Urbanization—the process of conversion from forests, grasslands, or agricultural fields to predominantly residential, commercial, and industrial settings—can cause profound changes to the pathways that rainfall takes to become streamflow. This landscape conversion leads to less water infiltrating into soil and more water running directly into streams and other nearby water bodies (such as lakes, wetlands, and bayous). Urban water runoff carries pollutants that have accumulated on the landscape and in soil since the previous rainfall. If the concentrations of pollutants in streams are large enough, they can cause problems for the organisms that live in streams as well as those in the bays and bayous those streams flow into (often called receiving waters).
Stormwater conveyance in Santa Rosa nd Escambia counties.
Photo: Matt Deitch
Local governments play a key role in mitigating the impacts of urbanization on aquatic ecosystems. In northwest Florida, County government is often responsible for limiting pollutant inputs from the network of surface and underground stormwater conveyances known as “municipal separate storm sewer systems” (abbreviated as MS4s). The United States EPA requires urban areas to be regulated as sources of pollutant discharge through their National Pollutant Discharge Elimination System (abbreviated NPDES); departments within Escambia County and Santa Rosa County government coordinate the administration of these permits with the US EPA.
The requirements of these MS4 water quality permits vary depending on the population of the area. Permits for medium and large cities or counties having populations greater than 100,000 are categorized as “Phase I” MS4s, while areas with smaller populations are categorized as being “Phase II” MS4s. These two categories have many similar requirements, but also have a few important differences. Permits for both types of MS4s require local agencies to develop methods for community outreach on stormwater pollution issues, controlling runoff from construction sites, and requiring stormwater management in new developments. In addition to the requirements listed above, Phase I MS4s require the implementation of a water quality monitoring program and a plan to reduce pollutants from developed areas.
Stormwater conveyance in Santa Rosa and Escambia counties.
Photo: Matt Deitch
In Spring 2020, the southern portion of Santa Rosa County transitioned from a Phase II MS4 region to Phase I. This means that Santa Rosa County will begin implementation of a surface water monitoring program to evaluate pollutant concentrations in stormwater conveyances (including creeks); and develop plans for reducing pollutants from their MS4s entering the Pensacola Bay System. This program will make important contributions to understanding the effects of urban development on our local streams and estuaries, and improve water quality in the Pensacola Bay System.
This is a great opportunity to remind us of the importance of disposing our personal protective equipment including face masks, plastic gloves, and other single-use items we use to protect ourselves from the coronavirus in the trash after use. Leaving it on the curb or in parking lots means that it can wash into stormwater ponds or creeks and bayous, which can cause problems for the animals that live there.
Stormwater conveyance in Escambia and Santa Rosa counties.
Photo: Matt Deitch
Flooding and poor water quality are common issues of concern in the Florida Panhandle. Our frequent heavy rains cause water to quickly run off rooftop, parking lot, and driveway surfaces; this runoff water carries with it the chemicals deposited on land surfaces between rain events by direct application (such as landscape fertilizers) as well as through wind and circulation, a process referred to as atmospheric deposition. Surface water that runs off our developed urban and residential landscape is usually routed into stormwater drains and sewers, and then into stormwater detention ponds or directly into surface streams.
Dry stormwater pond in Escambia County.
Photo: Matt Deitch
Conventional methods for dealing with stormwater runoff is through the use of stormwater ponds. Stormwater ponds allow water to slowly infiltrate into the soil before moving to streams or wetlands via shallow groundwater pathways. Typically hidden behind shopping centers or in the back of residential subdivisions, stormwater ponds attenuate flooding by delaying the time when water reaches the stream and are intended to improve water quality through microbial processes (such as denitrification) or plant uptake, particularly focusing on reducing the amount of nitrogen and phosphorus that reaches nearby streams. However, the efficacy of stormwater ponds is highly variable (many do not function as intended), and they often are visually unattractive aspects of a community.
A backyrad rain garden after installation near Navarre FL.
Photo: Nikki Bennett
Stormwater managers in other parts of Florida are increasingly utilizing a suite of management features termed “green infrastructure” as alternatives to stormwater ponds to reduce floodwaters and improve water quality before it enters nearby streams and wetlands. Green infrastructure, which includes features such as rain gardens, green rooftops, rainwater cisterns, bioswales, and permeable pavers, is designed to slow water down and reduce pollutant concentrations by mimicking natural processes of infiltration and biological uptake at its source—off the rooftops, driveways, roads, and parking lots where stormwater first concentrates. As a result, green infrastructure reduces surface runoff that occurs during storm events, leading to less flooding downstream. With the magnitude of peak flow reduced, stormwater runoff is also likely to carry lower amounts of pollutants downstream. In addition to their capacity to reduce flooding and improve water quality, green infrastructure can have many other benefits. It is often visually appealing, with vegetation typically selected to be visually attractive, appropriate for local conditions, and requiring low maintenance.
Rain garden at the VA Central Western Massachusetts Health Care System facility.
Photo: US Air Force
With our frequent rainfall, moderately developed urban areas, and expanding communities, the Florida Panhandle is ideal for using green infrastructure to reduce flooding and improve water quality. Features such as bioswales, rain gardens, and permeable pavement can be added to new development to mitigate stormwater runoff; they can also be added to existing neighborhoods to reduce flooding where roadside areas or other shared spaces allow. In addition to mitigating the effects of rainfall, green infrastructure can also improve property values because of their visual appeal. For green infrastructure techniques to be effective, they require widespread use throughout a neighborhood rather than at a handful of locations; so if it sounds like green infrastructure would benefit your community, talk with your neighbors and reach out to UF IFAS agents to discuss how it could be added to your community!