Stormwater Infrastructure Climate Change Vulnerability Assessment

In 2009, the Columbia Basin Trust provided the City of Castlegar with funding to apply Engineers Canada’s Public Infrastructure Engineering Vulnerability Committee (PIEVC) Engineering Protocol for Climate Change Infrastructure Vulnerability Assessment. The study focused on the impact of climate change on the city’s stormwater infrastructure, as local officials and other stakeholders were concerned that changes to watersheds surrounding Castlegar threatened the reliability of local stormwater infrastructure. Castlegar conducted a vulnerability risk assessment of stormwater infrastructure under PIEVC protocol to identify the components most vulnerable to climate change impacts. The protocol followed five distinct steps: project definition, data gathering and sufficiency, risk assessment, engineering analysis, and recommendations. A team from the Pacific Climate Impact Consortium helped develop climate models for the City of Castlegar that projected more rain and less snow, with an increased risk of extreme rainfall events that could lead to more frequent and larger flow events in streams and stormwater management systems. The climate projections and vulnerability assessments revealed that Castlegar was indeed vulnerable to climate change. Specifically, after applying 11 climate change events to 35 infrastructure elements, it was determined that 34 of the 35 stormwater infrastructure elements studied in Castlegar were at medium or high risk, including 10 at high risk. The study informed recommendations which included reviewing the 10 high risk infrastructure elements to develop an action plan with timelines and budgets. Actions such as the development of a mitigation strategy to prevent erosion for a creek, resizing certain culverts and storm sewer trunks, and improving sections of a stream channel to carry expected peak flow were amongst the specific recommendations of the study. The Stormwater Infrastructure Climate Change Vulnerability Assessment contributed to several infrastructure rehabilitation efforts since 2012 and helped develop a comprehensive climate change adaptation strategy for the City of Castlegar.

Understanding and Assessing Impacts

The expectation that waste and stormwater infrastructure may be in place for 50 to 100 years makes it paramount to address both historic and future climate considerations. Climate models have emerged in recent years as a new tool available to local governments, such as the City of Castlegar’s, to manage the impact of extreme rainfall due to climate change on waste and stormwater infrastructure. Tools such as Engineers Canada’s PIEVC protocol were developed for municipalities like Castlegar to assess exactly what risks are posed by extreme rainfall and how they can be accommodated in stormwater infrastructure design, maintenance, and operations. Cost and benefit analyses were an extremely useful tool, as they revealed that in several instances a 15 to 20 percent increase in the volume of waste and stormwater flows may add one percent to the initial cost of construction, but it would help avoid the risk that the infrastructure becomes prematurely obsolete and needs to be replaced in 20 or 30 years because it is unable to cope with predictable increases in flows. Knowing that in several instances, a small additional investment in waste and stormwater infrastructure would have an excellent payoff in the long-run prompted the City of Castlegar to apply for funding to assess the impact of climate change on the city’s infrastructure. Thus, with the funding of the Columbia Basin Trust, Castlegar was able to apply Engineers Canada’s PIEVC Engineering Protocol for a Climate Change Infrastructure Vulnerability Assessment. After identifying the significant threats climate change posed to local infrastructure, the City of Castlegar was able to begin developing a plan for how to work with stakeholders to analyze historical climate data, develop future climate models, analyze specific climate scenarios, and ultimately build a catalogue of vulnerable infrastructure based on PIEVC protocol that would inform proactive climate change adaptation plans in the future.

Identifying Actions

The Columbia Basin Trust gave Castlegar funding to launch the study that would lead to recommendations based on the PIEVC infrastructure assessment. The protocol used for the study consisted of the following five specific steps: project definition, data gathering and sufficiency, risk assessment, engineering analysis, and recommendations. The first step involved developing system boundaries for an adequate assessment of infrastructure vulnerabilities. To achieve this, the City first considered stormwater infrastructure in a broader context. They looked at catchment and various drainage areas, physical infrastructure and operations, maintenance and resource requirements for stormwater management. It was decided that the approach to the study would be to focus on the infrastructure draining five upland catchments since they were the most likely to be impacted by climate change. A team from the Pacific Climate Impact Consortium was involved in the project to help assess the local probabilities of climate change, including shifts in the intensity, duration, and frequency of extreme rainfall events. These forecasts would allow Castlegar to assess the vulnerability of their infrastructure to future climate change impacts. Involving various organizations such as the Pacific Climate Impact Consortium in both the planning and implementation of the project was fundamental to its success. The Public Works Department in Castlegar also contributed when selecting infrastructure to test. Chris Barlow, Director of Transportation and Civic Works for the City of Castlegar, mentioned, “When we first looked at vulnerabilities, we brought in our Public Works Department. They are the front line guys and the ones that are the most aware of what is really happening in the field. Bringing these people into this training helped a lot.”

