Stormwater, Runoff, and Nutrient Pollution
South Florida is a beautiful place that needs a lot of rainfall in order to thrive. With a population of over 6 million residents in Miami-Dade, Broward, and Palm Beach Counties, you can expect dense impervious (paved or non absorbent) surfaces in areas with dense population due to the number of buildings and roadways.
Think of it this way: Imagine you are at the top of a hill, you and some friends decide it would be fun to roll down. By coincidence, you are all wearing white or light colored clothing. Once you reach the bottom, you are all in similar positions but are covered in a variety of different things. One friend has brown smudges all over him, while most of you have grass seeds stuck on you, and another friend unknowingly rolled into a patch of mud. One thing is certain: you are all altered from your original state, some more than others.
Now imagine the same scenario of water running through a cityscape. Rainwater becomes runoff as it flows on impermeable surfaces, such as rooftops and roadways. Runoff starts picking up pollutants along the way. As water continues to move, its final landing spot intentionally merges into canal systems, rivers, draining into our groundwater sources, and even the ocean. This is a major source of pollution that can have adverse effects on our natural environment, aquatic life, drinking water and overall economy.
We are seeing more flooding than ever in our region due to sea level rise influencing groundwater levels and an increase in the occurrences of major storms. More flooding and rain means that our waters can become contaminated more easily. Basically anything that goes down your storm drain, are just a handful of the pollutants we find carried away with stormwater- car oil, gasoline, pesticides, chemical fertilizers, bacteria, pet waste, and microplastics. Managing what happens to our stormwater, and taking efforts towards reducing runoff, can promote water quality, reduce erosion and flooding, and mitigate the effects of pollution.
In Harmony with Green Infrastructure – (Bio)swales and Rain Gardens
One way the effects of stormwater can be reduced is by protecting and raising awareness of the benefits of swales and rain gardens. Swales are an aesthetically pleasing asset that have the ability to spruce up any property. At this point you are probably wondering, “so what is a swale or bioswale?” To put it simply, a swale is a shallow, sunken channel with gently sloping sides used to redirect water onto a pervious surface to reduce flooding and runoff pollution. Swale’s soils, plants, and microbes help break down the pollutants and absorb chemical fertilizer nutrients runoff picks up, while providing temporary water storage, supporting its green infrastructure title. The technical name for this sort of structure is a bioretention area.
A bioswale is essentially the same thing, but an upgraded version! Many can be seen on the outskirts of parking lots, street medians, and between parcels and highways in order to capture and treat the dirty runoff. Native plants are highly beneficial in these bioretention structures because of their hardiness, especially in South Florida, where marsh plants are extremely common.
There are different types of bioswales that are categorized by the type of soils and vegetation used, including grassed swales and vegetated bioswales. Grassed swales give a much more manicured look, but their effectiveness is often compromised when cars can easily park on them if there are no clear buffer zones or protection, such as wheel stops. The weight of a car will compact the soil and reduce a swale’s infiltration capacity. To combat this, trees and thick vegetation work harmoniously with bioswales to create more ground cover that protects the soils, and improves their ability to absorb and filter toxins from water.
It is crucial to raise awareness about protecting our environment and understanding the natural ability swales, native plants, trees, and more have towards mitigating flooding and strengthening the overall resilience of an area. In support, these green infrastructure also play a critical role in minimizing nutrient pollution, which subsequently improves water quality and protects sensitive ecosystems.