A REMOTE SENSING APPROACH FOR ESTIMATING BANK STRENGTH AND PERCENT VEGETATIVE VOLUME ON TEXAS STREAMBANKS

The total approximate in-stream damage from erosion has been calculated at $5 billion for the United States each year, with a minimum of $15 billion spent on stream restoration within the United States from 1990 to 2005 (Bernhardt et al., 2005). Planting riparian vegetation is one of the techniques used to stabilize streambanks during stream restorations, but few data exist evaluating the quantitative effect of various plant species on bank stabilization. This study aims to clarify the role of vegetation on bank stabilization in Texas streams. This relationship is shown herein by calculating bank strength values using channel geometry equations and USGS stream discharge data, and correlating those values to an estimation of the percentage of the bank area's vegetative volume. Vegetation cover along several streams in Texas was calculated using a bare-earth DEM and a LiDAR point cloud at each USGS stream gauge location using Google Earth Engine®. The bank strength of each stream was calculated along a cross section that intersects the USGS stream gauge. At that location, a buffer was generated around that location to collect the percent volume of vegetation (PVV) on the streambank; vegetation type was separated into 3 categories: low, medium, and high. The buffer’s radius was wide enough to account for the root extent of a live oak, the study region’s tallest tree. Results from this research found that higher concentrations of the “high” vegetation were associated with relatively higher bank strengths in sand, clay or mud streams. Additionally, higher concentrations of low and medium vegetation were found to be associated with relatively lower bank strengths in sand, clay or mud streams. There was no change in bank strength when varying volumes of vegetation were analyzed amongst limestone streams. Additionally, this study represents the first calculated coefficients of critical shear stress that correspond to numerical measurements of high vegetation. Knowing the quantitative impact of vegetation may help stream restoration planners decide on an appropriate vegetation volume needed to stabilize streambanks in Texas. This thesis proposes an innovative means of understanding the important relationship, and the quantitative effect, between different vegetation volumes on streambank strengths