Buffers increase resilience to flooding, among other benefits

Forested wetland and riparian buffers are nature’s workhorse. These vegetated zones lie between developed land and our wetlands and waterways, providing many benefits to our society. As a member of the Sussex County Wetlands and Buffers Working Group, I participated in over a dozen meetings to develop a framework for the proposed buffer ordinance. As a coastal hazards specialist with Delaware Sea Grant, I help communities assess risks from climate and weather hazards, and identify strategies to improve local resilience. With this article, I would like to contribute science-based information to the public discourse ahead of Sussex County’s hearing on the proposed ordinance Tuesday, Feb. 22. 

Sussex County’s low mean elevation and proximity to tidal waters contributes to a higher-than–average risk of coastal flooding. According to FEMA, nearly a quarter of all properties in Sussex County have a 26 percent chance of being flooded at least once over the next 30 years. Our tides are getting higher and our land is subsiding, placing Delaware within a hotspot for sea-level rise (Delaware Geological Survey). The National Oceanic and Atmospheric Administration has observed a doubling of high tide flooding over the past 20 years at its Lewes tide gauge and projects that the number of those floods will double again by 2030, resulting in 15 to 30 days of flooding per year (2021 State of High Tide Flooding and Annual Outlook). 

Sussex County is also at greater risk of inland flooding. Due to the warming of our planet, mean annual precipitation has increased 3.6 inches since 1895 (Office of the State Climatologist for Delaware). The Delaware Climate Change Impact Assessment indicates that heavy rainfall events will become more intense and frequent. All new development in Sussex County must adhere to stormwater management regulations, but they are often based on current conditions that do not factor in sea-level rise or greater precipitation intensity. Unless higher standards are followed, new development in Sussex County may not be resilient to future flooding.  

Flooding itself does not cause property damage or harm. Flooding is a natural process that maintains the physical structure and biological diversity of the floodplain ecosystem. But where we build and how we design our communities directly influence our exposure and vulnerability to flooding. 

In Sussex County, we are experiencing unprecedented development. Revenue from realty transfer taxes is anticipated to hit a record $36.9 million this year. A 2019 report from Climate Central and Zillow found Delaware is twice as likely to build in risk zones subject to 10-year floods and sea-level rise as compared to lower-risk zones (Ocean at the Door: New Homes and the Rising Sea, 2019). That report ranked Sussex County third among all coastal counties in the United States regarding the number of new homes built in risky locations (through 2017). These practices run counter to best practices defined by the American Planning Association and the Association of State Floodplain Managers, which discourage new development in the floodplain and promote the use of natural infrastructure like open space, buffers, forests, farms and wetlands. 

Why are buffers a necessary form of “green” infrastructure? Development in the floodplain often manipulates the natural conveyance of water to keep it away from people and property. This sometimes disrupts the natural functions of the floodplain involving sediment transport, water flows, water levels and ecology. Wetland and riparian buffers provide room for banks to flood, migrate and adapt to changing conditions. They lower flood velocities and flood peaks, stabilize soils, and reduce wind and wave action. They protect property values and lives. Buffers intercept pollutants and sediment from surface water runoff, thereby protecting our water quality and drinking water. They provide critical breeding and feeding grounds for wildlife, and contribute to the aesthetic value of our communities. 

Buffers are most effective when left intact and allowed to perform all of their natural functions. Spacious buffer widths lessen people and property’s exposure to flooding by providing more room to slow runoff and for floodwaters to overtop banks safely. As sea level advances, wetlands will need room to migrate landward—as they do naturally—or they risk converting to open water. Insufficient buffer widths may not accommodate wetland migration or other needed adaptations to changing conditions. Forested buffers are preferred to non-forested buffers because their vegetation and root structure enhance flood protection and soil stability. Forested buffers also capture pollutants effectively and provide habitat for wildlife. 

Sussex County prides itself on taking care of its own. Because of their multiple benefits, buffers are an effective investment in the future resilience of our county. If we design and maintain buffers to their full potential, we are protecting the well-being of our future generations.