Stream Shading Assessment with Airborne Multispectral Videography

Heat is a major pollutant of stream waters on Western rangelands. To comply with the Federal Clean Water Act of 1972, Total Maximum Daily Load (TMDL) allocations for heat or elevated stream temperature are being developed for stream systems throughout the Western states. Monitoring compliance to water quality standards is currently done using ground-based methods which are inadequate for the task. Regulatory decisions are often based on only a few point samples per major tributary. This limited sampling provides very little information about the dynamics of stream temperature and its potential effects on beneficial uses (e.g., cold water biota) throughout a stream system. A remote sensing technique is needed to practically and efficiently provide stream temperature information for entire stream systems. Stream shading by riparian vegetation can strongly influence stream temperature by reducing solar heating. Estimation of stream shading using remotely-sensed parameters such as the canopy structure of riparian vegetation has been suggested as a possible surrogate for direct stream temperature measurement In this study, supervised classification of airborne multispectral videography was evaluated as means of assessing the canopy structure of riparian vegetation within Reynolds Creek Experimental Watershed in southwestern Idaho.