribal group's land in the past two decades is about 3 times higher than the background rate. This underscores the extreme vulnerability of indigenous groups in the delta.