Water drainage is a typical problem for many homeowners, particularly as storms get heavier and more intense. In this article, partially adapted from a tremendous set of resources by the UGA extension Office, we'll be walking you through the most common drainage issues, how to fix them naturally, and the native plants that will help you along the way.
Impervious surfaces disturb natural hydrology
The main culprit for flooding issues in urban and suburban areas is cement. In a natural setting, rain falls to the ground and either percolates through the soil into the groundwater, or runs off into streams, ponds, wetlands, rivers, lakes, and ultimately oceans. However, in developed areas, cement, grass, and compacted soil disrupt this natural cycle, making it harder for the water to flow naturally, impacting both water quantity and quality. In a natural environment, approximately 50% of rainfall is sunk into the ground, with only 10% running off into rivers and streams. But in developed areas those numbers are reversed, with 55% of rainfall running off the surface and the amount of rainfall that infiltrates into the soil to recharge groundwater decreases from 50% to 15%.
Negative effects of storm runoff
There are a host of negative effects of urban and suburban drainage solutions.
More Flooding; Bigger Floods
In developed areas, the prevalence of cement and compacted soil significantly increases runoff. Impermeable surfaces like roads, sidewalks, and buildings prevent water from infiltrating the ground. Similarly, compacted soil (an unfortunate side effect of all the grass) reduces the soil's ability to absorb water. As a result, rainfall quickly turns into surface runoff, leading to higher volumes of water flowing into storm drains, streams, and rivers. This can cause frequent and severe flooding, as the natural process of water percolation is disrupted.
Groundwater isn't replenished
The flip side of increased stormwater runoff is that cement and compacted soil also hinder the replenishment of groundwater by preventing water from seeping into the earth. Consequently, less water infiltrates into the ground, leading to a significant decrease in groundwater recharge. This disruption of the natural water cycle can result in lowered water tables and diminished groundwater supplies.
Increased water pollution
During dry periods, impervious surfaces also accumulate pollutants so that when it rains, these pollutants are quickly and easily picked up by the runoff. As the runoff collects, so do the pollutants. Impervious surfaces are usually interconnected to swiftly channel stormwater to natural streams and water bodies, which means that pollutants are rapidly transported into these water bodies. Essentially, impervious surfaces act as express routes for various pollutants. In a natural landscape, soil and plants work together to purify the infiltrated water, so impervious surfaces both keep collect and convey pollutants to streams while also keeping natural filtering processes from working.
Polluted Rainwater: the no. 1 water quality issue
The EPA has recently declared stormwater pollution to be the no. 1 water quality problem in the United States, and that's because so much of the pollution that enters our waterways doesn't have an identifiable source, making pollutant removal much harder.
Here are a few of the most common pollutants:
Concentrated nutrients: Nitrogen and phosphorus are the most common nutrients found in storm runoff, stemming from fertilizer use, animal waste and leaks from septic systems or sewer lines. These nutrients, while beneficial in many instances, create ecological problems when they concentrate in waterways.
Toxic contaminants: In addition to nutrients, impervious surfaces also concentrate toxic contaminants like hydrocarbons, such as fuels and lubricants from cars, and metals that wash off streets and parking lots.
Sediment and organic material: Sediment from eroded ground can disrupt the natural flow of water and alter the chemistry of the water, while organic material, such as yard waste, can decrease the oxygen content by feeding microbial activity.
Heat: Increase water temperature can also decrease oxygen in the water.
traditional drainage design
The purpose of traditional drainage solutions is to reduce flooding by collecting rainwater and moving it as quickly as possible into streams and retention ponds. Not only does this method not necessarily solve flooding issues, but it also contributes to water pollution and generally increases the potential for flooding downstream.
Natural drainage solutions
In the last 20 years, engineers have started to realize the error of their ways and have begun finding more natural ways to improve water quality and reduce stormwater volumes. Natural drainage solutions tend to incorporate the following design principles:
Break up impervious surfaces
A simple fix is to create buffers between impervious surfaces so that water has a chance to infiltrate the ground, rather than collecting into cascades of surface water.
Diffuse stormwater
Another principle is to spread water out rather than collect in centralized areas like storm drains and retention ponds.
Manage close to the source
The easiest solution for homeowners is to manage stormwater onsite, rather than sending it off into drains. Rain gardens and other natural water solutions take water runoff from driveways and roofs and distribute them over greenspace, which makes it easier for the water to go into the ground.
Yard Drainage Solutions
There are a host of ways homeowners can naturally manage stormwater onsite, increasing water infiltration, water quality, and decreasing flooding downstream. Here are just a few of them:
Rain Gardens:Â Creating depressions planted with native vegetation that capture and absorb runoff.
Permeable Pavements:Â Installing driveways and walkways made from materials that allow water to seep through.
Rain Barrels and Cisterns:Â Collecting rainwater from rooftops for later use in irrigation, reducing runoff.
Vegetated Swales:Â Designing shallow, vegetated channels to direct and filter stormwater.
Green Roofs:Â Installing rooftop gardens to absorb rainfall and reduce runoff.
Mulching:Â Applying mulch in garden beds to enhance soil infiltration and retain moisture.
Soil Aeration:Â Periodically aerating lawns to improve soil porosity and water absorption.
Tree Planting:Â Planting trees to increase canopy cover, reducing runoff and promoting groundwater recharge.
Rain Garden inspiration
Need inspiration for building your rain garden. Check out our Rain Garden Inspo Board on Pinterest!
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