Green Infrastructure Coalition, A project of the Environment Council of RI
Green Infrastructure Coalition

Stormwater 101

Storm water is generated when rain hits a hard surface — even hard earth — and begins to trickle across the surface. Along the way it picks up fertilizer from lawns and landscaping, animal droppings, automotive fluids from vehicles, de-icing sand and chemicals, and litter and dumps its polluted load into a drain or directly into a river or pond. Storm water can be snow melting and carrying grains of soil, leaves, litter, and oil into a drain or ditch/swale. The result is water that is unsafe for human use or for the aquatic ecosystem.

Stormwater can exacerbate a flood by pouring more water into a swollen river or stream. Because of its load of sand and trash, stormwater can clog grates and pipes, spreading the flood. As climate change brings more intense storms and higher sea levels, green infrastructure techniques can mitigate cause and effect. Stormwater Management Information from the CRMC.

Green Infrastructure refers to landscape construction using natural and artificial components to “soften” the urban hard structures; to provide climate-change resiliance, shade, oxygen, air-quality improvement; and to infiltrate stormwater into the ground. These measures mitigate the impact of human development on water quality and temperature.

Image Credit: Kate Venturini

Green Infrastructure may include:


When foliated, in addition to taking up some carbon dioxide, trees evapotranspire, sucking up and releasing moisture into the air, which for a mature maple may be 100 gallons per day. Planted strategically, a tree’s shade can reduce the radiant energy soaking into a building or paved area.

Trees filter boxes

A below-ground slotted box or cylinder to help infiltrate runoff into the root system and the ground; it may also have an outlet into a storm drainage system. The filter box keeps the roots from growing under sidewalks and driveways as it acts as a physical barrier.

Rain gardens

Shallow beds designed to infiltrate stormwater into the earth. Typically planted with perennials and shrubs that can withstand periods of dry and inundation, they drain within a few hours.

Vegetated swales

Linear shallow borders to roadways that are often planted with grasses whose matted roots form a trough to convey storm water.

Pocket wetlands

Small, engineered, constantly wet areas that support plants habituated to wetlands. Used to mitigate peak flows.

Urban agriculture

Row crop and small animal operations in densely populated areas that can take advantage of storm run-off for a source of water.

Vegetated median strips

Between cut-curbing that separate road lanes or sidewalk from road, the space can infiltrate water and provide an esthetic element in urban landscape.

Green roofs

Roofs that are engineered for weight and moisture protection to support natural low-growing plants that survive heat and sporadic rain. Gardens can also be planted on roofs that are designed for shallow-rooted plants or that are raised beds. These act as insulators as well as absorbing rain that falls on roof.

Infiltration planters

Below grade trenches, filled with gravel and soil, and planted with small trees and shrubs that can withstand periods of dry and inundation.

Infiltration trenches

Often used parallel to parking lots and roads, the sand and gravel of these 3 – 12-foot deep trenches collect sediment and incidental automotive pollution as they allow water to sink into the earth beneath.

Permeable pavement

For construction of roads and driveways, a sustainable material that ranges from gridded metal, open cement blocks, cobbles, to pervious asphalt and cement that bears the weight of vehicles while permitting rain to permeate the earth.


Engineered cylinder embedded in sand or gravel that dissipates water as quickly as it is received by transferring it to the surrounding medium.


An underground storage tank for rainwater, often drained from a roof.

“Managing Rain Drops” Resources:

Glossary/Alphabet Soup:

ACE/ ACOEArmy Corps of Engineers has authority over wetlands alteration, Rivers & Harbors Act 1899, Nationwide Permits for outfalls into navigable waters, Stormwater Management Facilities, discharges into ditches.
BMPBest Management Practices are techniques, measures or structural controls used to manage the quantity and improve the quality of stormwater runoff. The goal is to reduce or eliminate the contaminants collected by stormwater as it moves into streams and rivers.
319Section of the Clean Water Act that deals with Stormwater
Clean Water ActShort name adopted in 1972 for the Federal Water Pollution Control Act of 1948 as Amended
CRMCCoastal Resources Management Council or RI CRMC is an agency required in each state by the federal Coastal Zone Management Act. This agency regulates lands within 200 feet of the coastal feature, contiguous wetlands (including freshwater wetlands), and near-shore waters.
DEM OWR/ RIDEMRI Department of Environmental Management is delegated to implement and enforce the federal Clean Water Act by the U. S. EPA in Rhode Island. Office of Water Resources staff oversee stormwater discharge permits and related activities
DPWDepartment of Public Works is the municipal department that most often is responsible for maintenance of street drains, storm sewers, and sanitary sewers. Some towns have a Sewer Authority that interacts with DPW.
EC4The Executive Climate Change Coordinating Council was legislated under the Chafee administration and is chaired by DEM Director. It includes state agencies of Administration, Health, Transportation, Emergency Management, Energy Resources, Commerce, DEM, CRMC, and Statewide Planning.
EPAU. S. Environmental Protection Agency administers the Clean Water Act. Region 1 EPA in Boston is our local office.
Gray infrastructureSystem of pipes, pumps, and treatment to capture and remove pollutants from storm- and used-water.
Green InfrastructureSystem using natural models and materials for capturing and treating stormwater. EPA’s statement on green infrastructure
Impervious CoverAny solid surface that water does not penetrate: paved roads, bridges, parking lots, sidewalks, run-ways, and roofs
LID Low Impact Development, a nationally recognized set of principles and guidance to maintain ecosystem services in developed area promoted by EPA.
MCMMinimum Control Measures in the MS4 Stormwater program are 6 actions required of a municipality: (1) Public outreach and education; (2) public participation; (3) illicit discharge detection and elimination; (4) construction site run-off control; (5) post-construction stormwater management; (6) stormwater management for municipal operations.
MS-4Municipal Separate Storm Sewer System that is owned by a government entity or institution that is permitted to discharge pollutants into receiving waters under the NPDES/ RIPDES provisions of CWA.
NEIWPCCEstablished by an Act of Congress in 1947, the New England Interstate Water Pollution Control Commission is a not-for-profit interstate agency that utilizes a variety of strategies to meet the water-related needs of our member states—Connecticut, Maine, Massachusetts, New Hampshire, New York, Rhode Island, and Vermont.
NPDES/ RIPDES National Pollution Discharge Elimination System and its delegated form, Rhode Island PDES, is the permitting system for discharging into the waters of the United States.
NRCSNatural Resources Conservation Service is a federal agency of the U. S. Department of Agriculture that, among its many functions, educates commercial interests, hobby farmers, municipalities, and others about managing run-off and other practices to protect water.
Non-point run-offAmbient water flowing across land and constructed areas that does not come out of a pipe/ point source.
POTW/ WWTPPublically Owned Treatment Works/ Wastewater Treatment Plant.
TMDLTotal Maximum Daily Load of a specified pollutant that is a targeted threshold, allocated among the sources of that pollutant within a watershed, so that waters of U. S. do not exceed the Water Quality Standards.
WLAWaste Load Allocation is that part of the loading capacity (WQS) that is already allocated to an existing or future point source (permitted discharge).
WQSWater Quality Standards are the thresholds of physical condition and concentrations of elements or pollutants that may be discharged into waters while protecting the designated uses of that water body.