Sea Level Rise

Harnessing Green Infrastructure in Charleston, SC: Stormwater Management and Flood Resilience through Rain Gardens, Bioswales, and Permeable Pavements

Executive Summary: Charleston, SC, is increasingly vulnerable to the impacts of climate change, including sea level rise and increased frequency and intensity of storms. In response, the city must prioritize innovative and sustainable strategies to manage stormwater runoff and enhance its natural defenses against flooding. This white paper explores the benefits and implementation of green infrastructure in Charleston, focusing on rain gardens, bioswales, and permeable pavements as effective stormwater management solutions that can help build a more resilient and sustainable city.

1. Introduction:
   • 1.1. Background on Charleston’s climate vulnerabilities: Charleston, South Carolina, a historic coastal city, is experiencing the compounding effects of climate change, including sea level rise, increased storm frequency, and intensified precipitation events. The city’s low-lying topography, coupled with its extensive coastline, makes it particularly vulnerable to flooding from storm surges, heavy rainfall, and high tides. These challenges are exacerbated by the ongoing urban development and land use changes, which can alter the natural drainage patterns and increase the volume of stormwater runoff. Addressing these vulnerabilities is crucial to ensure the safety, health, and prosperity of Charleston’s residents, businesses, and natural ecosystems.
   • 1.2. Importance of stormwater management in the context of climate change: Effective stormwater management is critical for mitigating the impacts of flooding and reducing the risk of property damage, infrastructure failure, and environmental degradation in Charleston. Traditional stormwater management techniques often involve the use of grey infrastructure, such as concrete channels, pipes, and detention basins, which primarily focus on collecting and conveying runoff away from developed areas. While these systems may provide short-term relief, they can contribute to long-term problems, such as increased flood risk downstream, reduced groundwater recharge, and impaired water quality. In the context of climate change, it is essential to explore innovative and sustainable stormwater management strategies that not only address the immediate risks of flooding but also promote long-term resilience and environmental stewardship. Green infrastructure offers a promising alternative, as it harnesses natural processes to absorb, filter, and store stormwater, while providing a range of additional ecological, social, and economic benefits.
   • 1.3. Overview of green infrastructure as a sustainable solution: Green infrastructure is an approach to stormwater management that utilizes vegetation, soils, and other natural elements to mimic the natural hydrological processes of infiltration, evapotranspiration, and storage. By integrating these systems into the urban landscape, green infrastructure can help to reduce the volume and velocity of stormwater runoff, improve water quality, recharge groundwater, and enhance the city’s overall resilience to flooding. This white paper focuses on three key green infrastructure components – rain gardens, bioswales, and permeable pavements – as effective stormwater management solutions for Charleston. The following sections will provide an in-depth analysis of each component, exploring their functions, benefits, and design principles, along with recommendations for their successful implementation in the city. By harnessing the potential of green infrastructure, Charleston can build a more resilient, sustainable, and vibrant urban environment in the face of a changing climate.
2. Green Infrastructure Components:
   • 2.1. Rain gardens
   • 2.1.1. Definition and function: Rain gardens are shallow, landscaped depressions designed to capture, store, and infiltrate stormwater runoff from impervious surfaces such as rooftops, driveways, and parking lots. Planted with native vegetation that can tolerate both wet and dry conditions, rain gardens slow down runoff, promote infiltration, and provide habitat for local wildlife. By filtering pollutants and reducing the volume of stormwater entering Charleston’s drainage system, rain gardens can help alleviate the burden on traditional stormwater infrastructure and improve water quality in local waterways.
