American Society of Civil Engineers


Forensic Hydrodynamic Evaluation Following the Restoration of a Tidal Freshwater Wetlands


by Stephen Breithaupt, (Scientist, - Pacific Northwest National Laboratory, Battelle Seattle Research Center. 1100 Dexter Avenue North, Suite 400, Seattle, WA 98109) and Tarang Khangaonkar, (Research Leader, - Water Resources Modeling. Pacific Northwest National Laboratory, Battelle Seattle Research Center. 1100 Dexter Avenue North, Suite 400, Seattle, WA 98109)
Section: Water Quality Modeling II, pp. 618-632, (doi:  http://dx.doi.org/10.1061/40990(324)34)

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Document type: Conference Proceeding Paper
Part of: Estuarine and Coastal Modeling (2007)
Abstract: The Kandoll Road Restoration Project modified the existing structures on Kandoll Farm to return the farm to a freshwater tidal wetland. The farm is located on the Grays River, Washington that flows into the Columbia River at approximately river mile 24. Grays River is subject to the tidal and upstream flow conditions of the Columbia River. The restoration involved breaching the Grays River dike in three locations, installing two 13-ft culverts, and changing the elevation of Kandoll Road. These restoration actions were completed in August 2005. In late December 2005 and mid-January 2006, flooding occurred in the Grays River floodplain including the restoration area and adjacent areas offsite. A hydrodynamic modeling evaluation was done using the model RMA2 to determine the cause of the off-site flooding. The model was calibrated using available hydraulic data collected during the restoration evaluation which included the period of flooding. From the hydrodynamic modeling analyses, two types of flooding events were found to have occurred in December 2005 and January 2006. The first type was a tidally-induced flood event originating with higher-than-normal water levels in the Columbia River. This resulted in the overtopping of Kandoll Road from the restoration side and flooding of the offsite area adjacent to the restoration site. The second type was a river flooding event originating from high runoff upstream. This caused overtopping of dikes upstream of the offsite area, and overtopping Kandoll Road from the north.


ASCE Subject Headings:
Forensic engineering
Hydrodynamics
Restoration
Tidal currents
Wetlands
Fresh water