Sponsor
Portland State University. Department of Geography
First Advisor
Teresa L. Bulman
Term of Graduation
Spring 1995
Date of Publication
5-26-1995
Document Type
Thesis
Degree Name
Master of Science (M.S.) in Geography
Department
Geography
Language
English
Subjects
Flood forecasting -- Oregon -- Computer programs, Sandy River Watershed (Or), Clackamas River Watershed (Or), Watersheds -- Oregon -- Computer programs, Regression analysis -- Computer programs
DOI
10.15760/etd.6753
Physical Description
1 online resource (2, v, 130 pages)
Abstract
A geographical information system (GIS) was used to develop a regression model designed to predict flood magnitudes in the Sandy and Clackamas river basins in Oregon. Manual methods of data assembly, input, storage, manipulation and analysis traditionally used to estimate basin characteristics were replaced with automated techniques using GIS-based computer hardware and software components. Separate GIS data layers representing (1) stream gage locations, (2) drainage basin boundaries, (3) hydrography, (4) water bodies, (5) precipitation, (6) landuse/land cover, (7) elevation and (8) soils were created and stored in a GIS data base. Several GIS computer programs were written to automate the spatial analysis process needed in the estimation of basin characteristic values using the various GIS data layers. Twelve basin characteristic data parameters were computed and used as independent variables in the regression model.
Streamflow data from 19 gaged sites in the Sandy and Clackamas basins were used in a log Pearson Type III analysis to define flood magnitudes at 2-, 5-, 10-, 25-, 50- and 100-year recurrence intervals. Flood magnitudes were used as dependent variables and regressed against different sets of basin characteristics (independent variables) to determine the most significant independent variables used to explain peak discharge. Drainage area, average annual precipitation and percent area above 5000 feet proved to be the most significant explanatory variables for defining peak discharge characteristics in the Sandy and Clackamas river basins.
The study demonstrated that a GIS can be successfully applied in the development of basin characteristics for a flood frequency analysis and can achieve the same level of accuracy as manual methods. Use of GIS technology reduced the time and cost associated with manual methods and allowed for more in-depth development and calibration of the regression model. With the development of GIS data layers and the use of GIS-based computer programs to automate the calculation of explanatory variables, regression equations can be developed and applied more quickly and easily. GIS proved to be ideally suited for flood frequency modeling applications by providing advanced computerized techniques for spatial analysis and data base management.
Rights
In Copyright. URI: http://rightsstatements.org/vocab/InC/1.0/ This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).
Persistent Identifier
https://archives.pdx.edu/ds/psu/28416
Recommended Citation
Brownell, Dorie Lynn, "Application of a Geographical Information System to Estimate the Magnitude and Frequency of Floods in the Sandy and Clackamas River Basins, Oregon" (1995). Dissertations and Theses. Paper 4877.
https://doi.org/10.15760/etd.6753
Comments
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