   • 2.1.2. Benefits for stormwater management and flood resilience: Rain gardens provide numerous benefits for stormwater management and flood resilience in Charleston, including:
     • Reducing the volume and peak flow rates of stormwater runoff
     • Increasing groundwater recharge and maintaining base flows in streams
     • Improving water quality by filtering out pollutants and sediments
     • Providing habitat for local flora and fauna, enhancing urban biodiversity
     • Contributing to the aesthetic appeal and overall livability of the city
   • 2.1.3. Design principles and implementation in Charleston: To effectively implement rain gardens in Charleston, several design principles should be considered:
     • Select appropriate sites with suitable infiltration rates and sufficient space to accommodate the desired size and capacity of the rain garden
     • Choose native plant species adapted to local climate conditions, with a preference for those that can tolerate both wet and dry periods
     • Ensure proper grading to direct stormwater runoff into the rain garden and prevent erosion or ponding
     • Plan for regular maintenance, including weeding, pruning, and trash removal, to ensure the long-term performance and aesthetic appeal of the rain garden
   • 2.2. Bioswales
     • 2.2.1. Definition and function: Bioswales are linear, vegetated channels designed to convey, filter, and infiltrate stormwater runoff while reducing flow velocity. They are typically installed along roadways, parking lots, or other impervious surfaces to capture and treat runoff before it enters the stormwater drainage system. Similar to rain gardens, bioswales are planted with native vegetation and can incorporate features such as check dams or berms to slow down and distribute stormwater more evenly.
     • 2.2.2. Benefits for stormwater management and flood resilience: Bioswales offer multiple benefits for stormwater management and flood resilience in Charleston, including:
       • Reducing peak flow rates and preventing erosion by slowing down stormwater runoff
       • Enhancing water quality by filtering out pollutants, sediments, and debris
       • Increasing groundwater recharge through infiltration
       • Providing habitat for native plants and wildlife, supporting urban biodiversity
       • Serving as a visually appealing, low-maintenance landscaping feature
     • 2.2.3. Key design principles for successful bioswale implementation in Charleston include:
       • Select suitable locations with adequate space, proper slope, and appropriate soil conditions for infiltration
       • Design bioswales with gentle slopes and incorporate check dams or berms to slow down stormwater and encourage infiltration
       • Use native plant species adapted to local conditions, with a mix of grasses, sedges, shrubs, and trees to create diverse and resilient vegetation
       • Establish a maintenance plan to ensure long-term functionality, including periodic inspections, sediment removal, and vegetation management
   • 2.3. Permeable pavements
     • 2.3.1. Definition and function: Permeable pavements are alternative paving materials that allow water to infiltrate through their surface and into the underlying layers, reducing stormwater runoff and promoting groundwater recharge. Common types of permeable pavements include porous asphalt, pervious concrete, and permeable interlocking pavers. These systems are typically used for low traffic areas such as sidewalks, driveways, parking lots, and pedestrian plazas. By replacing traditional impervious surfaces, permeable pavements can help mitigate the effects of urbanization on the hydrological cycle and reduce the strain on Charleston’s stormwater infrastructure.
     • 2.3.2. Benefits for stormwater management and flood resilience: Permeable pavements provide several benefits for stormwater management and flood resilience in Charleston, including:
       • Reducing the volume and peak flow rates of stormwater runoff by promoting infiltration
       • Improving water quality by filtering pollutants and sediments through the pavement’s porous structure
       • Replenishing groundwater resources and maintaining base flows in local waterways
       • Reducing the urban heat island effect by allowing water to evaporate from the pavement surface, cooling the surrounding air
       • Providing a durable, low-maintenance alternative to traditional paving materials
     • 2.3.3. Design principles and implementation in Charleston: To effectively implement permeable pavements in Charleston, several design principles should be considered:
       • Select appropriate locations with suitable soil conditions and infiltration rates, and avoid areas with high groundwater tables or potential contamination risks
       • Ensure proper design and construction, including adequate sub-base preparation, to support the anticipated loads and provide sufficient storage capacity for infiltrated water
       • Implement regular maintenance practices, such as vacuum sweeping or pressure washing, to prevent clogging and maintain the permeability of the pavement surface
       • Consider using permeable pavements in conjunction with other green infrastructure practices, such as rain gardens or bioswales, to create a comprehensive stormwater management strategy
   • By incorporating rain gardens, bioswales, and permeable pavements into Charleston’s urban landscape, the city can enhance its stormwater management capabilities, improve water quality, and increase its resilience to flooding events. These green infrastructure components offer a sustainable, cost-effective, and visually appealing solution to the challenges posed by climate change, providing a solid foundation for a more resilient and vibrant Charleston.
