As the awareness and importance of stormwater management grows, cities are looking to advancements in technology to reduce runoff pollution. Thus they are creating regulatory frameworks for residential and commercial developers to do their part by installing management and treatment systems on their properties. The goals for these regulations are two-fold. First it is to retain as much water on a site as possible, which promotes the recharge of aquifers. Second is to reduce the storm impact on city infrastructure by slowing down run-off from properties. But what are the main differences between detention and infiltration vs. harvesting and retention? Continue reading to learn some of the most common ways you can manage stormwater on your property.
Detention and Infiltration vs. Harvesting and Retention
You may be familiar with stormwater detention, but not up to speed on the primary differences between detention and harvesting. To make a knowledgeable choice about managing your site’s stormwater, it’s crucial to grasp these processes, considering both cost and efficacy.
Stormwater detention is the storage of stormwater runoff within large or even small storage systems or retention ponds. After a set period of time, detention systems then release water into a natural watercourse. This process can help reduce flooding during heavy rainfall events by allowing water levels in creeks, rivers, and municipal drainage systems to drop before they overflow their banks, causing erosion, or backup and flood urban areas. Stormwater harvesting refers to the collection, filtration, and storage of rainwater for reuse; either onsite (i.e., landscape irrigation) or offsite. A variety of technologies are used for harvesting rainwater including cisterns made from concrete tanks or precast storage vaults.
Stormwater Detention
Detention revolves around collecting water and storing it for a slow, metered release over time. This can be done by designing and building engineered underground storage vaults, basins or ponds. These areas will hold water during heavy rains for volume control while preventing overflow into streets or other areas where it could cause damage or disruption. Over the ensuing days, the water is gradually released at a rate the local infrastructure can accommodate.
Stormwater Retention / Infiltration
Retention and Infiltration involves keeping that water on a given site as it would have been in a natural pervious soil. This allows stormwater to seep into soil mimicking a more natural process of recharging the earth’s groundwater, rivers, lakes and aquifers rather than collecting it or simply redirecting the runoff.
Stormwater infiltration is the process of water entering the soil. It occurs naturally, but it can also be enhanced by man-made structures like concrete vaults, retention basins, or drywells. Infiltration helps manage stormwater, as it reduces runoff volumes and regulates the rate at which runoff enters streams, rivers, lakes and groundwater supplies.
Infiltration isn’t always a straightforward option for managing stormwater in all areas. Urban areas tend to have large impermeable surfaces that prevent water from infiltrating (i.e. concrete sidewalks or parking lots). Through precise engineering of infiltration galleries or drywells, more water can be retained on site. This serves two purposes. 1) It helps meet the regulatory tenants of Low Impact Development (LID) by keeping the site as close as possible to naturally occurring water retention. 2) It reduces the impact and cost of treatment and discharge through city infrastructure. Overall, onsite retention and infiltration is the first and best solution for developers, the environment, and city infrastructure.
Stormwater Harvesting
Stormwater harvesting is an innovative and eco-friendly surface water management strategy. This approach involves capturing, collecting, and storing rainwater directly on site for a variety of practical reuses, such as irrigation, landscape hydration, supplying wastewater flush tanks, and even groundwater replenishment. This involves much of the same infrastructure as other stormwater storage systems, and it is another way to capture water for future uses while preventing problems associated with increased runoff volume during heavy rain events.
Conclusion
When it comes to stormwater management, there are many options available. The most effective method is usually a combination of several different types. These include detention and retention systems, as well as infiltration galleries and bioretention. In the end, it all comes down to what works best for your particular site conditions, budget, and goals.
