Water Stewardship Information Sources
| ID | 1712 |
|---|---|
| Citation | Summit Environmental Consultants Ltd. 2012. Shuswap Project Water Use Plan: Flooding Risks in the Middle Shuswap River, Implementation Year 1, Final Report, Study Period: May 2008 - June 2011. Prepared for BC Hydro. |
| Organization | BC Hydro |
| URL | http://www.bchydro.com/content/dam/hydro/medialib/internet/documents/planning_regulatory/wup/southern_interior/2012q2/shumon-3_yr1_2012-05-18.pdf |
| Abstract/Description or Keywords | In 2006, BC Hydro developed a terms of reference (TOR) for effectiveness monitoring programs, which were aimed at providing BC Hydro with information upon which to base future operating decisions. The TOR outlined a monitoring program ﾓSHUMON-3 Flooding Risks in Middle Shuswap Riverﾔ for the completion of a one-year study to determine if a flood performance measure of 232 m3 /s at Wilsey Dam was appropriate for identifying flooding risks in the Middle Shuswap River. A field monitoring program was implemented in 2008 to provide an assessment of flood conditions within the Middle Shuswap River at three (3) sites to test the hypothesis that overbank flooding occurred when discharge at Wilsey Dam reached 232 m3 /s. The three sites were identified as Site 1 - Huwer Property, Site 2 - Huwer Bridge, and Site 3 - Procter Property. At each site, staff plates, benchmarks, and photopoints were installed and topographic surveys were completed in 2008. However, the required flow (232 m3 /s) did not occur until June 2011. The flood monitoring sites were visited six (6) times from 2008 to 2011, which included field examination of flood extents in May 2008 and June 2011, in addition to a helicopter survey of the entire Middle Shuswap River completed by BC Hydro in 2006. During the helicopter survey and field reviews, overbank flooding was observed at all three flood monitoring sites. The extent of flooding at Site 2 - Huwer Bridge had been reduced after 2006, due to bank stabilization work and the installation of a rock dyke by Fisheries and Oceans Canada. Overbank flooding at Site 1 - Huwer Property and Site 3 - Procter Property was observed to occur along the channel at numerous locations, which resulted in the ponding of water in the fields adjacent to the channel and the reactivation of an abandoned channel at Site 3 - Procter Property. Pothole flooding was also present at the monitoring sites, a result of an increase in the water table elevation. The extent of overbank flooding was similar during the 2006 helicopter survey and the 2011 field review due to the similar discharges measured at Wilsey Dam (approximately 237 to 240 m3 /s). Flooding was just beginning during the 2008 field review, when the discharge at Wilsey Dam was approximately 200 m3 /s, which suggested that the hypothesis that overbank flooding occurs at a discharge of 232 m3 /s at Wilsey Dam (identified in the TOR) was incorrect. Unregulated streamflows entering the Middle Shuswap River downstream of Wilsey Dam and above the three sites are also relevant for flood management within the Middle Shuswap River. The largest contribution of streamflow to the Middle Shuswap River below Wilsey Dam is from Bessette Creek. In 2008, the estimated discharge in the Middle Shuswap River the point that overbank flooding began was 234 - 239 m3 /s, comprised of 200 m3 /s at Wilsey Dam, 29 m3 /s at Bessette Creek, and an estimated 5 - 11 m3 /s from other non-monitored tributaries. Based on the results of this investigation, it is recommended that in order to limit flooding adjacent to the Middle Shuswap River, the outflows from Sugar Lake should be managed to meet a target of 229 m3 /s within the Middle Shuswap River based on the combination of discharge at Wilsey Dam and on Bessette Creek. It is also recommended to upgrade the Bessette Creek station to provide real-time flow and water level data; and to confirm the assumption of a one-day lag time between Sugar Lake and Wilsey Dam. The benefit of following the recommendations contained herein may be greater than using the 232 m3 /s target originally suggested by BC Hydro (2002), as the target of 229 m3 /s (from the combination of discharge at Wilsey Dam and Bessette Creek) indicated an additional 35 days (i.e. approximately 1.3 days per year on average) when flooding likely occurred adjacent to the Middle Shuswap River as compared to that originally estimated over 1974-2000. flood, streamflow, low flow, peak flow, fisheries, erosion |
| Information Type | report |
| Regional Watershed | Shuswap |
| Sub-watershed if known | Shuswap River |
| Aquifer # | |
| Comments | |
| Project status | complete |
| Contact Name | |
| Contact Email |