Mapping Urban Land Cover Using QuickBird NDVI and GIS Spatial Modeling for Runoff Coefficient Determination

This research presents an integration of remote sensing and GIS for determining the runoff coefficient (C) recommended by the American Society of Civil Engineers and the Water Pollution Control Federation in 1969. The C is a runoff index used as an input parameter in the most commonly used procedure: the rational method for storm-water runoff calculation in small urban watersheds for storm drainage design and analysis. The objective of this study was to evaluate 8-bit and 16-bit QuickBird (QB) NDVI satellite imagery using an unsupervised classification and the ISODATA algorithm to map impervious area and open space used for the determination of C in GIS spatial modeling. The research hypothesis was that mapping impervious area and open space using high spatial resolution NDVI satellite imagery, generated using the ISODATA algorithm, was an efficient and effective information extraction approach for accurately estimating spatial representative C values. The overall classification accuracies of the six QB NDVI thematic maps produced were similar, about 92 percent. In order to assess the utility of high spatial resolution satellite imagery and to validate the composite runoff index geographic model developed by Thanapura in 2005 and 2006, the C values were calculated in GIS spatial modeling and compared to the industry standard C. Finally, the hypothesis was accepted that the finer resolution image and mapping approach used in this study allowed for better discrimination of land-cover and thus a more accurate representative C estimation. Introduction Engineering hydrology is concerned with analyzing and designing hydraulic structures for safe and effective passage of flood flows. Two basic levels of analysis exist. In the first Mapping Urban Land Cover Using QuickBird NDVI and GIS Spatial Modeling for Runoff Coefficient Determination [THIS PAPER WAS THE WINNER OF THE 2006 BAE SYSTEMS AWARD GIVEN AT THE ASPRS 2006 ANNUAL CONFERENCE] Pravara Thanapura, Dennis L. Helder, Suzette Burckhard, Eric Warmath, Mary O’Neill, and Dwight Galster level, a peak flow calculation is used to determine the maximum runoff rate at a given point resulting from a storm event. The designs at this level of analysis are often for storm sewers and culverts whose only function is to convey runoff away from areas where it is unwanted. The second level is more complex. This analysis consists of the generation of a runoff hydrograph throughout a storm to provide information on flow rate versus time and runoff volume. This type of information is essential when drainage basins are too large or too complex to be treated by peak flow estimation methods, or when the analysis of natural or artificial detention or retention facilities is required (Methods and Rocky, 2003). Estimation of peak discharge rates and synthesizing complete discharge hydrographs are, therefore, two of the more challenging aspects of engineering hydrology (Viessman and Lewis, 2003). In small and mid-size urban watersheds, accurate estimation of storm water runoff volumes and peak discharge is critical for the design of minor drainage structures. Examples of minor hydraulic structure types can range from small crossroad culverts, levees, drainage ditches, urban storm drain systems, and airport drainage structures to the spillway appurtenances of small dams (Viessman and Lewis, 2003). Calculating peak discharge composed of surface runoff through a development will allow planners to place appropriately sized culverts, sewer pipes, and storm drains to assure effective storm water flow out of an area. Determining the limits and being too conservative not to spend more money than necessary in design structures can lead to considerable damage such as flooding cellars (Kuichling, 1889). In the United States, many of the farmlands, wetlands, forests, and deserts have been changed into human settlements during the past 100 years (USGS, 1999). Population growth and urban development can create potentially severe problems in urban water management (Chow et al., 1988). Transformation of rural lands into urban increases a watershed’s response to precipitation. Large amounts of pervious land-use have been replaced by impervious land-use, and a network of man-made drainage has altered the natural drainage characteristics. Construction of houses, commercial buildings, parking lots, paved roads, and streets increases the impervious cover in a watershed and thus reduces PHOTOGRAMMETRIC ENGINEER ING & REMOTE SENS ING J a n ua r y 2007 57 Pravara Thanapura and Mary O’Neill are with the Engineering Resource Center, South Dakota State University, Box 2220, Harding Hall, Brookings, SD 57007 (pravara.thanapura @sdstate.edu). Dennis L. Helder is with Electrical Engineering and Computer Science, South Dakota State University, Brookings, SD 57007. Suzette Burckhard is with Civil and Environmental Engineering, South Dakota State University, Brookings, SD 57007. Eric Warmath is with the Department of Transportation, State of Nevada, Carson City, NV 89712. Dwight Galster is with Mathematics and Statistics, South Dakota State University, Brookings, SD 57007. Photogrammetric Engineering & Remote Sensing Vol. 73, No. 1, January 2007, pp. 057–065. 0099-1112/07/7301–0057/$3.00/0 © 2007 American Society for Photogrammetry and Remote Sensing 07-06-061 12/11/06 3:09 PM Page 57