2018 Eco-Resolutions Part 1: Rain Gardens for Storm Water ManagementPosted on January 1, 2018
We all know the end of the year is a time for reflection and resolution making. However cliché, this is healthy and productive tradition that allows us to take stock of the past year, learn from our actions, and put forth new intentions. In that spirit, for the next seven days, we’ll provide you with Seven Ecological Resolutions for 2018, grounded in a recap of environmental news and events of 2017.
2017 was definitely a rough year for the environment. With a climate change denier as Commander In Chief, and the Environmental Protection Agency’s biggest critic now at its helm, the stage was set for a year of assaults on the environment at a time when we need to protect it the most. In twelve short months, the Trump administration, upended 60 environmental regulations, approved the controversial Keystone XL and DAPL pipelines, and drastically reduced the size of national monuments created in the Obama administration while opening them up to private mining, extraction and ranching interests.
But fear not! Revolution starts in thy own backyard. There is so much we can do at the community and individual level to preserve and protect the environments we so cherish.
The Issue: Storm water runoff
It is no surprise that population growth and the associated development of once rural lands are impacting our environment. How and where we build matters. This year, Houston suffered the worst flooding in history, in part from record rainfalls from Hurricane Harvey, but also from urban sprawl, weak zoning regulations, and a disjointed storm water management strategy that failed to absorb some of storm surge.
Impervious surfaces are those that do not allow water to infiltrate into the soils (asphalt, concrete, roofs, etc); rather, they increase the flow rate of storm water by two to three times compared to vegetated areas.
In wake of the natural disaster, Texas A&M professor and flood plain management expert, Sam Brody lamented to CNN, "We need a broader strategy that protects areas with natural infrastructure like wetlands, which are still the best system we have to hold, store and slowly release floodwaters."
Brody is right. Wetlands are an essential ecosystem from a biodiversity standpoint and a storm water management and remediation perspective (see our latest SlideShare for more on the value of wet meadows). If your property includes or borders a wetland, protect it. If not, there are landscape design solutions that can combat runoff and build ecological value.
The Solution: Rain Gardens & Bio-Retention
Bio-retention is a land-use strategy that employs the properties of plants, microbes and soils to control the quality and quantity of water on a landscape (Dunnet & Clayden, Raingardens 2007). Carefully selected plants are natural sponges: their root growth prevents soil compaction through aeration, allowing for greater water infiltration; microbial communities in the soil help plants’ roots uptake water and nutrients.
For the homeowner, bio-retention often takes the form of a rain garden. A rain garden is designed to gather water during a high storm event and allow it to dissipate into the soil. Otherwise, run-off collects pollutants such as oil, gasoline, pesticides, fertilizers, animal feces, sediments, heavy metals and bacteria along the way. Much of our current storm water systems are designed to collect water quickly and funnel it away from development, often into rivers, streams and oceans, or costly water treatment plants. This is a classic example of man vs. nature. Instead of maximizing nature’s own system of checks and balances, we pave and pipe our own ineffective ones. In 2018, let’s do better.
If you experience flooding or ponding on your property, a rain garden might be right for you. Rain gardens are typically dug 6” deep and planted with a selection of native plants that can tolerate flooding and drought. Rain gardens are not water gardens! This is a common misconception. Your rain garden should drain in 6 – 24 hours, depending on the storm event; rain gardens are not ponds, and will not encourage mosquito breeding (mosquitos need much longer to lay and hatch eggs in water).
Abiove: Rain Garden during storm event
Below: Construction of a rain garden at WCC's Native Plant Center.
Uconn has a great resource for determining the impervious surface area of your property and calculating the rain garden area needed to absorb run-off. Your rain garden should be located in the path of run-off, such as near a gutter or downspout. However, if you have a basement, do not design your rain garden within ten feet of the building.
Test the infiltration rate of the soil in your desired location before going any further. Sandy soils drain the fastest, and clay soils are nearly impermeable. An infiltration rate of 1-2 inches per hour is ideal for a rain garden. Soil amendments such as gypsum and soil surfactant can aid in absorption. Often gravel or river rock are employed to prevent erosion near the run-off inflow and bordering over-flow areas.
Plant selection should consist of species that flourish in mesic soils – those that are neither excessively wet or dry. Generally herbaceous plants and grasses work best, but you can experiment with trees, shrubs and annuals too, as suits your design aesthetic. Natives are always preferable when possible – but more on that later in this series.
If you need assistance designing your rain garden, or a broader assessment of drainage on your property, call us to speak with our team of landscape ecologists about a consultation.