On the downside, there is more maintenance needed, such as lawn mowing and shrub trimming, and possibly more opportunities for mosquitoes to multiply! Also, with large amounts of rainfall in short periods of time, like the typical storms seen in the past weeks, the ground gets saturated, causing water to flow quickly across impervious surfaces. Moving quickly, not having a chance to percolate into the soil, the water picks up pollutants as it travels to the swales and storm drains. The pollutants in the storm water runoff come from the impervious surfaces such as roadways, driveways, sidewalks, roofs, and residues on vegetation, and mostly consist of organic particles, pesticides, fertilizers, gas, oils, and larger debris.
Just recently, two communities north of Marco Island had to close their beaches for many days due to high levels of bacteria that could be harmful to beach goers and swimmers. The Florida Department of Health stated the high bacteria concentrations came from storm water runoff. Fortunately, the Marco Island beaches have not had high levels of bacteria in the past few years. Our beach waters are healthy!
If the storm water is not treated or “cleaned” before it flows into the storm water outfalls and into the canals and lakes of Marco Island, the pollutants are loaded into the surface waters that surround us and that we depend on for aesthetics, recreation and even a good fish dinner. One hundred miles of canals on Marco Island equates to over one hundred miles of roadways. And, of course, adding in roof tops, driveways, sidewalks, bricked features in yards, docks and pool decks means this small island has a large area of impervious surfaces which in turn creates high flows of storm water runoff carrying pollutants to the lakes, canal waterways, Marco River and Gulf of Mexico. A typical urbanized block absorbs four times less rainwater than a natural wooded area. Storm water runoff treatment is extremely important to protect and maintain the quality of the surface waters.
Over the past few years, Marco Island has improved the over 1,500 storm water outfalls throughout the island by installing treatment systems referred to as “storm inlet skimmer boxes.” The skimmer boxes consist of two steps to treat or “clean” storm water runoff before the water flows into the canal system. Within the box, encircling the grate like a boom is a hydrocarbon filter. The boom-like filter catches larger debris that is carried by storm water runoff as well as absorbing fertilizer, pesticide, and organic particles. When the rain is light or it is a slow moving storm, the storm water is low to mediumin flow; the water has to travel through the boom-like filter before entering the drain. If there is a deluge with many inches of rain in a short period of time, storm water flow is high. The water will travel through, and cascade over, the boom prior to entering the drain. Once in the drain, the second step to treating or “cleaning” the runoff water is the graduated sieve which is a series of screening that progressively sieves, or filters, the water through smaller and smaller grates or filters, collecting nutrients and silt that still remains in the runoff water. Water may stand and particles settle in the graduated sieve system until the storm water flow is high enough to move the water through the progressive screening system then to the outfall to surface waters.
Now that septic systems, with their accompanying drain field areas, are being eliminated on the island, there is opportunity for individual property owners to reduce storm runoff flows and to reduce the impact of the pollutants found in storm water that enter local storm runoff systems. Many properties have large expanses of lawn, or turf grass, that covered the septic system drain field area. To reduce lawn care maintenance and costs, and to reduce the use of fewer chemicals to treat weeds and pests, consider creating a beautiful spot or oasis in your yard. Consider a rain garden.
A rain garden will slow down the rush of water from storm water runoff; holding the water for a short period of time which allows it to naturally percolate into the ground, not just to rush to an outfall. A rain garden is a place where water-tolerant plants provide a pretty, three-dimensional area that allows runoff from a roof’s downspout or driveway to re-enter the soil. It also provides wildlife with a great habitat. Easy to design, this type of garden is a shallow depression that is planted with deep-rooted, water tolerant plants and grasses. It can be large, small, and any shape. Typically, the rain gardens have been messy and designed to be meadow-like which is not exactly compatible with the Marco Island landscape. This garden, when Florida Friendly Landscape (FFL) concepts are followed, can incorporate many species of Florida wild flowers, native ferns, shrubs and trees. In south Florida, a few ideas for a low, water retaining area are: Wax Myrtle, Dahoon Holly, Gulf Muhlygrass, Golden Canna, or even a Loblolly Bay tree, but even stones or rocks designed as a dry creek bed can be attractive. (University of Florida Extension statistics show that trees are very efficient in rain gardens, as one tree can reduce storm water runoff by 4,000 gallons per year!)
So, now that it’s raining and pouring, consider a rain garden as a cost effective, low-tech water quality protection and conservation technique that can be easily incorporated into your south Florida island yard. For more information, contact collier.ifas.ufl.edu.