Hydrologic Analysis for a Floodplain Forest Wetland Mitigation Site
Publication: World Environmental and Water Resource Congress 2006: Examining the Confluence of Environmental and Water Concerns
Abstract
The Fournier floodplain forest mitigation site is a 5-acre wetland design north of Stevens Point, Wisconsin, located within the 100-year floodplain of the Wisconsin River. The surface water level on the site is regulated by a dam downstream. The floodplain forest mitigation site was created by grading the ground surface down to a more frequent flood elevation and then planting the site with the appropriate floodplain forest trees and shrubs. Critical to the success of the mitigation is grading the appropriate ground elevation. While some surface flooding is necessary, research indicates it is not desirable to have prolonged flooding over restored floodplain forests because of reduced tree seedling and sapling survival rates. Surveyed land surface and water elevations, groundwater elevations, river flow data and hydraulic modeling analysis were used to analyze the wetland hydroperiod for the site. A hydraulic computer model, HEC-RAS, was used to calculate water surface elevations for a range of flow rates. HEC-RAS was used to model both steady state (constant flow rate) and unsteady state (varying flow rate over time) conditions. The calculated water surface elevations from the steady state and unsteady state models have over a foot of difference at flood flow rates. Initially it was thought that the unsteady state model would more accurately depict actual stage conditions because flow in actual conditions does vary over time. However, the steady state model results are more consistent with the available measured data. The hydroperiods developed from both the steady state and unsteady state model results were used to determine a grading elevation that floods annually but not flooded for such long periods of time as to inhibit tree sapling survivability. The selected grading elevation met this criteria according to the hydroperiods developed from both models. Measured water surface levels from the spring flood of 2006 will be compared to the model data to further verify the modeling results.
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Copyright
© 2006 American Society of Civil Engineers.
History
Published online: Apr 26, 2012
ASCE Technical Topics:
- Business management
- Ecosystems
- Engineering fundamentals
- Environmental engineering
- Floods
- Forests
- Geotechnical engineering
- Geotechnical investigation
- Hydraulic models
- Hydrologic engineering
- Hydrologic models
- Hydrology
- Mitigation and remediation
- Models (by type)
- Practice and Profession
- River engineering
- River systems
- Site investigation
- Water and water resources
- Wetlands (fresh water)
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