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Ground Water Pore-Pressure Influences on Stream Restoration
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.orgCitation: Paper number 701P0904, . (doi: 10.13031/2013.17375)
Authors: J.A. Magner, O. Baird. K.J. Kuehner
Keywords: River Restoration, Ground water, Fish Habitat
Ground water exchange with stream channel beds can produce unique restoration challenges. Ground water flow into alluvial substrate stream channels can weaken boundary shear strength of the channel bed. Bed instability limits the quality of aquatic habitat. Channel stability was evaluated on the lower reach of Seven Mile Creek, an 86-km2 trout stream in south-central Minnesota. Based on assessment a 330-m was restored in a county park using natural channel design techniques. Detailed geomorphic data was collected from the incised stream to flatten channel grade, create pools, and establish a meander bend point bar. A track-hoe was used to excavate bed and bank materials, and place large natural rock and root wades for channel and habitat restoration. For less than $50 per linear meter the restoration activities were generally successful for infrastructure protection based on post storm channel inspection. A before-and-after trout survey indicates that trout populations may have improved with increased percent of pools and enhanced riffle quality. Designed pool depths were not achievable because ground water pore-pressures collapsed pool side-walls when the depth exceeded more than 1.06-m or a side-wall angle greater than 11.4 degrees. Placement of footer rock below cross-vanes and J-hook rock vanes was limited to one boulder because sub-bed material collapsed into the excavation within seconds of track-hoe bucket removal. The consideration of ground water pore-pressure should be included in stream restoration designs that interact with ground water discharge zones.(Download PDF) (Export to EndNotes)