Charleston County committee adopts recommendations after review of multi-hazard vulnerability assessment

The Charleston County Resilience and Sustainability Advisory Committee heard a presentation on the county's multi-hazard vulnerability assessment and tools and voted to recommend staff explore a local resilience fund and to encourage formation of an interdepartmental working group to advance resilience strategies.

The assessment, completed in October 2024, uses parcel-level data and nine modeled flooding scenarios to show where flood exposure, adaptive capacity and critical infrastructure overlap. Tim (Fernleaf consultant) and Steven Jilka (Fernleaf) described an interactive mapping tool and a set of 11 strategies county staff identified for implementation.

The assessment matters because it moves the county from broad statements of risk to spatially specific priorities that can inform funding, grant applications and project sequencing. Molly (county staff) framed the committee's choices as a short list of near-term actions that would help the county take advantage of limited federal and state mitigation funding and develop local, sustained capacity.

Fernleaf's presenters said the assessment rests on three features: parcel-level vulnerability scoring, aggregation to planning areas, and an interactive web tool to test project boundaries and compare before-and-after scenarios. According to the presentation, the assessment:

- Modeled nine different flood scenarios to capture risks that FEMA flood insurance rate maps do not always show, including tidal and fluvial flooding and future sea-level rise; - Aggregated parcel-level analysis into 15 county planning areas to help prioritize interventions; and - Produced 11 strategies with associated actions that county staff and partners endorsed as priorities for implementation.

"We want to avoid any type of hazard that causes enough loss in functional capacity that there's a tipping point that we cannot get back to the pre-hazard functionality," Tim said, describing the assessment's resilience objective.

The committee saw examples of the tool's application. Presenters showed a before-and-after comparison in a tested location where installing check valves and targeted drainage work reduced vulnerability for several parcels and community facilities. Fernleaf also described a pilot funded under the Climate Smart Communities Initiative to develop a prioritization framework for flood mitigation and a brownfields redevelopment strategy; results from those pilots are expected in a few months.

Presenters and committee members emphasized the need to pair data with funding and governance. The assessment identified concentrated areas where high flood vulnerability overlaps with low flood-insurance coverage and high social vulnerability; staff cited a case in which the intersection of those three factors narrowed to three census block groups for initial prioritization. Fernleaf said roughly 14% of identified critical facilities were rated highly vulnerable in a modeled 20-year flood event in the county.

Committee members raised implementation questions: how to measure return on investment, how to maintain infrastructure (for example, check valves), how to align county and municipal plans, and how to track progress. Presenters said an existing recording and training on the interactive tool (ExcelAdapt) can be made available to staff and partners to support ongoing use.

After discussion, committee members moved and seconded a recommendation for staff to explore a local resilience fund to generate a stable pipeline of prioritized projects and reduce dependence on one-off grants. The committee voted by voice; the motion passed. Committee members also supported creating an interdepartmental working group to coordinate resilience work across county departments and with municipalities and partners.

Committee members and staff identified immediate next steps: continue the Climate Smart Communities pilot work (prioritization framework and brownfields strategy), make the ExcelAdapt training available to county staff, pursue aligned grant applications using the assessment's data, and return to the committee with metrics and a proposed structure for the resilience fund and governance approach.

The committee's work builds on existing county planning efforts, the National Flood Insurance Program and FEMA tools, and aims to provide a consistent data-driven basis for flood mitigation, heat resilience, easement planning, and brownfield redevelopment. Fernleaf and county staff said they will present pilot deliverables and refined recommendations to the committee when available.