| Abstract/Description or Keywords |
A group of Elk Valley local government officials and staff, industry representatives, and community members met at a critical meeting hosted at the City of Fernie chamber in July following the June 2013 flood. Participants agreed that the following were needed: 1) a better understanding of the current and future condition of the Elk River and its flooding behaviour; and, 2) a holistic flood strategy protecting residents, community infrastructure, as well as watershed function and wildlife. The Elk River Watershed Alliance (ERA) is an independent, non-profit community-based water group formed in 2010 that promotes a holistic approach to management of human actions in the Elk River watershed. ERA took on the challenge to coordinate the collection of the above requested information, and community input for proactive flood management. The Elk River Flood Strategy report (Flood Strategy) provides a review of how the local watershed functions within the larger environment, current and forecasted streamflow and flooding in the Elk Valley, effects of flooding on community, fish and wildlife, and effective measures available to help mitigate against future flood risk. The Flood Strategy team had substantive professional and local Elk River watershed experience, and included: the ERA, contractors, academics, local government staff, and dedicated ERA board members as a review team. Team backgrounds were diverse, including: environmental management, aquatic biology, municipal and water engineering, hydrology, hydraulics, and computer modelling. Elk Valley residents who experienced past flooding, provided critical observations and analysis of our local response, as well as suggestions for moving forward as a resilient, prepared citizenry and community. Analysis of flooding in the Elk River (Section 3) Flooding on the Elk River was analyzed first by discussing the conceptual framework of a watershed. A quantitative analysis was then completed of the hydrology of the Elk River and tributaries, with particular emphasis on the conditions that result in flooding and how these are affected by land use and climate change. Watershed function and the interconnectedness between hydrology, ecology, and water quality were investigated. This addressed how changes to one element invariably affects the others, and that while a watershed can withstand a certain degree of change, dramatic or cumulative disturbance can eventually lead to a shift in watershed response. Effective watershed management going forward must recognize that natural and human activity within the Elk Valley invariably affects watershed function and can cause fragmentation and a loss of diversity, both of which can further reduce the watershed’s resiliency to future disturbances. The hydrologic regime of the Elk River at Fernie was examined. A review of the three largest floods on record in the Elk Valley (2013, 1995 and 1974), showed that flooding occurs almost exclusively during this peak flow period, and that extreme floods are typically preceded by extreme rainfall events coinciding with near-peak snowmelt. A statistical evaluation of the observed changes to the hydro-meteorological drivers of flooding in the Elk Valley suggests that there has been an increase in spring rainfall and winter snowpack since 1970, although this does not appear to have manifested itself as an increase in average streamflow in the valley. Effects of flooding on community (Section 4) To provide a comprehensive picture of the history of flooding in the Elk Valley, archived photos and documents were reviewed from the Fernie Free Press (1902-present), the Fernie and District Historical Society, and the Sparwood Public Library archives. Flood history was obtained from various local and regional media, local government notices, and flood hazard assessment reports from mid 1990s to June 2016 present. Using this information, the chronology of floods in the watershed, resulting damage, emergency actions deployed, and responses of the communities were summarized. From May to September 2015, two community outreach flood educators attended 23 events, where they reached over 1,400 residents about flooding in the Elk Valley. Surveys were solicited at these events and on-line through the ERA website, which 200 people completed. Survey respondents were spread approximately in proportion to populations of Elk Valley communities. Additionally, eighteen oral history interviews were conducted with residents of the Elk Valley. These anecdotal impressions of past flooding events were valuable in framing the picture of community experience and attitude to flooding, and in compiling past experiences of flood mitigation and community response. During January and February 2015, Lee-Anne Walker, ERA Executive Director delivered an Elk River Flood Strategy overview presentation to the Districts of Elkford and Sparwood, City of Fernie, Elk Valley Cumulative Effects Management Framework (CEMF) working group and Elk Valley Integrated Resource Task Force. The main goal of these presentations was to gather input from municipal leaders about their key questions with regards to flooding in the Elk Valley, and how ERA’s Flood Strategy could best support their decision making. ERA hosted 40 participants at the Elk River Flood Strategy Technical Review Workshop on October 14, 2015 and the same number at the Solutions Symposium for Flooding in the Elk River Watershed April 12, 2016. The objectives of these two workshops were to check back with the community on key findings and outcomes throughout the process and obtain critical feedback and advice on how to implement the Flood Strategy recommendations. Effects of flooding on fish and wildlife, and mitigation options that improve habitat (Section 5) A literature review was completed on the effects of flooding and flood mitigation works on fish and