Weston & Sampson Developing an Effective Flood Reduction Program for the City of Charleston (West Ashley), South Carolina

The West Ashley section of Charleston, South Carolina has seen significant growth since it was first developed in the 1950s, now accounting for almost half of the city’s 120,000+ residents. Over the years, the 10,000-acre basin it sits in has seen increased flooding during severe storms and hurricanes. During the last decade, the city had commissioned several studies and implemented a few projects to make improvements, but none addressed flood prevention in the entire basin. In a more aggressive effort to fight this repetitive flooding, they retained a team led by Weston & Sampson to work with them to develop a plan and make recommendations to reduce flooding in the entire Church Creek basin of West Ashley.

Our team included internationally recognized engineers, the National Oceanic and Atmospheric Administration (NOAA), and our own local flooding and hydrology experts who worked together to develop a suitable flood prevention plan for the Church Creek Basin. We began by coming up with a practical approach to conducting a field investigation to gather the information that such a critical project required. One of the main questions we had to answer right away was, is the existing hydraulic model for the area still accurate? Does it reflect current physical and climate conditions? Based on our field inspections of stormwater management assets in the area, we found that aspects of the model needed updating. Then, when Tropical Storm Irma came through, we seized the opportunity to deploy a field team to take measurements both during and after the storm. This helped us update the model from one-dimensional to two. Based on our team’s collective experience, we also tested additional improvements to the model to help develop an effective flood reduction plan.

Our team’s resulting plan included seven separate but related initiatives – six of these involved actual stormwater management projects and one was to update the city’s stormwater design policies to protect storage capacity brought about by the projects.

The city has already begun implementing our recommendations. We assisted the city by updating the city’s stormwater policy manual and are designing several stormwater diversion and storage projects to help reduce flooding in West Ashley. In fact, the city has already deemed our team’s work so promising and effective that they presented us with a replica gold coin of appreciation at a public City Council meeting. The original $100 gold coin had been offered up by the city’s Mayor in the late 19^th century to anybody who could develop an effective flood control plan. It had gone unclaimed until now.

Original Press Release