Assessing the Effect of Buffer Regulations on Floodplain Vegetation with Multi-temporal Lidar and Satellite Data

Abstract:

Riparian buffer protections are one of the most widely used regional planning tools to protect water resources and floodplains, beyond the requirements of federal regulations. Yet, buffer policies vary widely in their implementation, with regard to the types of features they target, and the extent of protection. Recent work suggests that these policies may not go far enough to safeguard ecosystem services including water purification, flood retention, and return flows that sustain streamflow during droughts. We use multi-year lidar and satellite imagery to examine changes in the extent, structure, and quality of vegetated buffers fringing riparian areas, wetlands and other water bodies in Eastern North Carolina from 2000-2015. We also evaluate the effect of local buffer protection regulations that became effective between 2000 and 2009. On average, canopy height increased across all river basins, with the greatest gains along low to mid-order streams, decreasing moving downstream; gains were greater closer to features, decreasing with distance. However, in terms of biomass, the greatest increases occurred on lands proximal to low order streams, followed by wetlands, lakes and ponds. On average, canopy height increases adjacent to lower order streams, as well as lakes and ponds, were greater in watersheds with protection policies (0.003 < p < 0.6); yet no significant effect of policy was observed for larger order rivers, wetlands, or reservoirs, as determined by a Kruskal-Wallis test. A Mann-Kendall trend analysis found that buffer greenness significantly increased, yet increases land surface temperature, and drought indicators also increased. Local and regional policies may become even more important for water resource protection given changes to federal clean water act legislation.