brownsville dam removal - effectiveness monitoring
the tullos lab at Oregon State University is investigating physical and biological responses of the removal of Brownsville Dam on the Calapooia River. Changes in sediment dynamics, channel morphology, invertebrate communities, and riparian habitat are being investigated.
The Brownsville Dam was located at river km 62, about 4 km southeast of the city of Brownsville. It was originally built as a log crib dam in the late 1800's, to divert water into the Brownsville Canal providing water for a variety of mills. The dam failed in the 1940's and was rebuilt in the late 1960's as concrete shell filled with sand and gravel to divert flow into the canal for aesthetic purposes. Removal of the dam was completed in the summer of 2007. The dam was 33.5 m wide with a 4.3 m apron. Historically, the upstream height of the dam was increased from 2.4 meters to 4 meters using flashboards to enable diversion of water into the canal during the low flow period from the end of May to the beginning of October. During this summer season, the ratio of reservoir width to channel width was 2.2, reflecting the doubling of channel width along the reservoir section. This run-of-river reservoir was filled with sediment, storing approximately 14,000 m3 of gravel (D50 = 59 mm).
