HYDROLOGIC REGIMES OF TIDAL CHANNEL SALT MARSHES FLOW SYSTEMS, FOURLEAGUE BAY, LOUISIANA, USA

A hydrologic study of a meandering channel and its adjacent marshes on the south-central Louisiana coast (5 Irm from the Gulf of Mexico) has revealed a Bow pattern different from that expected for a natural tid al channel (bayou). A network of constructed channels, ranging in size from the small trapper's channels 1.5 meter wide (called trainasses) to 30 meter wide petroleum-well access canals, has altered the hydrolo gy of the natural bayou and the tidal regime of the adjacent marshes a long the upper reaches of the bayou. Hourly water-level data, recorded at a marsh site in the upper reaches of the bayou, show that the patt ern of marsh inundation is characterized by sporadic flooding interspe rsed by long draining periods. The purpose of this study is to interpr et the different Bow circulation patterns observed in the bayou during two extensive field trips. These trips were in September and October 1991, during which strong continuous north and east winds prevailed Th ose data are augmented by additional data sets taken in May and August 1992 and by other field observations showing the effects of man-made canals which have induced hydrologic changes in the area. These result s indicate that the surface dow patterns in the upper reaches of the b ayou have been decoupled from the lower reaches of the bayou because o f the Bow interception by man-made canals. The upper reaches of the ba you have then been filled in with sediments because of the reduction i n Bow velocity.