Whychus Creek Irrigation Dam Removal & Channel Restoration

Whychus Creek Irrigation Dam Removal and Channel RestorationWhychus Creek’s drainage covers a total of 230 square miles beginning in the Three Sisters Wilderness, and extending north-eastward through the Deschutes National Forest, the City of Sisters, private agricultural land, and sagebrush steppe upland before discharging to the Deschutes River.  Historically, Whychus Creek has occupied many different locations across its deposited alluvial fan.  As the City has grown and expanded along and around Whychus Creek through the years, the creek’s dynamic responses to changes in land use, flooding, channel instability, and bank erosion threatens property, public safety and the health of the creek.

Whychus Creek is located in a relatively-fixed position as it flows through the City.  Left to natural processes, Whychus Creek would continue to migrate laterally across its outwash plain.  In addition, the creek being mainly snow melt driven displays great variations in flows both on a daily and seasonal basis.  Flooding events are not uncommon, especially in the fall and early winter when rain-on-snow events occur.  In many instances homes have been constructed within the Federal Emergency Management Agency (FEMA) 100 year floodplain or within the channel migration zone (CMZ).

AfterUnder a design-build contract with the Upper Deschutes Watershed Council, HENDERSON is evaluating dam removal and stream channel restoration alternatives.  Our team’s technical analysis and design development of the Whychus Creek Irrigation diversion dam Removal effort will build upon the community consensus that UDWC has generated with the City and project shareholders.  HENDERSON professionals are developing designs to deter embankment erosion within the existing channel constrained by the irrigation diversion dam, and to restore potential floodplain capacity, embankment stability, sediment transport, and fishery habitat within this reach of Whychus Creek after dam removal.  Final restoration design will address the issues still facing the community, focusing strongly on protection of property and the bioengineered stabilization of adjacent floodplain and channel embankments, while balancing resource objectives for in-water fisheries habitat and native riparian plant communities.  Our final design will integrate the habitat needs of all life stages for summer steelhead, redband trout, and spring Chinook salmon as well as primary fishery limiting factors including; limited structural diversity, lack of large woody material, pools, undercut banks, and gravel streambed features.

Website Design by BOING