Sea Level Rise and Infrastructure Vulnerability - Beaufort SC
This project focused on identifying the potential infrastructure problems that will exist as sea level rise (SLR) occurs and determining how those effects can be minimized or mitigated to ensure that the needs of both the local communities and the military facilities are accommodated. This is particularly significant in the Beaufort area due to the fact that water and sewer services are provided to the military facilities by the same regional provider that serves the local communities; local roads, highways and bridges provide the only access to MCAS Beaufort and MCRD Parris Island.
As a part of the overall vision, this project’s goals were to document the vulnerability of infrastructure that supports the MCAS Beaufort and MCRD Parris Island bases (i.e., is critical to the goal); and provide avenues and costs associated with mitigating the effects of SLR within the greater Northern Beaufort area in the future. A systematic scheme was developed to highlight vulnerable and critical infrastructure. The three screens represent 1) the exposure risk – what is the risk that the infrastructure will be ‘wet’ during monthly high tides; 2) the sensitivity of the infrastructure to being ‘wet’ once a month (on average); and 3) the importance of that infrastructure to goals of the project. The screen thresholds (i.e., what is let through) can be tuned depending on the input from citizens, officials, scientists, engineers, etc.
Screening for Vulnerable and Critical Infrastructure
For each of the above factors, unique “screening” values (1 to 3, based on low, medium, high scores) were computed for each piece of infrastructure based on its location, elevation, type of infrastructure, and the projections of potential sea level increases. Separate values were assigned based on future sea level projections for 2020, 2030, 2040, 2060, and 2085. By setting the threshold for each screen in the funnel scheme based on the input of the stakeholders the infrastructure passing through all three screens would be considered both vulnerable and critical. This is the infrastructure that should be given priority for mitigation strategies and costs developed for these strategies also represent a good estimate for resiliency planning.
As a starting point for identifying at-risk infrastructure, we choose a moderate to high level of vulnerability (exposure risk + sensitivity risk = 5 or more) coupled with a criticality screening based on proximity to the bases, evacuation routes, and the social vulnerability within the area. In this baseline 2040 planning scenario, the amount of infrastructure in the study that was vulnerable and critical is on the order of 4% in 2040. Transportation assets (roads and highways) is at the high end of this range and the percent of vulnerable transportation assets increase more rapidly through time than the other types – water utilities and storm water.
"Sunny Day" flooding in the Lowcountry of SC
Infrastructure costs were determined on a per-unit basis using a preliminary engineering analysis of the asset types and a single recommended strategy – either relocate, raise, or protect in place – to minimize risk. There were thousands of miles of transportation networks, thousands of miles of pipes, and thousands of individual assets (drains, hydrants, lift-stations, etc). Total costs for the specific resiliency planning targets (screen values) were computed using the unit costs developed for each asset type and its recommended mitigation strategy.
This project outlined a logic and technical approach for using science and engineering to assign infrastructure vulnerability; and introduced the topic of criticality with respect to a specific goal. To bring the these separate measures of prioritization together, a logic framework was developed to assess the mitigation needs and the costs of the effort for planning purposes to ensure the continued operation of the bases and the way of life in these Lowcountry communities.
A very important aspect that cannot be captured at the broad scale of this preliminary project is the interdependence of the infrastructure. Retrofitting one piece of infrastructure can have gains across several different infrastructure assets. The corollary applies as well in that investing in one asset may not solve the problem, and will require multiple investments in other infrastructure for the system to be resilient. This type of a system approach/understanding is the next step in the process. And in this regard, one of the main recommendations is that separate agencies, commissions, and service providers should tackle these potential issues as a team to maximize systematic gains.