We learned so much from authors like Joe Mish and Joe Sapia who share observations of the natural world in our on-going “Voices of the Watershed” series. We are grateful for regular information-sharing from Streamkeepers and civic science volunteers, including writers Margo Persin and Howard Swerdloff. Folks like Rutgers doctoral candidate Kate Douthat teach us about plants and hydrology and stormwater flows through focused blog series. And student interns TaeHo Lee and April Callahan did a great job developing interviews with LRWP Board Members and others active in the watershed.
The following are the most read / viewed web pages on the LRWP website in 2019:
Join the LRWP and Middlesex County Water Resources Association on July 15 for a picnic and tour of green infrastructure and detention basins in Middlesex County with Rutgers County Extension Agent Michele Bakacs and Rutgers Doctoral Student and plant expert Kate Douthat.
We will then travel by van and car to tour detention basin retrofits for improved stormwater capture, return to Thompson Park for a group picnic, and those who wish to can continue on to visit the rain garden at the Spotswood Middle School.
By Kate Douthat, third year PhD candidate in the graduate program of Ecology and Evolution at Rutgers. Kate’s research is examining the plant communities that have formed in urban stormwater systems. She is interested in the extensive stormwater infrastructure network in New Jersey and how we can use plants to improve water quality. Kate loves to share her enthusiasm about plants and to teach the public about the stormwater systems in our backyards. She has agreed to develop a series of informative blogs for the LRWP’s readers and will also lead our #booksfortheriver book club starting Fall 2019. You can see more of her writing about plants and water resources at katedouthatecology.com
During the summer of 2018, I surveyed plants in stormwater detention basins throughout an urban and suburban area of central New Jersey. This study is aimed at improving water quality and wetland habitat by choosing the right plants for the job. Selecting appropriate sites for renovations and the choosing the best species to plant depends on many factors. Two important factors are the plants’ ability to survive in basin conditions and the natural tendency for certain plants to colonize basins regardless of what we plant there. One question I am addressing is how survival and colonization change depending on the surrounding landscape. Because catch basins at various locations receive different amounts of pollution and seeds, I expect to see different plants in different settings.
How does the surrounding landscape influence the plant community in a stormwater detention basin?
The adjacent land use and land cover influence wetland properties, including plant communities. Land cover is the type of stuff on the site, such as forest or roads. Land use is the activity that humans do on the site. Both factors affect plant communities. The surrounding landscape influences the plant community by the quantity and type of seeds available and by dispersal routes. One of the basic ways that plant communities are quantified is by the number of different species on a site, termed “species richness.” Paved roads around a wetland affect plant species richness and roads are particularly important dispersal routes for invasive plants. The proportion of native plants increases with forest cover in the surrounding area.
In this analysis, I am using the land use and land cover within 500 meters of each catch basin to explore relationships between adjacent land and the proportion of native species in the basin. I used a computer program to do exploratory regression. That technique takes each possible explanatory factor and tests the strength of the relationship between that factor and the factor of interest. In this case, the factors are land cover types and the percent native species at a site. I found that more adjacent commercial and service area leads to a lower percentage of native species in a catch basin. Transportation and utility areas, such as power line right-of-ways, also contributes to a lower percentage of native species. On the other hand, the percent of native species increases when a basin is surrounded by recreation area and wooded wetlands.
The following series of maps shows the areas around each catch basin. The maps are arranged from lowest percent native species to highest. In some cases there were two basins next two each other, so there are two numbers shown for the percent native species in each one individually. The land cover types with the strongest relationship to percent native species are colored. The reds and pinks are commercial or transitional areas, the light blues are wetlands, and the green is recreation area. (The names in the legends are the specific technical terms.)
The maps show that the amount of commercial or recreation area that surrounds a catch basin makes a big difference to the plants that live there. This result can help land managers decide which restoration goals are appropriate in different settings. For example, by the roadside, where there are more non-native species, a basin may be redesigned to filter pollution. Non-native species can perform this service as well as native species. However, in a park or recreation setting, where there are relatively more native species, a catch basin may be restored to include rare and sensitive native species. This analysis still needs fine tuning, but shows promise as a way to predict plant community characteristics based on the surrounding landscape.
This is the second of three articles in a series about stormwater management by Kate Douthat, a third year PhD candidate in the graduate program of Ecology and Evolution at Rutgers. Kate’s research is examining the plant communities that have formed in urban stormwater systems. She is interested in the extensive stormwater infrastructure network in New Jersey and how we can use plants to improve water quality. Kate loves to share her enthusiasm about plants and to teach the public about the stormwater systems in our backyards. She has agreed to develop a series of informative blogs for the LRWP’s readers and will also lead our #booksfortheriver book club starting Fall 2019. You can see more of her writing about plants and water resources on katedouthatecology.com
There are over 16,000 stormwater basins in all of New Jersey (https://hydro.rutgers.edu/). Locally, there are over 1500 detention basins in the Lower Raritan Watershed. Enhancing the functions of these basins represents a large-scale opportunity to restore environmental quality. Of the 16,000 basins in the state, approximately half are detention basins, meaning that they are designed to drain of stormwater within 72 hours, and remain dry most of the time. Most of these detention basins are lined with grass that is mown weekly or bi-weekly like a lawn. Some basins are lined with dense native plants that are mown only once per year instead of mown grass. Using native plants can save time and money and add badly-needed habitat for pollinators and other insects. When detention basins are lined with native plants, the thicker vegetation can also trap contaminants and prevent them from running into streams and drinking water sources. This type of approach to water management that mimics the natural water cycle is known as “green infrastructure”.
