Water Resources Research Act Program

Details for Project ID 2009VT44B

Quantifying Sediment Loading due to Stream Bank Erosion in Impaired and Attainment Watersheds in Chittenden County, VT Using Advanced GIS and Remote Sensing Technologies

Institute: Vermont
Year Established: 2009 Start Date: 2009-03-01 End Date: 2011-02-28
Total Federal Funds: $43,204 Total Non-Federal Funds: $115,823

Principal Investigators: Leslie Morrissey, Donna Rizzo, Donald Ross, Eric Young

Project Summary: Stream erosion is one of the most important yet least understood nonpoint sources of sediment and phosphorus (P) threatening the impairment of surface water quality and aquatic habitats within the Lake Champlain basin. High spatial and temporal variability and the difficulties of quantifying erosion rates at watershed scales, however, have severely limited understanding the role and relative contribution of stream bank erosion to water quality degradation. Previous research has not provided the quantitative basis required to weight the importance of stream bank erosion relative to other sediment and P sources at watershed scales or the information needed to address within watershed variability in stream bank erosion over time. To address these issues, we propose to quantify the sediment loads mobilized by stream bank erosion over the past decade (1999-2008) in 15 Chittenden County watersheds by combining very high spatial resolution aerial and satellite imagery, LIDAR-derived elevation data, advanced digital image processing, GIS analyses (e.g. flow accumulation modeling) and field sampling. The proposed research will: 1) develop an automated approach to quantify changes in stream geomorphology over time (e.g. channel migration and bank height), 2) quantify sediment loading to the channel and identify critical source areas that may contribute a disproportionate amount of the total sediment load to streams, 3) address the impact of impervious surface areas on stream stability, and 4) derive remote sensing products indicative of stream stability to complement existing ANR stream geomorphic assessment protocols (e.g. steep banks, change in sinuosity over time, valley and channel slope). Our research will focus on 15 watersheds in Chittenden County, VT of which ten are listed on the state’s 303d list of impaired waters due to urban stormwater or agricultural runoff and six, including an area draining to the non-impaired reaches of the LaPlatte River, are identified as attainment watersheds. The watersheds chosen for study were selected given long-standing focus on sediment, P or fecal contamination within each system, their contribution to water quality in their respective receiving waters (e.g. Shelburne Bay, Burlington Bay, Malletts Bay and the Winooski River), and to represent a variety of anthropogenic and natural stressors over which the extent of stream bank erosion can be evaluated. Verification of specific products, such as areas of active erosion and bank heights used in estimating soil volume loss, will be verified relative to VT ANR Stream Geomorphic Assessment data and targeted field surveys. The proposed effort differs markedly from previous studies in the Lake Champlain basin by taking advantage of watershed-scale synoptic observations over time and detailed elevation measures offered by remote sensing. In addition, our analyses could serve as a baseline against which future estimates of channel stability and erosion could be evaluated and as a means to constrain subsequent sediment and P loading estimates due to stream bank erosion. More importantly, this effort represents not only a significant step towards the development of a systematic approach to quantify sediment loading to the channel due to stream bank erosion throughout the Lake Champlain basin and elsewhere, but also a watershed-scale approach that could greatly aid adaptive management efforts.