wildlife. The floodplain of the Elk River Valley provides important habitat for many fish and wildlife species, including many sensitive species. Riparian areas are the transition area between aquatic and upland habitats; these areas support distinct plant species, and provide many essential watershed, aquatic life, and wildlife functions. Black cottonwood riparian stands and wetlands are specific habitats of importance in the Elk River floodplain. These areas all have the greatest potential to be influenced by flood and flood mitigation practices. Floods often have positive effects on fish populations (e.g., by stimulating invertebrate production, and triggering spawning for certain species), but can also potentially have negative impacts on fish populations, particularly recently hatched and juvenile life-stages, which can be overtaken by high flows. Maintaining hydraulically complex streams through responsible land management practices, is important to increase the ability of fish and habitats to positively respond to flood events. The morphology of the Elk River in the study area is riffle-pool channel type. The value of fish habitat in this channel type is determined largely by channel pattern, bar type, large woody debris, and stability. These habitats can become negatively impacted under aggrading or degrading sediment supply conditions, as a more uniform channel is created. In addition to immediate direct riparian habitat losses, traditional flood mitigation such as dike and rip rap installations, can result in channel degradation (sediment supply being limited). Examples of channel degradation impacts include: extensive riffles and runs; decreased pool frequency, size and depth; cut off side channel and off-channel habitats; cobble and courser texture sediment size; and limited large woody debris, with those present oriented parallel to the banks. These changes can impact fish diversity and abundance. Smart land use planning, which considers preserving the natural floodplain as a priority, should be a precursor to installation of traditional flood mitigation measures for the protection of fish and wildlife habitats. When planning for flood mitigation, the following over-riding principles were suggested: 1) use traditional hard approaches only when necessary, 2) limit footprint size, 3) limit narrowing, straightening and cutting off the floodplain, 4) set-back installations, and 5) incorporate natural habitat elements. Visual examples of habitat features incorporated into traditional flood mitigation works were provided (e.g., setback dike, vegetated dike and rip rap, rock groins, and bioengineering). Simulating floods in the Elk Valley (Section 6) Historical streamflow for the Elk River at Fernie was simulated using process-based hydrological modelling. The model represented daily average streamflow conditions for the Elk River reasonably well, and was subsequently used to evaluate streamflow response to land use and climate change. The Climate BC version 5.21 tool (Wang et al. 2012) was used to obtain two future climate change scenarios (RCP 4.5 and RCP 8.5) for one general circulation model (Can ESM2) for the period from 2011 to 2041. These future climate change scenarios represent greenhouse gas concentration pathways (RCP) that are focused on when greenhouse gas concentrations will stabilize. The RCP 4.5 assumes radiative forcings will stabilize at 4.5 Watts per meter squared (W m2) by the year 2100, while RCP 8.5 is comparatively higher at 8.5 W m2 by 2100. In general air temperatures are projected to increase under these scenarios, and so is winter precipitation. Summer precipitation is projected to decrease. Land use change was simulated as a 3,100 hectare (ha) forest harvest scenario, representing approximately 5 years of timber harvest at the current annual allowable cut in the Elk Valley. It was also assumed that harvest area would not exceed 10 ha and would be distributed randomly below an elevation of 2000 m above sea level. Future streamflow simulations suggest that climate change has an over-arching effect relative to land use change, and that runoff is expected to be earlier in the spring period. Simulations also suggest that higher snowpack in the winter could result in higher spring streamflow on average. Land use change scenarios resulted in slight streamflow increases early in the spring and slight decreases during June. The effect of land use change is largely due to desynchronization of snowmelt runoff from lower elevations where forest cover was removed. In addition to hydrologic modelling, a hydraulic model was developed for the Elk River between the townsite of Hosmer and Coal Creek. This model was based on high resolution digital elevation data and field surveys and provides a means of evaluating the relative differences in inundation between different flood events. It is important to recognize that this model is not intended to be an exact replication of particular events, nor is it meant to provide exact information on inundation. This is a screening-level tool that provides value in assessing relative effects of events. A web-based visualization tool was developed (elkriveralliance.watersimulation.ca) to help facilitate the delivery of this information to a broad audience. Recommended non-structural and structural flood management strategies (Section 7) Flooding is only a problem when it affects people and properties. A qualitative overview was undertaken of the major non-structural and structural flood management strategies that have been employed in Western Canada and internationally, with a particular emphasis on methods with demonstrated effectiveness that also preserve watershed function and diversity. Widely-used non-structural flood management measures including emergency planning and response, homeowner preparedness such as flood-proofing, and municipal planning were