QUANTIFYING MORPHOLOGIC CHANGES IN LOW GRADIENT RIVERS CROSSING THE BATON ROUGE FAULT ZONE

This study investigates the signature of faulting in low gradient, alluvial rivers crossing the Baton Rouge Fault Zone (BRFZ), which encompasses a set of East-West striking normal faults in southeast Louisiana. These faults exhibit subtle surface expressions of a few meters or less, and non-traditional methods are needed to better constrain the history fault motion. One of these methods is quantifying geomorphic changes in the large number of rivers that cross the fault zone. Previous studies have described the theoretical response of alluvial rivers to different tectonic influences, but few studies have explored these relationships in very low-gradient environments.

We hypothesize that faulting will be evident in patterns of river sinuosity, slope, and channel width. Our study is currently focused on the Tickfaw River near Holden, Louisiana, which for this region is representative of a relatively undisturbed low-order river. We are conducting field surveys using a pioneering Differential GPS method, as well as GIS analysis of the LA LiDAR data and flow modeling using the HEC-RAS software program. Historic channel features are being explored through aerial photography dating back to 1954. Preliminary results show relatively low sinuosity values in the region of the river crossing the northern portion of the fault zone contrasting with relatively high sinuosity values in the region of the river crossing southern portion of the fault zone. Our goal is to use geomorphic indicators to identify areas of the fault that are currently active, in order to identify regions that are vulnerable to subsidence.