Citation | Northwest Hydraulic Consultants Ltd. 2010. Cheakamus River Water Use Plan, Monitoring Channel Morphology in Cheakamus River, Implementation Year 2, Study Period: April 2009-April 2010. Prepared for BC Hydro. |
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Organization | BC Hydro |
URL | https://www.bchydro.com/content/dam/hydro/medialib/internet/documents/planning_regulatory/wup/lower_mainland/2010q4/cmsmon-8_yr2_2010-05-14.pdf |
Abstract/Description or Keywords | Hydrometric monitoring has continued at three locations along the Cheakamus River system between Daisy Lake Dam and the Cheekye confluence since February 2008: • Cheakamus River above Chance Creek (Forest Service road bridge below Daisy Lake Dam), hereinafter referred to as ‘Cheakamus FSR’ • Cheakamus River above Culliton Creek (pedestrian suspension bridge over Cheakamus River above Culliton confluence), hereinafter referred to as ‘Cheakamus Pedestrian’ • Culliton Creek above Cheakamus River (Jack Webster bridge over Culliton Creek), hereinafter referred to as ‘Culliton Creek’ Based on discussions with the working group for the Cheakamus Project Water Use Plan Monitoring Program in January 2009 (Monitoring Advisory Committee Meeting), NHC voluntarily undertook additional tributary flow gauging in Year 1 at four additional sites: • Chance Creek above Cheakamus River • Cheakamus River above Cheekye River • Cheekye River above Cheakamus River • Cheakamus River below Cheekye River An additional hydrometric station was also installed in April 2009 on the Cheakamus River below the Cheekye River confluence. This work was carried out to supplement our understanding of tributary flow contributions to the Cheakamus River and to develop rating curves for these sites in anticipation of the need for a greater spatial extent of discharge information on the system by the Monitoring Program working group. Partial rating curves were developed for each of these sites (3‐4 dissimilar discharge measurements at each site) and have been presented in the Year 1 report (NHC, 2009). Rating curve development for the additional sites was discontinued as of June 2009 since there was no apparent interest in expanding the existing Cheakamus River hydrometric network. The Cheakamus River hydrometric station situated below the Cheekye River confluence remains, but has been inaccessible and possibly inoperable since the Cheekeye debris flood in 2009; the station is likely recording data but has been covered by a substantial amount of sediment. Hydrometric stations situated at the above sites continuously log water temperature and water level (stage) data at 15‐minute increments, with barometric pressure and air temperature monitored at the Culliton Creek site. This project requires that flows be estimated at the Cheakamus River sites for a specified range (minimum flow s up to 60 m3 /s), with a full range of flow estimation for the period of record at Culliton Creek, which is the largest single source of inflow between the Daisy Lake Dam and the Cheekye River. Discharge measurements have been used to further refine the rating curves submitted in the Year 1 report (NHC, 2009). Changes in channel geometry can cause the relation between stage and discharge to change over time. For example, channel erosion or deposition during storms events, or the placement of bank protection works, can affect the stage‐discharge relation. For this reason, water levels are physically measured during each site visit and compared to transducer stage data to ensure the accuracy of the instrumentation over time. Each new discharge measurement is also compared against the existing rating curve and the yearly stage record to determine if a new rating curve must be developed following a high flow event or a shift in the stage data. Instantaneous measurements of flow for the development of site‐specific stage‐discharge rating curves have been conducted using a variety of methods. When possible, we have employed a velocity‐area approach to estimate instantaneous discharge on the Cheakamus mainstem with an Acoustic Doppler Current Profiler (ADCP) 1 . If stream flow conditions are not suitable for this method, our second choice is to utilize either mechanical or acoustic velocity meters to provide mean velocities at a minimum of 20 or more intervals across a stream cross‐section (RISC, 2009). A Price® velocity meter was utilized for this method on only one instance at the Cheakamus Pedestrian site (Table 2). Excessively turbulent stream conditions, such as at Culliton Creek, preclude the use of acoustic or mechanical velocity meters, but instantaneous flows have been successfully measured with salt dilution and Rhodamine WT dilution gauging methods. Details on flow gauging and monitoring methodologies are briefly described in subsequent sections, and for more detail the reader is referred to the following publications (attached): 1) Moore (2004a, 2004b, & 2005) and Hudson and Fraser (2005) for salt dilution methods, and 2) Teledyne RD Instruments (2009a & 2009b) for acoustic profiling methods. Rhodamine WT dilution is analogous to the salt dilution method. Rating curves are provided in Figure 1 ‐ Figure 3 along with extrapolation lines indicating the limit above which flow hydrograph estimates for each site are beyond the range of measured flows. Instantaneous discharge measurement errors are provided in Table 2, where error bounds are one standard deviation for ADCP measurements, and 10% for dilution and velocity‐area methods. Mean daily streamflow hydrographs are provided in Figure 4 ‐ Figure 6 for each site, with water and air temperate from the Culliton Creek site. |
Information Type | report |
Regional Watershed | Howe Sound & Sunshine Coast |
Sub-watershed if known | Cheakamus River |
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Project status | complete |
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