Impervious surfaces refer to materials such as concrete and asphalt that comprise roadways, parking areas, sidewalks, buildings, etc. Impervious surfaces prevent rainwater from naturally seeping into the ground, and a result, storm water instead runs across the environment as runoff. This can cause problems for not only humans, but the myriad of other species that utilize this landscape, in the form of flooding, water pollution, and even increased water temperatures across waterbodies. Flooding causes damage to manmade structures and can displace aquatic life, water pollution makes water unsafe to consume for all species, and increased water temperature can be fatal to aquatic life.
Understanding the impervious surface cover of Madison can help us see which areas are most likely to be impacted by storm water runoff. This map presents the impervious surface cover of Madison, NJ provided by the NJDEP’s Land Use 2012 data set. The land use/land cover layer displays polygons which were mapped from 2012 aerial photography, where an impervious surface estimate was made for each. This estimate was recorded in 5% increments of the total polygon area, ranging from 0-100%, depicted in the legend. The brighter the color, the higher percentage of impervious surfaces are present in that area.
Madison is mainly comprised of areas with 5-10% impervious surface cover, with the overall impervious surface cover mean of Madison estimated around 39%. Certain areas have impervious surface cover as high as 100%. The downtown of Madison is responsible for the most impervious areas, whereas the suburban and forest areas have less impervious areas.
Furthermore, the map can be toggled to display general land use throughout Madison. This data was provided from a more recent version of the NJDEP’s land use/land cover data set, published in 2015. Enabling this layer can help contextualize Madison’s high impervious surface cover, as most of Madison is comprised of urban areas. Additionally, a layer displaying roads throughout Madison is available to toggle. This data set was created by the New Jersey Office of Information Technology, Office of GIS (NJOGIS). Enabling this layer further displays how roads, and the areas around them, oftentimes have high percentages of impervious surface cover. A short video demonstrating how to toggle these layers can be accessed below.
The stormwater runoff management division of NJDEP recently implemented several methods of managing runoff, such as dry wells and pervious paving systems. A dry well is a subsurface stormwater facility that collects and stores runoff from clean rooftops, which is then discharged through infiltration into the subsoil. A pervious paving system is a stormwater management facility which asseses the impacts of land development. The system consists of a permeable surface course that allows stormwater to flow through it. In March 2021, new stormwater management rules were set in New Jersey which require major development projects to meet the groundwater recharge and stormwater runoff quality/quantity standards through the use of green infrastructure. The regulating technique of green infrastructure will ensure that the best management practices, like dry wells and pervious paving systems, are utilized to their maximum potential safely and efficiently.
This dataset helps regulators such as NJDEP and their clean water division monitor which areas in Madison produce the most stormwater runoff and therefore deserve immediate attention. Working to make this data more accessible and further studying changes in impervious surface cover are essential to the safety of Madison and its populace. This data could also be used to help inform regulations within the town, mainly the Stormwater Ordinance. It is also important to note the issue of flood equity within NJ. Floods disproportionately impact POC and other marginalized groups.
About the Data Sources:
The 2012 Land Use/Land Cover data set is the fifth in a series of land use mapping efforts began in 1986. Revisions and additions to the initial baseline layer were done in subsequent years from imagery captured in 1995-2012. The current presentation was created by comparing the 2007 LU/LC layer from NJDEP’s Geographic Information Systems database to 2012 color infrared imagery and delineating and coding the areas of change. Work for this data set was done by Aerial Information Systems, Inc., Redlands, CA, under direction of the New Jersey Department of Environmental Protection., Bureau of Geographic Information System. The 2015 Land Use/Land Cover data set builds upon this foundation, and is the sixth series of this mapping effort.
The Road Centerlines of New Jersey dataset was created out of a partnership between local GIS groups and the NJ Department of Transportation. This data set was published in 2021, and continues to be updated going into 2023.
A one-page summary of this information can be accessed here.
