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Track: Water Resources
Nurunnisa Usul
Middle East Technical University
Water Resources Laboratory
Inonu Bulv
Ankara,
TURKEY
Telephone: 011-312-210-5448
Fax: 011-90-312-210 1262
E-mail: nurusul@rorqual.cc.metu.edu.tr
Okan Kupcu
Using GIS in Obtaining Basin Hydrologic Parameters to Use in SCS Synthetic Unit Hydrograph Method
Defining Issue: Determination of the unit hydrograph (UH) of a basin is very important for the design of hydraulic structures, because unit hydrograph gives information about some parameters of a runoff such as peak discharge, time of the peak discharge, and duration of excess runoff. For gauged basins UHs can be derived from observed data, but for ungauged basins, some synthetic methods are used to determine the UHs. GIS Solution: SCS Synthetic Unit Hydrograph technique is a methodology for determining synthetic UH. This technique needs some parameters and analysis related mainly to the geography and geology of the study area. These are supplied by GIS and then the technique is applied. Methodology: Elevation lines, boundary, soil type, land use and stream network maps are digitized in different coverages as basemaps. The parameters such as area of the basin, main stream length, and slope are supplied from ArcInfo. The curve numbers (CN), which denote the infiltration capacity for different uses
of land and soil type, are determined. Using overlay analysis a land average CN is found. SCS methodologies are applied and the resulting synthetic UH is compared with observed unit hydrographs. Boundary and stream network delineation of a grid module is tested by comparing them with digitized actual boundary and network. Software: ARCEDIT, ArcView, ARCPLOT, and grid modules of ArcInfo are used throughout the study (with PC and later Windows NT versions).
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