Quantifying Sediment and Phosphorous Loading from Streambank Erosion using Terrestrial Laser Scanning to Support Sediment and Nutrient Budgets

Suspended sediment transported through watersheds comes from many sources, streambank erosion being one of the most common non-point sources. As the frequency of precipitation events in the Northeast is expected to increase, the erosional processes in the watershed and along the stream channel are expected to follow suit. Phosphorus and nutrients from various sources bind to the suspended sediment, causing a rise in the concentrations in Vermont waterways and lakes. Therefore, quantifying streambank erosion is a prerequisite to reliably predicting geomorphic channel responses and their impacts on rivers and receiving waters. In this work, we use periodic aerial photography and 3D scans of streambanks, collected using a terrestrial laser scanner, to quantify erosion rates and sediment loadings at select streambank sites in the Mad River watershed in Vermont. Streambank erosion is also estimated from turbidity monitoring on tributaries and the outlet of the Mad River watershed. The streambank erosion measured at monitoring sites is then compared to the estimates from the turbidity monitoring to more reliably quantify loading from streambanks. Total phosphorus (TP) data collected from a variety of sites throughout the region are being used to calibrate simple models to convert sediment loading to TP loading. The sediment and nutrient loading from streambanks is then used to inform conceptual sediment and nutrient budgets for the Mad River watershed.