3. Case Studies:
   • 3.1. Examples of successful green infrastructure projects in Charleston:
     • 3.1.1. The Charleston Medical District Green Infrastructure Project: This collaborative initiative between the Medical University of South Carolina, Roper St. Francis Healthcare, and the Ralph H. Johnson VA Medical Center aimed to retrofit existing streetscapes and parking lots with green infrastructure practices. Rain gardens, permeable pavements, and bioswales were installed throughout the district to manage stormwater runoff, reduce localized flooding, and improve water quality. This project not only enhanced the district’s resilience to flooding but also transformed the streetscape into a more inviting, walkable, and aesthetically pleasing environment.
     • 3.1.2. The East Bay Street Bioswale Project: To address frequent flooding and poor water quality in the vicinity of East Bay Street, the City of Charleston implemented a bioswale project along a section of the street. The bioswale captures and filters stormwater runoff from the roadway and adjacent properties, reducing the burden on the existing stormwater infrastructure and minimizing flooding risks. This project demonstrates the effectiveness of green infrastructure in an urban setting, with the added benefit of creating a visually appealing streetscape that enhances the neighborhood’s overall livability.
     • 3.1.3. The Mitchell Elementary School Rain Garden: In collaboration with local partners, Mitchell Elementary School installed a rain garden on its campus to manage stormwater runoff from the school building and surrounding impervious surfaces. This project not only provided an effective stormwater management solution but also served as an educational tool for students, fostering a deeper understanding of sustainable practices and environmental stewardship.
   • 3.2. Lessons learned and best practices for implementation:
     • Collaboration and stakeholder engagement: Engaging key stakeholders, including city agencies, property owners, community members, and local organizations, is crucial for the successful planning, design, and implementation of green infrastructure projects.
     • Integration with existing infrastructure: Green infrastructure practices should be designed to complement and enhance existing stormwater infrastructure, ensuring that they function effectively in conjunction with traditional systems.
     • Flexible and adaptable design: Green infrastructure components should be designed to accommodate site-specific conditions and constraints, with the flexibility to adapt to changing environmental and urban contexts.
     • Education and outreach: Incorporating educational components into green infrastructure projects can help raise public awareness about the benefits of these practices and encourage broader adoption throughout the city.
     • By learning from these case studies and following best practices, Charleston can continue to expand its green infrastructure network, building a more resilient and sustainable urban environment in the face of climate change.
4. Financing and Incentives:
   • 4.1. Funding opportunities for green infrastructure projects in Charleston
     • City budget allocations: Allocate a portion of the city budget specifically for green infrastructure projects, ensuring consistent funding for planning, design, construction, and maintenance.
     • Grants and external funding: Pursue grants and external funding from state and federal agencies, non-profit organizations, and private foundations that support green infrastructure and environmental conservation projects.
     • Public-private partnerships (PPPs): Engage in partnerships with private entities to share the costs and benefits of implementing green infrastructure projects on public and private properties.
     • Stormwater utility fees: Consider establishing a stormwater utility fee that charges property owners based on their contribution to stormwater runoff. The revenue generated can be used to fund green infrastructure projects and incentivize property owners to implement on-site stormwater management practices.
   • 4.2. Local, state, and federal incentives for green infrastructure implementation
   • Local incentives:
     • Expedited permitting: Offer streamlined permitting processes for projects that incorporate green infrastructure, reducing the time and cost associated with obtaining necessary approvals.
     • Property tax reductions or rebates: Provide property tax reductions or rebates for property owners who implement green infrastructure practices on their properties, encouraging private sector investment in sustainable stormwater management.
