MassDEP Proposes New Coastal Floodplain Standards to Improve Climate Resiliency

There has been a joke for some time now that whenever MassDEP proposes new regulations, they must have finally developed the performance standard for Land Subject to Coastal Storm Flowage (“LSCSF”). Well, the joke’s on us, folks: they’ve gone and done it.

The long-awaited LSCSF performance standard is just one of several proposed revisions to MassDEP’s Wetlands Protection Regulations (310 CMR 10.00) that, in conjunction with proposed revisions to the Waterways Regulations (310 CMR 9.00) and the Water Quality Certification (WQC) Regulations (314 CMR 9.00), are intended to improve the Commonwealth’s resilience to the impacts of climate change. The proposed wetlands regulations aim to promote coastal resiliency against the worsening impacts of storms, flooding, and rising sea levels caused by climate change. The proposal also contains significant updates to MassDEP’s stormwater management standards to promote resiliency against increased flooding and storm damage.

If promulgated, the proposed regulations will significantly impact development in the coastal floodplain throughout Massachusetts. LSCSF is the area of shoreline with a 1% annual chance of flooding in a coastal storm (based on FEMA Flood Insurance Rate Maps). It is significant to storm damage prevention and flood control (interests protected by the Wetlands Protection Act, G.L. c. 131, § 40) because it diminishes and buffers the high energy effects of storm waves.

The proposed regulations identify five critical characteristics of LSCSF that are significant to the protection of the storm damage prevention and flood control interests:

• The ability of LSCSF to dissipate wave energy and to decrease the velocity of moving water;
• The ability of LSCSF to receive coastal flood waters that spread laterally and landward and percolate downward into the soil and sediment;
• The ability of LSCSF to allow flood water to flow across the landform without redirecting or channeling flow or increasing the velocity of the flood waters;
• The ability of the vegetative cover in LSCSF to slow moving water, thereby reducing erosion and sedimentation; and
• The ability of LSCSF to store flood waters that are confined by a natural or manmade feature (e.g., a seawall, culvert, bridge, dike, bulkhead, revetment, or topographic depression) until such time as it can slowly return to the ocean or infiltrate into the ground.

Performance standards in the Wetlands Protection regulations are intended to guide local conservation commissions in reviewing development projects in wetland resource areas. The proposed LSCSF performance standards cover new development (proposed 310 CMR 10.36(5)-(7)) and redevelopment within LSCSF (proposed 310 CMR 10.36(8)). The first two performance standards focus on the areas where wave action is the strongest and prohibit activities that can adversely affect the five critical LSCSF characteristics. Most significantly, the proposed regulations would prohibit any new building construction in the zone with the strongest wave action, which has the highest risk of storm damage. They would permit new building construction in the mid-range wave action zone only if elevated on open piles and located as far landward as possible, with a driveway of crushed stone or shells and without curbing or walls. The third performance standard would require that any activity in the lowest wave action zone implement state-of-the-art design and construction standards to minimize any impact on the critical LSCSF characteristics.

The fourth performance standard would allow redevelopment within previously developed areas of LSCSF as long as the redevelopment improves resiliency over existing conditions. Developed areas are proposed to include those with existing structures, fill or other vertical impediments to flow, construction debris, and pavement. Existing conditions may be improved by topographical alterations to provide flood storage, planting vegetation, reducing impervious surfaces, increasing permeability, removing vertical impediments to flow, and restoring or creating coastal resource areas. No new buildings would be allowed in the highest wave action zone, and reconstructed buildings in this zone would need to be elevated on open piles. No reconstructed buildings would be allowed to expand their footprint in any LSCSF zone. Alterations to structures in the mid- and low-range wave action zone would need to incorporate a minimum of two feet of additional elevation above the 1% base flood elevation. Historic structures are exempt from these requirements.

Overall, the proposed performance standards reflect a serious and thoughtful approach to managing development in a long-overlooked resource area. Development in the coastal floodplain has often proceeded with scant review due to the lack of a guiding framework, a missed opportunity given that the resource area is often at the interface of climate impacts. These proposed regulations will guide careful review of potentially highly exposed development and, in some cases, promote managed retreat in the face of climate uncertainty. In practice, they appear similar to the Riverfront Area redevelopment performance standard in 310 CMR 10.58(5), but may prove immensely more workable for conservation commissioners as they are more streamlined and include clear directives on what is and is not allowed in specific areas.

There is much more to the proposed regulations than just the LSCSF performance standards. MassDEP is accepting public comments on the proposed regulations until March 1, 2024. Follow us as we dig deeper into the other provisions of the proposed regulations, and contact us if you need guidance on what these regulations could mean for your project.