129 - Using Repeat Lidar to Identify Streambank Erosion Hotspots in Raleigh, North Carolina

Streambank erosion is common in urban watersheds. Water resource managers stabilize streams that are experiencing excessive erosion to improve downstream water-quality, preserve habitat, and protect infrastructure assets. To guide effective mitigation efforts, a comprehensive approach to identify streambank erosion hotspots is needed. Current approaches, such as stream walks or citizen complaints, can be inefficient, inconsistent, and expensive. New tools are needed to remotely identify streambank erosion hotspots. The U.S. Geological Survey and the City of Raleigh, NC have partnered to test new methods to identify streambank erosion hotspots throughout the City’s municipal stream network. Digital elevation models (DEMs) were developed from aerial lidar surveys conducted in 2015 and 2022. Stream channels were delineated from the DEMs and refined using stormwater infrastructure data (pipes, culverts, etc.) provided by the City. High-resolution topographic metrics, such as positive landscape openness and DEM differences, were then determined for the stream reaches throughout the City’s stream network. Rapid field assessments were conducted at 124 reaches to estimate streambank stability and these results were compared to the lidar-derived topographic metrics. Empirical models were developed using watershed attributes (dominant soil class, percent imperviousness, etc.) and stream reach attributes (positive landscape openness, DEM differences, etc.) to predict observed conditions at the 124 field reaches. In this presentation, we share the lidar-derived datasets and watershed attributes that may have the most opportunity for improving streambank erosion detection and prediction. The findings from this study will help the City of Raleigh prioritize stream reaches for future stabilization or restoration efforts.