A Comparison of Data Sources for Manual and Automated Hydrographical Network Delineation

Abstract

This study was conducted to evaluate the accuracy of hydrological stream networks derived from two digital elevation models (DEM) and two remote sensing images for a tributary of the Frenchman River in southwest Saskatchewan. This project also provides practical insight into the use of Indian Remote Sensing (IRS) Satellite imaging for hydrological network delineation. IRS images and orthophotographs were used for manual network delineation. Canadian Digital Elevation Data (CDED) and a digital elevation model (DEM) constructed from point and line elevation information from the orthophotographs were used for automated network delineation in program TOPAZ (TOpographic PArameteriZation). Each delineated network was compared with the same National Topographic Series (NTS) blue-line network, as it was assumed the NTS network was the most accurate available representation of the actual drainage network. The networks were compared by visual overlay, Kappa Index of Agreement (KIA) and network statistics such as bifurcation and stream length ratios. The IRS, orthophotograph, and CDED networks were suitable data sources for network delineation, whereas the ortho DEM was not. The major differences between the networks were in the first order streams with consequent effects on higher order streams. First order streams are difficult to delineate in a consistent and accurate manner in a digital environment because of the nature of data sources and differences in the computation processes. As a result, it is concluded that field surveys should be considered in conjunction with digital manipulation for the accurate classification of first order streams.