   • State incentives:
     • Tax credits: Offer state tax credits for developers and property owners who incorporate green infrastructure into their projects, promoting wider adoption across the state.
     • Low-interest loans: Establish a low-interest loan program for green infrastructure projects, enabling property owners and developers to finance the upfront costs of implementation.
   • Federal incentives:
     • Clean Water State Revolving Fund (CWSRF): Utilize the CWSRF program, administered by the Environmental Protection Agency (EPA), which provides low-interest loans for water quality improvement projects, including green infrastructure.
     • Federal grant programs: Apply for federal grants, such as those offered by the EPA, the Department of Transportation (DOT), and the National Oceanic and Atmospheric Administration (NOAA), that support green infrastructure and climate resilience projects.
   • By exploring various financing mechanisms and leveraging incentives at multiple levels of government, Charleston can mobilize the necessary resources to support the widespread implementation of green infrastructure, enhancing the city’s resilience to flooding and other climate-related challenges.
5. Regulatory and Policy Framework:
   • 5.1. Existing regulations and policies supporting green infrastructure in Charleston:
     • Charleston has already taken steps to incorporate green infrastructure into its regulatory and policy framework. Some key examples include:
     • Stormwater Design Standards Manual: Charleston’s Stormwater Design Standards Manual provides guidelines for stormwater management, including the use of green infrastructure practices such as rain gardens, bioswales, and permeable pavements to manage runoff and improve water quality.
     • Comprehensive Plan: The city’s Comprehensive Plan recognizes the importance of green infrastructure in addressing stormwater management and climate resilience, and includes goals and strategies related to the implementation of green infrastructure practices.
     • Floodplain Management Ordinance: Charleston’s Floodplain Management Ordinance establishes regulations for development in flood-prone areas, encouraging the use of green infrastructure to reduce flood risks and protect water quality.
   • 5.2. Recommendations for enhancing policy support and integration of green infrastructure in city planning:
     • To further strengthen the regulatory and policy framework supporting green infrastructure in Charleston, several recommendations can be considered:
     • Develop a comprehensive green infrastructure policy: Create a standalone policy or integrate green infrastructure principles into existing policies, such as zoning codes, building codes, and landscape regulations, to ensure a cohesive approach to implementing and maintaining green infrastructure throughout the city.
     • Establish green infrastructure design guidelines: Develop a set of design guidelines that provide clear and consistent standards for green infrastructure practices, ensuring that projects are designed and constructed in a manner that maximizes their effectiveness and resilience.
     • Integrate green infrastructure into climate resilience planning: Incorporate green infrastructure strategies into the city’s climate resilience plans, recognizing the role of these practices in mitigating the impacts of climate change, particularly in relation to sea-level rise and flooding.
     • Promote cross-departmental collaboration: Encourage coordination and collaboration among city departments and agencies involved in green infrastructure planning, design, implementation, and maintenance, ensuring a consistent and integrated approach to managing stormwater and enhancing climate resilience.
     • Engage community stakeholders: Foster ongoing dialogue and collaboration with community stakeholders, including residents, businesses, and local organizations, to raise awareness about the benefits of green infrastructure and to solicit input and feedback on green infrastructure projects.
   • By enhancing the policy support and integration of green infrastructure in city planning, Charleston can create a more comprehensive and effective framework for addressing stormwater management challenges and improving the city’s resilience to climate change.
6. Community Engagement and Education:
   • 6.1. Importance of community involvement in green infrastructure projects:
     • Community involvement is a critical component of successful green infrastructure implementation. Engaging local residents, businesses, and organizations in the planning, design, and maintenance of green infrastructure projects can yield several benefits, including:
     • Enhanced public support: Involving the community in the decision-making process can foster a sense of ownership and support for green infrastructure projects, ensuring their long-term success and sustainability.
     • Improved project outcomes: Collaborating with community members can provide valuable local knowledge and insights, helping to identify potential issues and opportunities and resulting in better-designed projects that are more responsive to local needs and preferences.
