Vulnerability and Risk Assessment
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Vulnerability and Risk Assessment March 2018 Summary of Findings The City of Olympia (City), Port of Olympia (Port), and LOTT Clean Water Alliance (LOTT), collectively referred to as the Project Team, conducted a sea level rise (SLR) vulnerability and risk assessment to evaluate flooding and SLR impacts to key assets and operations. Developing an asset inventory and conducting a vulnerability and risk assessment are key steps in Olympia’s Sea Level Rise Response Plan, which will detail the Project Team’s planned actions to address SLR impacts to the downtown area and Port and LOTT facilities and operations. This report presents an overview of the adopted climate science and SLR scenarios used in the assessment; summarizes the data collection process and asset categories considered in the assessment; presents the vulnerability and risk assessment methodology and findings; and summarizes next steps in the SLR adaptation planning process. A vulnerability assessment is the process of identifying, quantifying, and prioritizing (or ranking) the vulnerabilities in a system. A risk assessment is the determination of quantitative or qualitative estimate of risk related to a well-defined situation and a recognized threat. Vulnerability refers to the inability (of a system or a unit) to withstand the effects of a hostile environment. A risk is the potential for loss, damage or destruction of an asset as a result of a threat exploiting a vulnerability. Risk is the intersection of assets, threats, and vulnerabilities. SLR and Water Level Scenarios The Project Team completed a Climate Science Review in October 2017. The climate science review indicated likely SLR of 7 inches by 2030, 13 inches by 2050, and 36 inches by 2100. High-range (unlikely but possible) SLR scenarios were identified as 13 inches by 2030, 25 inches by 2050, and 68 inches by 2100. The vulnerability and risk assessment included a detailed evaluation of 0, 6, 12, 18, and 24 inches of SLR. It also included a high level evaluation of a high-range end-of-century SLR scenario of 68 inches. The vulnerability and risk assessment evaluated the exposure of Olympia assets to coastal flooding as a result of king tides and the 100-year storm tide. King tide is a commonly used term to describe the highest astronomical tides that predictably occur a few times each year. For the purposes of this study, 12.5 feet NAVD88 was considered the elevation of a king tide. The 100-year storm tide is a severe, rarely occurring flood event that is a combination of a high astronomical tide and storm surge. The 100-year storm tide has a 1-percent chance of occurring in any given year. The Federal Emergency Management Agency (FEMA) flood insurance study for Thurston County identifies the 100-year storm tide elevation to be 14.1 feet NAVD88. Asset Data Inventory The Project Team collected information from the City, Port, and LOTT to identify assets for evaluation in the SLR vulnerability and risk assessment. The Project Team compiled asset data and collected qualitative information through questionnaires completed by City, State, Port, and LOTT staff. The Project Team identified individual assets (such as key buildings and facilities) for a more detailed evaluation and group assets (such as trees, stormwater outfalls, street lights, etc.) that may be vulnerable but are too numerous to evaluate on an individual basis. The Project Team invited public input on key downtown assets during a community workshop held on January 18, 2018. Olympia Sea Level Rise Vulnerability and Risk Assessment Page 2/46 March 2018 Vulnerability Assessment Approach The vulnerability assessment evaluated the exposure of the individual and group assets to projected flooding by king tides and the 100-year storm tide at each SLR scenario. This was done by overlaying the SLR inundation areas with each asset location to identify the timing and extent of exposure to flooding. Other aspects of vulnerability, including sensitivity and adaptive capacity, were considered in the assessment and documented by City, Port, and LOTT staff for critical assets in Attachment C to this report (Olympia Vulnerability and Risk Information). Vulnerability Profiles were developed to summarize the impacts of king tide (12.5 feet NAVD88) and 100-year storm tide (14.1 feet NAVD88) flooding at each SLR scenario (0, 6, 12, 18, 24, and 68-inch SLR). The profiles catalog the individual assets that are impacted at each SLR scenario under a future where no actions are taken to adapt to SLR. An inventory of SLR impacts to group assets was also compiled. This includes an inventory of the number of exposed assets within each group for each SLR scenario. The following potential impacts of flooding and SLR to LOTT’s Budd Inlet Treatment Plant were identified and evaluated at a high level: o High tides and storm surge in Budd Inlet could flood downtown Olympia and increase the volume of water conveyed to the Budd Inlet Treatment Plant by the combined