TERRESTRIAL PHOTOGRAMMETRY USING CONSUMER-GRADE CAMERAS TO STUDY SHORT-TERM TEMPORAL CHANGE: UNCOMPAHGRE RIVER, CO, USA

Aerial photography and photogrammetry have long been used to provide a wide range of topographical data in geomorphology. Unfortunately, because obtaining such data has been expensive, geomorphology studies have been forced to rely on sequences of annually or seasonally produced aerial photographs with long temporal intervals. Regrettably, the long temporal intervals in these studies do not provide the temporal-change accuracy needed to model small-scale movements over short timeframes. The joint improvements of recent photogrammetric software and consumer-grade digital SLR cameras facilitate the development of high accuracy models, which allow small-scale, short-term interval measurements to be achieved. These technological advances make terrestrial photogrammetry both an affordable and effective method to evaluate large and small landscapes.

We have developed a methodology to use terrestrial-repeat and time-lapse photography to produce a high-resolution interval series of digital photographs of short-term changes along the Uncompahgre River. The Uncompahgre River is ~125 km long and flows from Lake Como through Ouray, Ridgway and Delta, CO, to the Gunnison River. The river flows within an outwash valley between Ouray and Ridgway and varies from meandering to braided. Spring melt and convective, summer cloudbursts produce discharges sufficient to result in rapid bank erosion and deposition. To study these short-term changes, we surveyed the river to identify locations where past or potential change occurs. We then produced detailed cross-sections to establish a baseline for change comparison. Cameras stations were installed at multiple locations where images were taken on a daily interval which allowed capture of discharge events. The individual images were processed using photogrammetric software to create a temporal and spatial framework of change along the course of the river. Preliminary results indicate dynamic change along the braided course of the river and slower change associated with meanders.