     • Increased environmental stewardship: Engaging the community in green infrastructure initiatives can raise awareness about the importance of sustainable stormwater management and climate resilience, encouraging broader adoption of these practices and fostering a culture of environmental stewardship.
   • 6.2. Strategies for promoting public awareness and participation in Charleston:
     • Public workshops and meetings: Organize public workshops, meetings, and other events to provide information about green infrastructure projects, solicit input and feedback from community members, and identify local priorities and concerns.
     • Educational programs and resources: Develop educational programs and resources, such as brochures, fact sheets, and online materials, to inform residents and businesses about the benefits of green infrastructure and provide guidance on implementing these practices on private properties.
     • Demonstration projects: Implement highly visible, well-designed green infrastructure demonstration projects that showcase the aesthetic and functional benefits of these practices, serving as examples of what can be achieved through community-wide adoption.
     • Partnerships with local organizations: Collaborate with local non-profits, schools, businesses, and other organizations to leverage their expertise and networks in promoting green infrastructure and engaging the community in related initiatives.
     • Volunteer opportunities: Provide opportunities for community members to get involved in green infrastructure projects, such as planting and maintaining rain gardens, participating in neighborhood clean-ups, or monitoring the performance of green infrastructure installations.
   • By actively engaging the community in green infrastructure projects and promoting public awareness of the benefits of these practices, Charleston can foster a sense of shared responsibility and commitment to creating a more resilient and sustainable city in the face of climate change.
7. Conclusion:
   • 7.1. Summary of key findings:
     • This white paper has highlighted the importance of implementing green infrastructure practices, such as rain gardens, bioswales, and permeable pavements, in Charleston, SC, as a means of addressing the city’s stormwater management challenges and enhancing its resilience to climate change. Through a review of existing projects, best practices, and policy recommendations, the paper has demonstrated the potential of green infrastructure to provide cost-effective, sustainable, and visually appealing solutions that contribute to a more resilient and vibrant urban environment.
   • 7.2. The potential of green infrastructure in building a more resilient and sustainable Charleston:
     • By adopting and investing in green infrastructure solutions, Charleston can reap numerous benefits, including:
     • Improved stormwater management: Green infrastructure practices can help to reduce the volume and peak flow rates of stormwater runoff, alleviating pressure on the city’s existing infrastructure and reducing the risk of flooding.
     • Enhanced water quality: Green infrastructure can contribute to improved water quality by filtering pollutants and sediments from stormwater runoff before it enters local waterways.
     • Increased climate resilience: Green infrastructure can play a crucial role in helping Charleston adapt to the impacts of climate change, particularly sea level rise and more frequent and intense precipitation events.
     • Aesthetic and social benefits: Green infrastructure can enhance the visual appeal of urban areas, contributing to more attractive and livable communities.
   • 7.3. Call to action for stakeholders to prioritize and invest in green infrastructure solutions:
     • This white paper serves as a call to action for stakeholders in Charleston, including city officials, planners, developers, property owners, and community members, to prioritize and invest in green infrastructure solutions. By working together to incorporate green infrastructure practices into the city’s urban landscape, these stakeholders can help to ensure a more resilient, sustainable, and vibrant future for Charleston. This effort will require a comprehensive and integrated approach, including policy and regulatory support, financing and incentives, community engagement, and ongoing collaboration among all parties involved. By embracing green infrastructure as a key component of Charleston’s resilience strategy, the city can rise to the challenges posed by climate change and secure a brighter future for its residents and businesses

By implementing green infrastructure solutions such as rain gardens, bioswales, and permeable pavements, Charleston can enhance its stormwater management capabilities and increase its resilience to flooding events. This white paper provides a comprehensive overview of these innovative techniques, along with recommendations for integrating them into Charleston’s urban planning and policy framework. By investing in green infrastructure, Charleston can become a model for other coastal cities facing similar climate challenges, demonstrating the power of sustainable, nature-based solutions in the face of a changing climate.