reviewed. Structural mitigation options, including storage infrastructure (dry-dams and reservoirs), floodwalls, diversions, and channelization projects, can span a wide range of costs and environmental impacts. Given the current scientific understanding of the interconnectedness between watershed hydrology, ecology and water quality, it is important that flood mitigation measures aim to maintain the natural integrity of the watershed. It was recommended that planning occur with the erodible corridor concept in mind to leave a wide belt which within the river channel can freely move and flood, for ecological conservation and to minimize future conflicts between human settlement and bank erosion processes. Non-structural measures, such as renaturation of the floodplains, restoration of riparian areas and wetlands, and land use best management practices, provide flood mitigation options that are both effective at reducing flood damage and promoting natural hydrological processes. There are several properties in the RDEK, situated in the Elk River floodplain with potential flood and/or erosion issues. Sites were identified by the consulting team and RDEK staff as key areas to investigate. Concept designs and associated cost-estimates were developed to further prioritize the sites, identify additional study requirements, and seek infrastructure funding. These concept designs are in a separate report. Informing local decision makers and community with flood strategy tools (Section 8) An analysis of flood planning and management from the 1990s throughout the Elk River watershed revealed that communities have actively studied the issue of flood hazard and mitigation, raised money for flood protection, and modified planning to keep in step with changing land use and climatic conditions. This Elk River Flood Strategy recognizes the value of this past work and wishes to integrate and build on these previous efforts. The Solutions Symposium on Flooding in the Elk Watershed was held on April 12, 2016 at the Fernie Arts Station. The symposium was attended by 40 key decision makers and residents. Key findings from the Flood Strategy were presented. Participants provided direct input on specific actions or recommendations toward proactive, holistic watershed scale flood management and protection in the Elk River Watershed. Specific recommendations stemming from this report and associated community input are: 1. Continue to build on this flood strategy, using an integrated, collaborative and coordinated approach to flood management and mitigation. _ Encourage all levels of government, industry and community to continue to collaborate on holistic, watershed wide flood strategies. _ Adopt the Elk River Flood Strategy as a first step toward an integrated Elk River Watershed Flood Management Plan. _ Form an Elk River Flood Management Committee, empowering local watershed governance as stated in the new BC Water Sustainability Act. This Committee could be initially facilitated by the Elk River Alliance. _ Exercise existing regulations, policy and political will to limit, where possible, development in the floodplain. _ Work with private land owners in the Elk Valley to address community concerns about flood impacts from private land. _ Continue with hydraulic modeling in high priority areas in the Elk River Watershed, similar to that which the Flood Strategy produced between the townsite of Hosmer and Coal Creek mouth. This product provides a tool to aid decision makers and residents in visualizing various flood inundation scenarios. 2. Keep people safe from flood risks. _ Recognize the impacts of flooding on individual homeowners and educate watershed residents with practical solutions that they can take to be prepared for future flood impacts. _ Talk with residents about their local knowledge and experience with flooding and consider this input throughout the decision-making process. _ Continue to increase our collective watershed literacy about flooding. 3. Protect key infrastructure. _ Employ proactive flood management and mitigation approaches that are effective, use tax resources wisely, increase watershed resilience, and protect habitat. Avoid reactive ‘quick fix/nonstrategic’ actions. _ Monitor and maintain existing flood infrastructure (e.g., dikes, and streambank erosion protection) in good working condition to protect citizens. _ Restrict dredging, as the cost to the river ecology outweighs the perceived short-term benefits. _ Where diking and riprap are required to protect key infrastructure, incorporate natural habitat elements to offset impacts to fish and wildlife habitat. June 2016 xi _ Where possible, protect and re-establish riparian areas, wetlands and off-channel habitats. 4. Respect the natural function of the watershed to provide a buffer of resilience to climate change. _ Use the understanding of Elk River hydrology, geomorphology, and effects of flooding on fish and wildlife to guide flood management and mitigation decisions. _ Recognize that natural and human activity in the Elk Valley affects watershed function, and can cause fragmentation and a loss of diversity. Therefore, limit development in the erodible corridor (valley bottom) to the furthest extent possible, to maintain ecological function. _ When implementing structural flood mitigation, limit narrowing, straightening and cutting off the floodplain from the Elk River and tributaries. _ Promote best flood management practices for developers and private landowners in flood prone areas. _ Promote best management practices with municipalities regarding stormwater management, riparian protection, and erosion protection to reduce sediment in the Elk River and its tributaries, in order to protect aquatic habitat. _ Acknowledge that crisis in the watershed can oscillate between floods and droughts; therefore, plan for mitigation measures to address both extremes. |
