1. Rain Gardens and Bioswales

Rain Gardens: Shallow, vegetated areas designed to absorb and filter stormwater runoff. They can be installed in public spaces or residential areas to reduce water flow and prevent flooding.

Bioswales: Landscape features designed to channel and absorb rainwater, typically placed along roads, parking lots, and walkways. They slow water flow, filter pollutants, and allow water to soak into the ground.

2. Permeable Pavement

Pavement materials that allow water to pass through them into the ground rather than causing runoff. Permeable pavement can be used in parking lots, sidewalks, and streets, reducing flood risks in urban environments by promoting groundwater recharge.

3. Floodplain Restoration

Restoring natural floodplains by removing man-made barriers and allowing rivers to spread out during floods. This can help reduce the speed and intensity of water flow during floods, mitigating damage to urban areas.

4. Levees and Flood Walls

Levees: Earthen embankments built along rivers to contain floodwaters. They can protect urban areas from river overflows but must be designed to handle the maximum expected flood levels.

Flood Walls: Concrete barriers built in vulnerable areas to prevent floodwaters from reaching critical infrastructure or residential zones.

5. Detention and Retention Ponds

Detention Ponds: Temporary water storage areas that hold excess stormwater and gradually release it into the drainage system after the storm. These are often used in urban areas to manage runoff.

Retention Ponds: Designed to hold water permanently, these ponds collect stormwater and allow it to slowly infiltrate into the ground or be absorbed by plants, reducing runoff volume and flood risk.

6. Green Roofs

Rooftop gardens that absorb rainwater, provide insulation, and reduce the amount of stormwater that flows off buildings. Green roofs can significantly reduce urban runoff and alleviate pressure on drainage systems during storms.

7. Wetland Restoration and Creation

Restoring or creating wetlands that act as natural sponges, absorbing excess water during floods and releasing it slowly. Wetlands can significantly reduce the volume and speed of water flowing into urban areas.

8. Stormwater Retention Tanks

Underground or above-ground tanks that collect and store excess stormwater, which can later be reused for irrigation or released slowly into the drainage system. This solution is often used in areas with limited space for ponds or gardens.

9. Sustainable Urban Drainage Systems (SUDS)

A holistic approach that integrates various drainage solutions (e.g., green roofs, permeable pavement, bioswales, and rain gardens) to reduce runoff and increase water infiltration. SUDS are designed to mimic natural water cycles and reduce the impact of urbanization on flooding.

10. River Channelization and Diversion

Modifying or redirecting river channels to control the flow of water and reduce flood risk. In mountainous areas, this can involve rerouting rivers to less vulnerable areas or straightening channels to move water faster through flood-prone regions.

11. Reforestation and Afforestation

Planting trees in areas surrounding cities, especially in flood-prone valleys or on slopes, to help absorb rainwater, reduce runoff, and prevent erosion. Forested areas are essential for slowing the flow of water and preventing flash floods.

12. Terracing

Creating stepped terraces on slopes to slow down water runoff and reduce soil erosion. This technique is especially effective in mountainous areas like Asheville and can be combined with reforestation to manage water flow.

13. Early Warning Systems and Flood Barriers

Deploying mobile flood barriers that can be installed quickly when floods are imminent, such as temporary walls or inflatable flood barriers. These systems are often used in conjunction with advanced early warning systems that provide alerts based on weather patterns and water levels.

14. Elevating Buildings and Infrastructure

Raising buildings, roads, and other infrastructure above expected flood levels, particularly in vulnerable areas. In regions like Asheville, this could mean designing buildings on stilts or constructing elevated roads and walkways to prevent damage during floods.

15. Underground Stormwater Tunnels

Large tunnels constructed beneath cities to collect and divert excess stormwater away from urban areas. These tunnels are often used in conjunction with other stormwater management systems to reduce flooding risks.