|Shields Jr, Fletcher|
Submitted to: International Conference on Water Resources Engineering Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/1/1998
Publication Date: N/A
Interpretive Summary: Stream channels have been straightened and enlarged to provide flood control. Sometimes channel straightening is followed by bed lowering due to erosion (channel incision). Many observers have suggested that channelized, incised stream channels deliver larger, briefer storm flows downstream than meandering streams. Few data are available to quantify these effects. A case study was conducted using data from two adjacent watersheds. The channel network in one was channelized, while the other was not. Other aspects of the watersheds were quite similar. Large storms passed through the channelized watershed about 3 to 4 times faster than for the other watershed. Slower, lower high flows in the meandering channel were likely due to frequent overbank flow and storage of floodwaters in the floodplain. Meandering channels offer significant benefits in terms of downstream flood control for landowners and federal agencies charged with duties in this area.
Technical Abstract: Fifty-five years of daily stage records were examined for two gages located on adjacent streams in northwestern Mississippi. The two streams have similar watersheds, but differ in management history: the upstream drainage network for one has been channelized, but the other has not. Stage hydrographs for the two gages are radically different. Initially, large storm-events took nearly three times as long to pass the gage on the sinuous stream as on the channelized stream. After the sinuous stream incised in response to downstream channelization, hydrographs for the two gages became more similar. We conclude that sinuous streams with frequent overbank flow offer significant benefits in terms of downstream flood peak attenuation. Results indicate that channel incision and channelization have similar effects on stage hydrographs.