Replacing mown grass in detention basins with a mix of native vegetation in stormwater catch basins is a practice that is gaining momentum in New Jersey to prevent non-point source pollution from reaching streams and rivers. Non-point source pollution is the pollution picked up by rainwater from the ground that cannot be traced to any particular source. Contaminants of concern for drinking water and stream health include excess nutrients, which can choke waterways, and eroded sediments that are swept up in runoff. According to the USEPA, these non-point source pollutants are the leading cause of water quality problems today (https://www.epa.gov/nps/basic-information-about-nonpoint-source-nps-pollution).
While the concept of using
native plants in stormwater basins clearly has merit, we don’t yet which which
plants are best suited to this application. There are plant lists out there,
and we know which species live in natural wetlands; however, the plants in detention
basins must survive difficult conditions including flood, drought, and polluted
water. In many cases, the species that were originally planted in detention
basins have died out to be replaced by species that come in as seeds from the
surrounding area, so the planting lists need refinement. Research is required
to determine which plants can succeed in detention basins.
We also don’t know which the best filters are. In general, denser vegetation is better at filtering suspended solids, but it may be that different plants are successful at filtering different pollutants. New Jersey estimates for the removal of suspended solids in vegetated basins range from 60-90 percent based on the design. Estimates of removal rates for nutrients vary, and this process is less well understood. When designing and building basins, it is important to use plants that both survive and provide the best filtering possible. That is why two of the basic questions of my research are: 1) What are the dominant plant species in detention basins? and 2) Which species lead to the best water quality improvement?
By understanding the plants communities that are living in in stormwater basins and how they are related to factors in the environment, my goal is to improve their design and thus improve water quality and the beauty of the landscape. Replacing mown grass with mixed native vegetation can have a cascade of positive effects, including providing islands of refuge for songbirds, pollinators, and wetland plant species in urban landscapes.
This is the first of three articles in a series about stormwater management by Kate Douthat, a third year PhD candidate in the graduate program of Ecology and Evolution at Rutgers. Kate’s research is examining the plant communities that have formed in urban stormwater systems. She is interested in the extensive stormwater infrastructure network in New Jersey and how we can use plants to improve water quality. Kate loves to share her enthusiasm about plants and to teach the public about the stormwater systems in our backyards. She has agreed to develop a series of informative blogs for the LRWP’s readers and will also lead our #booksfortheriver book club starting Fall 2019. You can see more of her writing about plants and water resources on katedouthatecology.com
When it rains, water runs
across roads, parking lots, and lawns, picking up pollutants and debris. In
order to prevent flooding in developed areas, where the soil is not absorbent
because it is covered by pavement or buildings, this runoff, termed “stormwater,”
is channeled into storm drains. In nature, wetlands play an important role in
the landscape as regulators of flood waters and sinks for excess nutrients and
pollutants that are swept up in storm water. Green infrastructure is an
approach to water management that mimics natural storage and filtering
functions of wetlands by using plants and soils rather than drains and pipes.
We don’t yet have a good understanding of which plants are best suited to green
infrastructure, so that is the topic of my research.
Once stormwater enters a drain, it can have different fates. One type of municipal sewer system is called a combined sewer system. A combined sewer system combines sewage from your house (toilet sewage) with stormwater runoff from storm drains. This creates a large volume of contaminated water that must be treated at water treatment plants. This type of system is more common in older cities in the U.S., and in 21 cities in New Jersey (https://www.nj.gov/dep/dwq/cso-basics.htm). In New Jersey, most combined sewer systems are in cities near NYC, and a few around Philadelphia. The NJ Department of Environmental Protection hosts a web map to show those locations.
The second type of sewer system is a separate system. A separate system keeps sewage containing human waste in one set of pipes, and stormwater runoff from storm drains in another set of pipes. The latter has the the witty nickname MS4 (municipal separate storm sewer system). The sewage goes to a waste water treatment plant, while the stormwater is released to streams or rivers. This relieves pressure on waste water treatment plants and prevents overflows of untreated sewage. However, stormwater is usually contaminated with all of the urban dross it picks up, including pet waste, leaked gas and oil from our cars, excess lawn fertilizers and pesticides. Stormwater moves more quickly over smooth, paved surfaces than rough natural ones, so stormwater can accumulate quickly and cause floods.
In New Jersey and many places in the U.S., water from storm drains is temporarily stored in artificial detention basins or ponds before draining to streams and rivers. In principle this prevents the water from a rain storm from concentrating in a stream all at once and flooding its banks. A detention basin receives water from the storm sewer, then passively allows it to drain out the other side. The outlet pipe is small though, restricting the water leaving the basin to a low, steady volume. Detention basins were originally designed for flood control, but we are now realizing that they could be redesigned to provide more functions. The expanded functions for detention basins include pollutant filtering, ground water recharge, and provision of habitat.
Most detention basins are lined with grass that is mown weekly or biweekly like a lawn. In order to increase the functions of the basin, managers are changing to a mix of dense vegetation that is mown annually. This simple change can have a big impact and is the subject of my research. In my next post I’ll talk more about why I’m interested in studying detention basins, what I hope to find out, and how it can change our watershed for the better.