sewer system. Flooding of 26 low-lying catch basins from a 100-year storm tide today could add 1.8 million gallons of stormwater to the combined sewer system during this event. With 6 inches of SLR, a 100-year storm tide could flood 153 catch basins, potentially adding 9.8 million gallons of stormwater to the combined sewer system during this event. o SLR will increase water levels in Budd Inlet and require more frequent pumping against higher water levels to discharge treated wastewater through LOTT’s marine outfalls. The effluent pump station capacity may experience a decrease of 1 million gallon per day (MGD) for each 3 feet of SLR. o Overland flooding of the Budd Inlet Treatment Plant may damage facilities and interrupt operations. Previous studies identified facilities that may be exposed to flooding by mid- century including the main utilidor, maintenance building, solids handling building, digesters, and the PSE Thurston substation. Low-lying inland areas may be exposed to backflow flooding through the stormwater system as a result of high tides, storm surge, and SLR. Potential areas of backflow flooding include the shoreline along Capitol Lake (between Sylvester and Columbia Streets and 4th and 7th Avenues), the Marine Terminal, and East Bay (vicinity of Adams Street and Thurston Avenue). Twenty-nine known contaminated sites were identified as vulnerable to flooding by a 100-year storm tide with 68-inches of SLR. Additional vulnerabilities were identified, but not evaluated in detail, including: o SLR will affect Capitol Lake dam operations and increase flood elevations within Capitol Lake. o SLR will affect the performance of the Indian/Moxlie Creek outfall and stormwater system. o SLR may increase the rate of shoreline erosion in existing hot spots and may expose new areas to erosion. Risk Assessment Approach For the assets identified as vulnerable to SLR, the Project Team considered the magnitude of the impact of flooding on the assets. This was done by considering the social, environmental and economic consequences of flooding for individual assets on a high level qualitative basis. Limited quantitative consequences were identified by the Project Team. Following the identification of consequences, a consequence rating of low, medium or high was applied by each agency for its individual assets. Olympia Sea Level Rise Vulnerability and Risk Assessment Page 3/46 March 2018 Risk Assessment Findings The following qualitative consequences of flooding were identified on a high level: o Commuter and social service disruptions. o Increased maintenance and repair costs. o Increased frequency of sewer bypass events. o Loss of access to facilities and services. o Increased capital costs. o Disruption of port operations and impacts to cargo. o Disruptions to commerce and employment. The following quantitative consequences of flooding were identified on a high level: o Flood fighting expenses of approximately $38,000 per event to address 12-inches SLR and a 100-year storm event of 9-hours in duration. o Single occupancy vehicle commuter delay costs of approximately $304,000 during a 24- inches SLR and a 100-year storm event. o Transit commuter delay costs of approximately $47,000 during a 24-inches SLR and a 100- year storm event. o Loss of 655 trees at an appraised value of $1,036,360 (by 36-inches SLR). Next Steps The findings of the vulnerability and risk assessment will be used to inform the development of potential adaptation strategies and identify priority areas for action. Olympia Sea Level Rise Vulnerability and Risk Assessment Page 4/46 March 2018 1. Introduction The City of Olympia (City), Port of Olympia (Port), and LOTT Clean Water Alliance (LOTT), collectively referred to as the Project Team, are developing a Sea Level Rise (SLR) Response Plan to address the anticipated impacts of SLR to Olympia’s Downtown area. This report presents the approach and results of a SLR vulnerability and risk assessment that was conducted to identify and evaluate Downtown Olympia’s vulnerability to, and risks resulting from, SLR. The vulnerability and risk assessment represents the second, third and fourth steps in the climate change adaptation planning process for Downtown Olympia and provides the basis for developing adaptation strategies. (Figure 1). Figure 1. Climate Change Adaptation Planning Framework The vulnerability and risk assessment is organized as follows: 1. Introduction 2. Climate Science and SLR Scenarios: a summary of the Olympia Climate Science Review and the SLR scenarios selected for evaluation in the vulnerability and risk assessment. 3. Asset Data Inventory: the data collection process and asset categories considered in the vulnerability and risk assessment. 4. Vulnerability Assessment Approach: an overview of the vulnerability assessment methodology for individual and group assets and development of SLR inundation maps. 5. Vulnerability Assessment Findings: vulnerability profiles that summarize the individual and group assets that are exposed to flooding at each SLR scenario.