USING A YUNEEC © TYPHOON H HEXACOPTER IMAGING PLATFORM TO ANALYZE SHORT AND LONG-TERM EFFECTS OF EROSION PREVENTION STRUCTURES ON THE RIO GRANDE IN THE SAN LUIS VALLEY, COLORADO

Research to determine short-term effects of erosion prevention structures and possible long-term effects was conducted along a 0.88 mile stretch of the Rio Grande adjacent to the city of Alamosa, CO. Between 2007 and 2011 erosion control structure were installed along river cut banks to help stabilize and prevent further river channel movement. Erosion control structure design intent is to reduce or eliminate erosion. River channel movement is of high interest due to long lasting results of water and sediment fluctuation near cities.

A drone was flown in April, May, and July of 2017. Images were captured at 400 and 500 feet using a CGO3+ camera with 12.4 megapixels and 14 mm lens. Images collected with the UAV drone were georeferenced using ESRI GIS software. Google Earth historical imagery of the same area for previous years was used for comparison. River edges were digitized and mosaiced using ERDAS Imagine.

Images from May and April showed erosion and deposition occurring in areas outside cutbank and point bar designations. There is little previous research that correlates irregular erosion and deposition with erosion prevention structure locations. However based on this study and no known previous evidence, the observed irregular deposition and erosional features have been classified as short-term indirect effects of the erosion prevention structures. Photo comparisons suggest the river has become more narrow and less meandering since 2007.

Drone-based aerial imaging is crucial in capturing seasonal changes and observing river changes due to erosional structures placement. Additional river change observations through the winter and in following years is necessary to further document and understand erosion prevention structure effects and processes.