Texas A&M University Department of Civil Engineering Instructor: Dr. Francisco Olivera CVEN689 Applications of GIS to Civil Engineering Determination of Urban Runoff Using ILLUDAS and GIS Tae Jin Kim 03. May. 2004 Abstract The flowing water function of surface area has been reduced rapidly by lasting progress of urbanization and industrialization. As the sewer pipes of urban area are established or extended, surface area and water route in urban river are mostly paved or connected to sewage box. Also, the peak discharge in urban area is increased due to the runoff enlargement and the watershed lag time reduction. Moreover, by the large-scale residential land development of lower reaches section of a river in urban area, the hydrologic phenomenons are changed and the flood damages in urban area are occurred frequently. In particular, because the damage cost and damage scale is increased relatively due to development rate and population concentration, it is required the accurate and rapid runoff analysis in urban area. Accordingly, in this study, we use Geographic Information System (GIS) and Illinois Urban Drainage Area Simulator (ILLUDAS) to get the urban runoff. The GIS can be used to select the available data according to need. The ILLUDAS can estimate the urban runoff more accurate than the existing methods. INTRODUCTION The flowing water function of surface area has been reduced rapidly by lasting progress of urbanization and industrialization. As the sewer pipes of urban area are established or extended, surface area and water route in urban river are mostly paved or connected to sewage box. Also, the peak discharge in urban area is increased due to the runoff enlargement and the watershed lag time reduction. Moreover, by the large-scale residential land development of lower reaches section of a river in urban area, the hydrologic phenomenons are changed and the flood damages in urban area are occurred frequently. In particular, because the damage cost and damage scale is increased relatively due to development rate and population concentration, it is required the accurate and rapid runoff analysis in urban area. A methodology of adjusting measured annual maximum discharge is presented [R. Edward Beighley, 2003]. The principles of integrated catchment management in south Africa is tested [A.M.W. Grobicki, 2001]. The spatially continuous data in the Reynolds Creek Experimental Watershed is provided [M. Seyfried, 2001]. The Hydrological Land Use Change (HYLUC) model is developed [Ian R. Calder, 2003]. There are many methods to calculate the runoff in urban area. Also, many people try to get the spatial data. Accordingly, runoff through storm sewer pipe in college station is calculated using GIS and ILLUDAS,. METHODOLOGY To calculate the runoff in college station, we use three programs: AUTO-Computer Aid (CAD), Arc Geographic Information System (GIS), and Illinois Urban Drainage Area Simulator (ILLUDAS), as shown in Figure 1. The figure 1 demonstrates the procedures to calculate the urban runoff in college station.Runoff Computation in Urban areaArc-GISAuto-CAD ILLUDASElevation ArcMap PrePro2004ArcToolbox Runoff CalculationSpatial AnalystOther functionsGeoprocessingEditorExport or Import dataMap projectionsWatershed delineationFigure 1 Flow chart for calculating runoff in urban sewer pipe network Among these programs, at this time, I introduce only ILLUDAS. The ILLUDAS is an Illinois Urban Drainage Area Simulator. Its program can calculate runoff, peak discharge, and flow carrying capacity in urban sewer pipe network or design the sewer pipe diameter depending on the discharge in sewer pipe. This program is a Modified British Road Research Laboratory (BRRL) Model. The BRRL model can consider only the directly connected impervious area. To overcome the defects of the BRRL model, ILLUDAS consider the directly connected impervious area and grassed area. As shown in figure 2, ILLUDAS consists of four input data format: Basin parameter, Rainfall parameter, Sewer pipe data, and sub-basin data. Among these data, I use ArcGIS to get the total area, soil type, slope, pipe type, diameter, sub-basin area, surface slope and Impervious & Grassed area. Table 1 shows the detail information of ILLUDAS ILLUDAS INPUTBasin parameter Rainfall parameter Sewer pipe data Sub-basin dataTotal areaSoil typeManning'scoefficientRainfall durationReturn periodTotal rainfalland so onand so onSide slopeSlopePipe typeDiameterAreaLogest pipe lineSurface slope Soil typeand so on Figure 2 ILLUDAS Input FormatTable 1 ILLUDAS Input data Basic parameter Rainfall data Sewer pipe data Sub basin data Total area Rainfall Branch number Branch number Initial abstraction of paved area Rain in time interval Strom sewer section number Storm sewer section number Initial abstraction of grassed area Number of rainfall time interval End branch Sub basin total area Soil kind Delta t(min) Continuing branch Direct paved area minimum diameter in design Standard distribution Option Direct paved area rate Manning Roughness coefficient Duration Reach Indirect paved area Return period Slope Indirect paved area rate Total rainfall Manning Roughness coefficient Inlet time in paved area AMC Pipe shape Inlet time in paved area rate Diameter Longest pipe line Height of pipe Surface slope in paved area Width of pipe Grassed-area related to runoff Side slope Grassed-area related to runoff rate Allowance discharge Inlet time in Grassed-are Rainfall rate Pipe length in Grassed-area Allowance storage Surface slope in grassed-area Test end Hydrologic soil group Hydrograph print out APPLICATION The study area is a college station in Texas. The number of sewer pipe line and sewer pipe manhole in college station is 4624 and 4619, respectively. The study area is 40.6828 square mile [City of College station, 2002]. The calculation of runoff consists of five steps: Step1: Get the elevation data of college station using AUTO-CAD I use AUTOCAD to get the elevation data from contour map n college station. The result is exported to the ArcGIS as shown in figure 3. Figure 3 Elevation data in college stationStep2: Get the raster data of the college station using Arc-GIS To get the various data about the study area, it is necessary to get the raster data in college station. The procedure consist