understanding stormwater: managment in urban spaces

Have you ever wondered what happens to rainwater once it hits the ground in a city? Or how we can ensure it doesn't cause problems like flooding or pollution? Let's delve into the world of stormwater and its crucial role in urban planning and sustainability.

what is stormwater?

Stormwater is simply rainwater or melted snow. In natural environments, it plays a vital role in the water cycle, replenishing groundwater and nourishing vegetation. However, in urban areas, managing stormwater becomes essential due to the extensive use of impervious surfaces like roads and buildings. These surfaces prevent rainwater from naturally soaking into the ground, causing it to accumulate rapidly and potentially overwhelm urban drainage systems.

why manage stormwater?

The primary goal of stormwater management is to control the quantity and quality of runoff to mitigate severe environmental and infrastructure risks, some of the key drivers are:

• Flooding: urbanization disrupts the natural absorption and flow of rainwater, leading to increased runoff that can flood streets, homes, and businesses.

• Water Pollution: as stormwater flows over impervious surfaces, it picks up pollutants like oil, chemicals, and debris, which can contaminate rivers, lakes, and oceans if not properly managed.

• Erosion: rapid runoff erodes soil and stream banks, destabilizing ecosystems and damaging infrastructure.

key concepts in stormwater management

Effective management strategies focus on redirecting stormwater towards natural water bodies while simulating natural processes to minimize impacts. Key metrics that guide engineers and planners in designing solutions are:

• Runoff Flow Rate: the speed at which stormwater travels through drainage systems and natural channels.

• Runoff Volume: the total amount of stormwater discharged from a specific area during a rain event.

• Runoff Water Quality: the level of pollutants carried by stormwater, which can vary depending on the source and treatment processes.

These indicator characteristics help assess the performance of the stormwater management system. Optimizing for these factors allows systems to be thoughtfully designed, calibrated to natural systems, measured, and ultimately improved.

strategies for effective management

Several techniques are employed to manage stormwater effectively. Generally they are broken down into three main categories. These are three main places where different stormwater management strategies can be applied.

source control

This approach focused on incorporating elements that aim to reduce the overall runoff at the source (houses, streets, parks, buildings, etc.). Effective flow routing and green infrastructure techniques (such as rain gardens, bioswales, or permeable pavements) can be effective in reducing the overall runoff the conveyance and end of pipe systems manage.

conveyance control

This aspect prioritizes infrastructure elements to safely move stormwater runoff from sources to discharges and outfalls. These systems are often organized in a dual drainage system, where low flow events are carried through the minor system (an underground pipe network) and high flow events utilize the major system (an overland flow network).

end of pipe control

This part of the drainage system consists of constructed ponds or reservoirs that temporarily store stormwater, allowing pollutants to settle before gradual release. These are like surge tanks for the City's plumbing that capture extra runoff that doesn't quite fit into downstream systems. Typically end of pipe controls are classified into wet ponds, dry ponds, and constructed wetlands. Hybrid systems are emerging that aim to integrate aspects of all three.

the future of urban stormwater management

As cities grow and climate patterns shift, the importance of sustainable stormwater management practices continues to rise. Consequences of poor stormwater management can result in significant impacts to the public including mass flooding, deterioration of water quality, and property damage.

By building dynamic, integrated, and resilient cities engineers and planners can mitigate the adverse effects of urbanization on water resources.

Effective stormwater management ensures that our built environment coexists harmoniously with nature's water cycle. By implementing thoughtful strategies and embracing advancements in engineering and urban planning, we can create resilient and sustainable cities where the impact of development on water resources is minimized.