GMSWORKS-3 Peace River Side Channel Restoration - BC Hydro

More documents

Recommendations

Info

identify the opportunities and limitations of each site in terms of the potential to re‐ activate, re‐water or restore habitats; 4. Determine the range of potential engineering works available to provide restoration or re‐watering, including ‘hard’ and ‘soft’ options such as invert excavation, pilot channel excavation, back channel creation or whole channel lowering. 5. Select two or more demonstration sites where various restoration methods, including habitat recreation, construction and bioengineering, can be used in conjunction with re‐ watering options; and 6. Provide a summary of the construction and operational costs for these conceptual options, a decision framework for selection of candidate sites, and rationale for the selection of restoration methodologies. Coordination and synergy with GMSWORKS‐3,‐4,‐5 and ‐6 are further discussed in the summary section of this report. Coordination and data‐sharing between these projects has been enabled by the various contractors, and there are significant opportunities to build on the existing body of knowledge and information collected to date. 2 Data and Methodology Field investigations were undertaken on May 28 and 29, 2009. This involved an initial helicopter survey by the entire study team on May 28. The section of Peace River between Taylor and PCN was flown in both directions. The initially identified sites, along with other potential restoration sites, were inspected from the air and extensively photographed (using both still and high definition video cameras). Selected sites were also investigated on the ground. A second inspection by river boat was undertaken on May 29 by Pattenden and Miles. The 18 km section of river situated downstream of PCN was traversed and potential restoration sites were investigated on the ground. Additional sites were visited by NHC staff during work conducted under GMSWORKS‐5 and ‐6. BC Hydro’s air photo mosaic was unavailable at project initiation and Google Earth imagery was therefore employed. Stream kilometre marks (measured downstream of PCN) and place names were added to assist in site identification. The resulting mosaic, which covers 113 km of river, is of varying quality. High resolution imagery (obtained in 2006) is available in the area between KM 0 to 43 and 49 to 78. Comparatively lower resolution imagery (date unknown) is available between KM 43 to 49 and 79 to 113. Additional analyses and data compilation was undertaken by NHC for side channel configurations and assessment of restoration opportunities along the reach. The mosaics resulting from these additional assessments have been included in the Appendices section of this report. This work has utilized orthophoto mosaics and GIS data provided by BC Hydro and MMA. The basis of the analyses has included an assessment of the physical and biological characteristics of the side channel sites, followed by a technical assessment of the methods and works that could be utilized to restore flow and/or fish access to the sites. This technical information was semi‐qualitative, based on available data, and provided a relative index for Peace River Side Channel Restoration 2
assessment purposes. Data, analyses, results, and summaries have been provided, with relevant information attached. 3 Background Information 3.1 Setting The Peace River is formed by the junction of the Parsnip and Finlay Rivers, and flows eastward through the Rocky Mountains through BC and Alberta to Lake Athabasca. The reach downstream of PCN is underlain mostly by the Fort St. John Shale and Gates Sandstone sedimentary rocks. The most abundant rock formation is Cretaceous Fort St. John Shale of the Shaftsbury formation, which is found frequently exposed along the banks of the Peace River and its tributaries. Near Hudson’s Hope, a sequence of sandstone, shale and silty shale of the Gates Sandstone formation is exposed as islands and banks along the Peace River. These formations are also responsible for the 22 km section of Peace River channel downstream of PCN that is vertically controlled by cross channel exposures of bedrock. Local soils are a product of in situ weathering of the parent rocks that are exposed along the Peace River as well as relic glacial‐derived sediments. The Peace River and tributary valleys have entrenched valley walls composed of fine textured shales and glaciolacustrine sediments. The glaciolacustrine sediments include sand, gravel, and cobbles in a silty sand matrix, weathered fine textured shales and glaciolacustrine slits and clays that were deposited during the recent glaciation by proto‐glacial lakes and ice‐dam floods. Other than localized outcropping of bedrock, the river channel is composed of alluvial deposits of sand, gravel, cobbles and boulders to depths of up to 10 m. More recent alluvial materials within the floodplain area consist of fine textured sands and silts. The Peace River has an entrenched river channel lower than the surrounding plateau by up to 300 m. The Peace River channel is approximately 375 m wide and has a bankfull width of 485 m with a reach slope 0.22 percent 1 . The main river channel is slightly sinuous and often confined by high valley banks. The active channel contains infrequent shoals and bars and relatively regular islands that are partially or fully vegetated and form secondary channels. These secondary or side channels are either free‐flowing, backwatered or non‐functional within the contemporary floodplain. The river morphology and channel processes are further discussed in Section 3.3 3.2 Hydrology and Hydraulics The free‐flowing sections of the Peace River downstream of Hudson’s Hope, BC are regulated by W.A.C. Bennett Dam that has drainage area of which is 68,900 km². The dam has formed Williston Reservoir, which has a live storage capacity of 41,300 Mm³, slightly larger than the average annual inflow volume of developed from a mean annual discharge of 1,100 m³/s. With 1 based on a 2 km cross section spacing from PCN to Fort St. John Peace River Side Channel Restoration 3
Page 1 and 2: Peace River Project Water Use Plan
Page 3 and 4: Executive Summary This study was in
Page 5 and 6: Acknowledgements The authors would
Page 7 and 8: Table of Contents Executive Summary
Page 9: 1 Scope of Work The Peace River’s
Page 13 and 14: Figure 1: Pre‐Regulation Peace Ri
Page 15 and 16: Hydro via telemetry, and will be ut
Page 17 and 18: channel must be sheltered from high
Page 19 and 20: These impacts have been recognized
Page 21 and 22: while the mainstem river area was e
Page 23 and 24: Physical criteria developed in this
Page 25 and 26: a) Inlet improvements for additiona
Page 27 and 28: Studies on the Nechako River indica
Page 29 and 30: Site isolation costs and contingenc
Page 31 and 32: 40.5L 3.0 18.0 Ephemeral Medium 58L
Page 33 and 34: The restoration concept includes: 1
Page 35 and 36: vegetation. The most serious limita
Page 37 and 38: A series of extensively infilled ch
Page 39 and 40: 7.10 River KM 98.2R Site 98.2R cons
Page 41 and 42: compiled at a common scale to docum
Page 43 and 44: Instream Flow Needs Workshop, Walde
Page 45 and 46: Site Summary and Cost Tables Peace

GMSWORKS-3 Peace River Side Channel Restoration - BC Hydro

Create successful ePaper yourself

Delete template?

Save as template?