GIS-based statistical and fractal/multifractal analysis of surface stream patterns in the Oak Ridges Moraine

Conventional quantities (stream length, number of streams, bifurcation rati o, density of streams per unit drainage area, elevation difference, slope, and perimeter and area of drainage basins) were extracted for approximately 322 drainage basins from a DEM of the Oak Ridges Moraine area, southern On tario. These values were mapped and analyzed using statistical and multifra ctal approaches and GIS to characterize the stream networks and drainage ba sin systems. Useful measures for characterizing drainage basins in the area included, slope, stream densities, ratio of perimeter and area, and ratio of stream lengths. The distinct patterns identified on the basis of these p arameters and on the combined indexes generated by using multivariate stati stical analysis were compared with other datasets (geology, bedrock topogra phy, and drift thickness). The associations illustrate the relationship bet ween stream patterns and geological and geomorphological factors. The strea m networks in the area as a whole have statistical space-filling properties or are free of geological constraints; however, the variance of individual drainage basins can be characterized by a combined principal component con sisting of several quantities. Geological and hydrological interpretations suggest that geological structures, bedrock topography, drift thickness, li thology and slope of drainage basins are the main geological and geomorphol ogical factors influencing the evolution of streams in the area. The result s obtained on the basis of stream and drainage basin analysis may provide i nformation for an improved understanding of hydrological characteristics in the area. As an example, the drainage basins along the Niagara Escarpment and on the south side of the Oak Ridges Moraine show distinct patterns with relatively high stream densities and steeper slopes, which may be one of t he reasons why these basins have relatively high baseflow compared to basin s elsewhere. In addition, high baseflow may have partly induced a relativel y high stream density. (C) 2001 Elsevier Science Ltd. All rights reserved.