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Local Applications of Fluvial Geomorphology
Dietz, Amy
Dietz, Amy
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Abstract
This study proposed a method for developing regional curves based solely on hydraulic modeling. Regional curves relate bankfull channel geometry and discharge to drainage area and are typically used to design channel reaches in natural stream systems at locations where stream modifications are required. Such modifications may result from the following projects - highway improvement, bank stabilization, flood control, etc. There are simply situations where modifications must be made to reaches of natural streams in order to accommodate improved drainage structures or to address flooding, scour or erosion problems.
Tributaries of the Marais des Cygne River in Johnson County, KS were used for this study. The watershed for the region studied is predominantly rural and, thus, has many natural reaches. Moreover, detailed terrain data was available for the portion of the Marais des Cygne River considered in this study – with 1-ft contour interval data along the stream corridors. HEC-RAS modeling was used at eight sites or stream reaches within the area studied. Each of the eight stream reaches were judged to be natural based of aerial photography. A HEC-RAS model was developed for each site at a riffle location. Each model used the downstream normal depth boundary condition and contained from 4 to 9 cross sections developed using HEC GeoRAS. The bankfull elevation was estimated for every cross section based on the elevation where the flow appeared from the cross section plot to spill out into one or both of the overbanks.
Trial and error was used for each model to determine the discharge (bankfull flow) that produced the minimum sum of squares of the differences between the computed water surface elevation and the assumed bankfull elevation for all modeled cross sections. The bankfull flow channel geometry parameters were then determined for each cross section and average values were related to drainage basin area via regional curves. The drainage basin areas used were from the recent Johnson County flood study of the Marais des Cygne River.
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Date
2009-10
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University of Kansas Center for Research, Inc.
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Dietz, A, "Local Applications of Fluvial Geomorphology," M.S. Special Project Report, Advisor, A. David Parr, November 2009, 69 pg.