Where the Rain Meets the Road: How Urbanization and Climate Change are Affecting Our Waters
by Wenley Ferguson, David Prescott, Cindy Sabato
Within the Narragansett Bay watershed, the water in 162 miles of streams, 57 square miles of estuarine waters where freshwater and saltwater mix, and 4,800 acres of ponds and lakes is too polluted for aquatic life, according to the State of the Narragansett Bay and Its Watershed report. Location matters; the report tells us the water is more polluted in urbanized areas than rural areas and gets cleaner and safer the further south it flows.
Why? One big factor in water pollution is how we use our land, and that is very much tied to location. More and more development within the watershed has turned forest land and open space into streets, buildings and parking lots, spurring two important changes in the way rainfall affects our waters. When rain falls onto natural areas of land, it soaks into the soil, where excess nutrients, bacteria and other pollutants are filtered out naturally. When rain falls onto parking lots, streets and roofs, it can’t soak in, and instead runs right off, picking up and carrying pollutants into our rivers and the Bay in higher-than-normal volumes and velocity. This is commonly known as “polluted runoff.”
Water quality begins to become degraded when more than 10 percent of the land in a watershed is hardened by roadways, parking lots, driveways and roofs. According to the State of Narragansett Bay and Its Watershed report, 14 percent of the watershed is covered by hard surfaces, and more than one-third of its residents use septic systems and cesspools, “some of which are thought to be significant sources of nutrients and contaminants entering rivers and the Bay.” Unfortunately, more and more forested land around the watershed is being developed, particularly in the Taunton River and Pawtuxet River basins.
Climate change also brings with it some important changes to precipitation patterns, making the effects of urbanization on water pollution even worse. According to the report, Providence has been getting nearly half an inch more rain every decade since 1895. Climate models predict that number will go up to three inches per decade in the future. What’s more, most of the increased precipitation comes during intense downpours, which have more than doubled in frequency since 1950. More intense rainfall, combined with increased volume and velocity of runoff carrying pollution over hard surfaces into our waters, is all bad news for water quality. On top of that, rain and snow are coming more often in large events with drier spells in between. When all of this rainfall runs off the hard surfaces of our cities and neighborhoods directly into our rivers and the Bay, our groundwater is not replenished, and we suffer from more frequent droughts.
The broad, cumulative effects of increased development and precipitation changes include more pollution and more beach closures, adding to Save The Bay’s sense of urgency to address the problem of polluted runoff. We have been partnering with multiple municipalities and other organizations over the last decade to reduce the impacts of polluted runoff from the Bay’s watershed:
In Providence’s Roger Williams Park Pond, a tributary of the Pawtuxet River, we have collaborated with the City of Providence Parks Department on planning, installing and maintaining planted areas where polluted runoff from the park and neighborhood roads is diverted and absorbed into the ground. We continue to work with the City to restore buffers along the pond to improve water quality and discourage geese feeding.
Along the Seekonk River in Providence, runoff flows untreated down a steep bank, causing significant shoreline erosion. We are working with the City of Providence Planning Department on a project to address the erosion and to reduce the impacts of polluted runoff by installing infiltration areas further inland.
In Bristol, we continue to work with the Town to manage stormwater that discharges into Bristol Harbor from the Silver Creek watershed. Students from Mount Hope High have installed rain gardens on the campus adjacent to Silver Creek.
At Barrington Beach, we are working with the Town and the University of New Hampshire’s Stormwater Center to address stormwater that flows from neighborhood streets down to Barrington Beach, causing beach erosion and water quality problems. We have installed infiltration areas and replaced a section of the beach parking lot with a protective dune of beach grass. We are now looking further inland to identify areas where we can reduce the volume and velocity of the runoff that flows down to the beach from neighborhood streets.
In North Kingstown, at the end of the Calf Pasture Point bike path, asphalt was removed and an infiltration area installed. We are working with the Town of North Kingstown to address the high erosion rate in this area that is threatening the lower sections of the infiltration area.
In Newport, in partnership with the city, University of Rhode Island Sea Grant and University of New Hampshire Stormwater Center, we worked on conceptual designs for a stormwater infiltration area along an access path to the Cliff Walk, where erosion from stormwater was affecting accessibility and discharging to a local beach. And Rogers High School biology students worked with Save The Bay to plant rain gardens to filter runoff from the school parking lot.
In Warren, we are helping the town restore a stream corridor to enhance its flood storage capacity and to manage and treat polluted runoff along the Warren River and Belcher Cove. We are also identifying low-lying coastal roads subject to saltwater flooding to carve back and install stormwater management practices.
Hill, Ninigret and Quonochontaug ponds. Fifteen substandard septic systems are being replaced with newer systems that utilize nitrogen-reducing technology. Save The Bay is installing six rain gardens to promote stormwater infiltration and serve as public demonstration projects. And our Bay-Friendly Living guide is being distributed to homeowners.