Channel degradation in southeastern Nebraska Rivers
By: Kenneth L. Wahl and Linda S. Weiss
Edited by: Ward Rim J.
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Abstract
Many stream channels in southeastern Nebraska were dredged and straightened during 1904-15. The resulting channels were both shorter and steeper than the original channels. Tests for time trends were conducted using the nonparametric Kendall tau test to see if the channels have responded to these changes. Tests were conducted on the stages associated with specific discharges and on measurement characteristics at gaging stations. Tests also were conducted on hydrologic forcing variables (annual mean precipitation, annual peak discharges, annual mean discharge, and annual mean base flows). The null hypothesis (that the data were free from trend) was rejected for stages associated with the mean of the annual discharges for 6 of 7 gaging stations in the study area, but was accepted for all 3 gages on the main stem of the Missouri River. The trends at the 6 streamflow gaging stations were for decreasing stages (degrading channels) for specific discharges. The rates of change ranged from about 0.2 to 0.5 m per decade. Mean stream bed elevations computed for individual discharge measurements at these streamflow gaging stations confirmed that the channels are degrading. However, neither the precipitation nor flow variables show evidence of trends. The tendency for the channels to degrade thus cannot be attributed to changes in runoff characteristics and are assumed to be a response to the channel modifications in the early 1900's. Indications are that the channels presently are continuing to degrade.
Suggested Citation
Wahl, K.L., Weiss, L.S., 1995, Channel degradation in southeastern Nebraska Rivers, in Watershed Management Symposium - Proceedings, San Antonio, TX, USA, 14 August 1995 through 16 August 1995, p. 250-259.
| Publication type | Conference Paper |
|---|---|
| Publication Subtype | Conference Paper |
| Title | Channel degradation in southeastern Nebraska Rivers |
| Year Published | 1995 |
| Language | English |
| Publisher | ASCE |
| Publisher location | New York, NY, United States |
| Larger Work Title | Watershed Management Symposium - Proceedings |
| First page | 250 |
| Last page | 259 |
| Conference Title | Proceedings of the 1995 Watershed Management Symposium |
| Conference Location | San Antonio, TX, USA |
| Conference Date | 14 August 1995 through 16 August 1995 |