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|Title:||Investigation of wetlands hydraulic and hydrological processes, model development, and application|
|Authors:||Enserch Environmental Corporation.|
Ray Chapman & Associates.
Wetlands Research Program (U.S.)
Martin, Thomas H.
Chapman, Raymond S.
Davis, Jack E.
|Publisher:||Coastal Engineering Research Center (U.S.)|
Engineer Research and Development Center (U.S.)
Abstract: We investigated hydrologic characteristics of the Cache River wetland between Patterson and Cotton Plant, AR. The Cache River is an underfit stream with wetlands predominantly located in abandoned channels and backswamps. Much of the Cache River upstream of the study area has undergone extensive channelization to allow agricultural development in the basin. Hydrologic measurements included U.S. Geological Survey river gauges at the upstream and downstream limits of the study area (40 river km apart), water level recorders inside the study area, a nest of deep and shallow groundwater wells that monitored variations in the underlying aquifer, a meteorological recording station that collected precipitation, air temperature, and solar radiation data inside the study area, and regional precipitation data. Analysis of the wetland's water budget showed that the system is dominated by river flows and the magnitudes of the other water budget components fall within the error of well maintained river gauges (5 to 10 percent). The system is characterized by the floods occurring from late-fall to late winter and again in mid- to late spring. Peak flood flows are approximately 185 m³/s for a 2-year return event and 270 m³/s for a 5-year event. Peak flows between the upstream and downstream gauges are reduced by 10 to 20 percent with greater attenuation. occurring when the system is initiaJJy drier. Peak flow at the downstream gauge lags the peak at the upstream gauge by 4 to 8 days depending on the antecedent conditions. Flooding of the overbank areas is a result of constrictions in the downstream reaches of the study area. Flood-peak attenuation between the upstream and downstteam gauges is due mainly to floodplain storage with flow resistance contributing minimally. A Wetlands Dynamic Water Budget Model was developed and applied to support the field investigation. The model augmented the field study's measured hydrologic data by filling data gaps that occurred due to gauge problems and by providing simulated data for broad areas of the wetland, particularly those far away from any measurement station. The model includes three dynamically linked modules to account for all the major components of a typical water budget, including precipitation, canopy interception, overland flow, channel flow, infiltration, evapotranspiration, and saturated groundwater flow. The model is called the Wetlands Dynamic Water Budget Model because it provides magnitudes for the water budget components, as well as water depths, discharges, and flow velocities over different parts of the modeled system. The development of the computer program is based on concepts and approaches of a number of programs in common use. The model was used to simulate various wetland modification scenarios to help build an understanding of how wetlands, like those along the Cache River, function hydrologically. Scenarios included creating various types of constrictions across the wetland, such as might occur with the construction of a highway crossing, channelizing the river by installing levees on the overbanks, and creating wider floodplains by restoring agricultural lands to wetland habitat. NOTE: This file is large. Allow your browser several minutes to download the file.
|Appears in Collections:||Technical Report|