| | 1: | | Title: | | | | | Volume/Number: | 2001 | | | | Issuing Agency: | | | | | Description: | A primary concern in the management of the Lower Cache River is the amount of sediment that is deposited in the river's valley in the vicinity of Buttonland Swamp. From previous monitoring studies it is known that floodwaters from Big Creek convey a significant amount of sediment and create a reverse flow condition in the Cache River that carries the sediment into Buttonland Swamp. This study investigated the potential influence of several management alternatives in reducing or eliminating the reverse flow condition in the Cache River, which would alleviate much of the sediment concern. Management alternatives include various options for detention storage in the Big Creek watershed as well as redirecting the lower portion of Big Creek to the west, away from Buttonland Swamp. To evaluate the impact of these alternatives, the hydrology of the Big Creek watershed and its influence on the hydraulics of the Lower Cache River were investigated using two models. The HEC-1 flood hydrology model was used to simulate the rainfall-runoff response of tributaries draining to the Lower Cache River, with emphasis on Big Creek and estimating the impact of detention storage on the Big Creek flood flows. The UNET unsteady flow routing model was then used to evaluate the flow patterns in the Lower Cache River and the impact of management alternatives on flow direction, flood discharge, and stage. Under existing conditions, the UNET model shows that reverse flow occurs in the Lower Cache River east of Big Creek confluence during all the flood events considered. Various detention alternatives in the Big Creek watershed have the potential to reduce the peak of the reverse flow by 26 to 76 percent. Of the detention alternatives examined, the larger detention facilities in the lower reaches of Big Creek appear to produce the greatest reduction in reverse flows. An alternative to divert the lower portion of Big Creek has the potential to totally eliminate reverse flows in the area immediately east of the Big Creek confluence with the Lower Cache River, but may cause increased flooding to the west. To eliminate most of the reverse flow east of Big Creek, and at the same time not increase flood stages farther west on the Lower Cache River, it may be necessary to use a combination of detention storage and either a partial or total diversion of the lower portion of Big Creek. For example, the use of the split flow alternative in combination with the many ponds and Cache valley detention alternatives reduces the peak reverse flows east of Big Creek by 81 percent for a 2-year flood and 92 percent for a 100-year flood. This combined alternative also accomplishes a reduction in the peak stages farther downstream west of Interstate 57 by approximately 0.5 foot. | | | | Date Created: | 9 24 2004 | | | | Agency ID: | CR-2001-06 | | | | ISL ID: | 000000000836 Original UID: 999999994317 FIRST WORD: Hydrology | |
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