Flooding, drainage and sea level rise
By Maurice Washington
Floods are increasingly affecting everyday life in Charleston and the surrounding areas with the imminent threat of worsened flooding in the future. In the next 18 years, Charleston will undergo six inches of sea level rise, with a projected 21 inches of storm surge. According to oceanic change experts, by 2045 Charleston will see more than 180 tidal floods annually. Under rising seas, an average high tide could inundate the historic district and flood low-lying neighborhoods as often as every other day.
Further, according to the South Carolina Department of Health and Environmental Control and the National Oceanic and Atmospheric Administration (NOAA), from the late 1950s through 2013, Charleston experienced a 409 percent increase in flooding, much of it from water periodically pooling during high tides. In addition, nuisance floods, often resulting from high tides on non-rainy days, hit Charleston an average of 23 days annually from 2007 to 2013. In 2015, the city had 38 days of flooding with a record number 50 days of flooding in 2016, largely due to higher tides.
The numbers cannot be fabricated nor can the consistent evidence be denied: Continuous flooding will eventually destroy our residential communities in the following ways:
Continued water damage will physically degrade thousands of residential structures, resulting in increased home maintenance expenses.
Continued homeowner claims will lead to increased insurance premiums and carriers will eventually stop writing coverage policies, as seen with past hurricane insurance coverage.
Vacated neighborhoods with multiple unoccupied residences will result in declining home values.
Regardless of their cause, floods have a profound effect on people, property and the economy. Unfortunately for the residents of Charleston, the issue of flooding cannot be entirely alleviated. Factors such as the geographical locale of Charleston as a flat area with an altitude of 13 feet above sea level, with some areas below sea level, exacerbates the threat and reality of tidal and torrential flooding. The long-term proposed strategy for flood mitigation will require a large amount of funding. Medium- and long-term funding solutions to include institutional and financial arrangements in a cross-administrative boundary situation will help to provide the funding to make feasible flooding solutions.
During the years, taxpayers have spent well more than $258 million to simply patch broken, outdated and overwhelmed drainage systems. Additionally, to protect Charleston from hazards caused by flooding, sea level rise and storm water runoff, former mayor Joe Riley initiated a number of project plans to address these adverse byproducts of flooding. Among the major drainage basins are the following: Calhoun West drainage, Lockwood Drive working shaft, Low Battery Seawall section, Spring/Fishburne Drainage Basin Improvement Phase 3, Church Creek Drainage Basin area, Windermere Drainage Basin area, Central Park Wambaw, Barberry Woods, Market Street Drainage Tunnel and Dupont/Wappoo Drainage Basin.
U.S. Highway 17 is a vital evacuation route, making the Spring-Fishburne drainage improvement project critical to the safety of residents. So, too, is the Calhoun West Drainage Basin project; this basin contains the hospital district (MUSC and Roper Hospital, which recently announced plans to move due to flooding issues), the College of Charleston and many businesses and residences directly impacted by frequent flooding. To avoid creating a potential bathtub in the Calhoun West Basin area and further exacerbate flood related damage, it is of paramount importance to advance actively this basin project simultaneously with the work at Low Battery Seawall and the Spring/Fishburne drainage basins projects.
Sacrifices must be made to solve the flooding problem of our city. Periodic street closures to complete infrastructure construction will be among the inconveniences that will serve the greater good. It will also require that those persons developing in Charleston not reap a handsome profit and leave citizens paying for the adverse environmental impact. It’s going to require city officials disciplining themselves to focus on core city services and leaving the construction of tourist attractions to the private sector. Those funds would then be available to help mitigate hazards such as flooding, drainage and sea level rise in Charleston’s neighborhoods and communities.
Also, between 2001 and 2006, 57 percent of developed land in Charleston County was in a FEMA floodplain. The more homes and people located in a floodplain the greater the potential for harm from flooding. It is time to say not no, but hell no to development in flood prone areas, filling wetlands and overdevelopment of Charleston and the surrounding areas, which continue to exacerbate flooding and stormwater runoff conditions.
Charleston municipal leaders must develop a more aggressive, comprehensive flooding and drainage long-range plan. To ensure the effectiveness of the plan, it must be scientifically engineered by a knowledge team of hydrologist and expert infrastructure specialists. Development and planning should involve citizen and stakeholder input, placing focus on the entire city, both big and small projects, that would help reduce our risk through proper mitigation planning. It should align with Charleston County regional hazard mitigation plans. In conjunction with flooding and drainage, the plan must also address issues and solutions for sea level rise, maintenance of current drainage systems and the protection and expansion of both wetlands and green spaces.
The city’s traditional solution to flood and drainage challenges has been gray infrastructure — such as pipe drainage systems, pump stations and tunnels, which are mainly single-objective oriented designs to cope with rainwater within the urban landscape. As the city of Chicago has learned, these drainage infrastructures often no longer have the capacity to keep pace with ongoing urbanization and the increasing rate of stormwater due to climate change and soil sealing. Additionally, they can lead to increased runoff and a higher risk of urban flooding. Furthermore, managing storm water runoff through gray infrastructure approaches typically entails high construction, maintenance and repair costs. Although gray approaches have certainly reduced the damages incurred from flooding events and are arguably still necessary for extreme flood events, pursuing alternative approaches that accomplish these aims while offering potential additional benefits for the future should be considered moving forward. Using nature-based solutions such as rain gardens, constructed wetlands, permeable pavement, detention ponds, investing in urban green spaces and other adaptations to reduce runoffs are among other proven ways to alleviate flooding. In many cases, combining green and gray infrastructure measures into so-called hybrid solutions may have the best potential to naturally capture, slow down and filter stormwater. Careful analysis should be conducted to evaluate the range of available options and design flood management schemes that combine nature and gray infrastructure.
To balance effectively all the competing interests and coastal resources in the face of climate threats, we will need flexibility and robust land-use regulations. Zoning is the most powerful tool local government has to preemptively mitigate hazards. Through planning and zoning, local governments can determine what is at risk, what is safe to build and where it is safe to build. By analyzing vulnerabilities and planning for the impacts, local governments can shape land owners’ expectations and build political support for adaptive measures that would help mitigate flooding, drainage, and sea level rise in the Charleston area.
Maurice Washington is chairman of the Charleston County Republican Party and former Charleston City Council member. He is president CEO of Trust Management, LLC, and is committed to a life of public service.