Implementation

After outlining an approach and objectives for the Stormwater Infrastructure Climate Change Vulnerability Assessment, the City of Castlegar worked with various shareholders to develop climate models and assess waste and stormwater infrastructure vulnerabilities. The Pacific Climate Impact Consortium developed models that projected more rain and less snow in Castlegar. A concerning trend was the expected increased risk of extreme rainfall events that could result in more frequent and larger flow events in the streams and stormwater management systems, putting increased stress on the community’s infrastructure. The City of Castlegar proceeded by applying 11 climate change events to the 35 identified infrastructure elements which produced very telling results (see outcomes section). The final step in the implementation phase of the study was to draw implications from the scenario testing and vulnerability assessments to inform and prioritize adaptation actions. When Castlegar faced heavy rain events in the spring of 2012, the City conducted infrastructure workshops with the Public Works Department to explain which infrastructure elements were identified as the most vulnerable in the study which commenced in 2009. Involving multiple stakeholders to obtain several perspectives on the issue was an important part of the implementation process. Castlegar’s Director of Transportation and Civic Works emphasized the benefits of involving front-line workers in the Public Works Department: “Some of the projects we decided to work on were related to the study and some others were things we noticed by looking closer in the field by looking at specific elements and wondering how much of a risk they were. This process brought up things we never questioned before and encouraged us to do more preventative work.” Hosting informative workshops and stimulating discussion with people on the front lines gave the City of Castlegar another avenue of information to supplement the findings of the study when deciding which recommendations to pursue further and how to prioritize future adaptation initiatives.

Outcomes and Monitoring Progress

The study conducted under PIEVC protocol indicated that the City of Castlegar was vulnerable to climate change. The 11 climate change events applied to 35 infrastructure elements revealed 313 interactions that were considered to have a cause-and-effect relationship necessitating further assessment. This assessment revealed that 34 of the 35 stormwater infrastructure elements studied were at medium or high risk, with 10 at high risk. The most significant outcomes of the study were the recommendations that were made based on the comprehensive risk assessments. The study recommended a review of the 10 high-risk infrastructure elements. It was important for the City to develop an action plan to address these issues and explore funding opportunities at the provincial level to rehabilitate these infrastructure elements. More recommendations to address the 10 high-risk elements included the development of a mitigation strategy to prevent erosion for a creek, resizing certain culverts and storm sewer trunks, and improving sections of a stream channel to carry expected peak flow. These suggestions are indicative of the success of the overall project; Castlegar succeeded in achieving their goal of assessing vulnerabilities to develop key insights on necessary adaptation actions. Another outcome of the study was that it brought a change in the way the City was monitoring extreme rainfall events. The PIEVC report identified that inlets and outlets were a major issue for Castlegar. Consequently, the City started to monitor weather forecasts more closely and sent a crew to check inlets and outlets every time a heavy rain event occurred. Since 2012, many large stormwater infrastructure projects were completed based on the recommendations of the study. These projects included the installation of storm sewers in areas that were washed out during previous storm events and the addition of curb gutters. Finally, the Stormwater Infrastructure Climate Change Vulnerability Assessment also contributed to the development of a comprehensive climate change adaptation strategy for the City of Castlegar.

Next Steps

With a strong understanding of the vulnerabilities to climate change in the municipal infrastructure, the City of Castlegar’s next steps include following the recommendations of the study by introducing further adaptation measures. The City is involving the Public Works Department in analyzing vulnerable infrastructure by hosting workshops to facilitate discussions about which other elements might have been identified as vulnerable by the workers. Moving forward, this type of engagement offers Castlegar another perspective when it comes to identifying vulnerabilities and risks of specific elements that may not have been included in the Stormwater Infrastructure Climate Change Vulnerability Assessment project. Despite completing an immersive study, continued monitoring of vulnerable waste and stormwater infrastructure throughout the community remains a priority for the City of Castlegar. Mr. Barlow indicated that the City is encouraged to “do more preventative work” moving forward. Another outcome of the study that will certainly involve further action is the development of a learning network. The City of Castlegar became part of a learning network established by the Columbia Basin Trust to support other Basin communities with climate change adaptation. Castlegar has a lot to offer in terms of sharing lessons learned with communities in the learning network aspiring to conduct similar vulnerability assessments. Castlegar can also take lessons in other areas of climate change adaptation from members of the learning network that will continue to grow with time. However, the major focus of the next steps for Castlegar will be the continued implementation of a number of actions to rehabilitate vulnerable stormwater infrastructure based on the timely recommendations made through the PIEVC assessment.

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Additional Resources