Water Resources

MS4

The MS4 (Municipal Separate Storm Sewer System) Program is a set of rules that helps control stormwater pollution in towns and cities. Local governments must get permits and create a stormwater plan to reduce pollution. These systems include things like storm drains, pipes, and ditches that carry rainwater directly to rivers and streams without being treated. The plan must include six basic actions to help keep water clean.

MS4 systems are different from combined sewer systems, where stormwater and wastewater mix and can overflow during heavy rain. There are two phases of the program: Phase I for larger cities and Phase II for smaller or growing areas. Both require communities to reduce pollution and stop illegal dumping. Tools and guides are available to help communities work together and manage stormwater more effectively.

Learn more about the MS4 program at DEP’s website and Stormwater PA.

Minimum Control Measures (MCMs)

Small MS4 communities must get permits and create a Stormwater Management Program (SWMP). The SWMP includes six important Minimum Control Measures (MCMs). These rules help communities reduce pollution, protect streams and rivers, and teach people about stormwater. Communities must educate the public, involve residents in planning, find and stop illegal pollution entering storm drains, control runoff from construction sites, manage stormwater after construction is finished, and prevent pollution from municipal operations like road maintenance and vehicle washing.

Each MCM includes Best Management Practices (BMPs), which are actions communities must follow. Public education includes sharing newsletters, websites, meetings, and outreach programs to teach people about stormwater pollution. Public involvement encourages residents to attend meetings, give feedback, and report pollution problems. Illicit discharge detection focuses on finding illegal dumping or wastewater entering storm drains and removing those pollution sources. Construction and post-construction rules require permits, erosion controls, stormwater systems, and the use of low-impact development methods to reduce runoff. Pollution prevention and good housekeeping require towns to maintain roads, storm drains, parks, and equipment in ways that reduce pollution entering waterways. Employee training, regular inspections, mapping storm systems, and keeping records are all important parts of the program.

BMPS/SCMS

Stormwater Best Management Practices (BMPs) are ways to control rainwater runoff and keep water clean. There are two main types: non-structural and structural. Non-structural BMPs focus on prevention, like protecting natural areas, planting trees, reducing pavement, and letting water soak into the ground. These methods are usually cheaper and work best when planned before building. Simple actions like using native plants, disconnecting downspouts, and keeping streets clean can also help reduce pollution.

Structural BMPs are built systems that manage water after it rains. Examples include rain gardens, rain barrels, wetlands, ponds, and special pavement that lets water pass through. These tools help slow down water, filter pollutants, and reduce flooding. Different land uses (like homes, farms, cities, and roads) need different BMPs, but the goal is the same: reduce runoff, prevent pollution, and protect water quality.

TMLDS/PRP

The EPA and Pennsylvania DEP label rivers, streams, and lakes as “impaired” when they are too polluted to meet water quality standards. In Pennsylvania, many miles of streams and acres of lakes are impaired. To fix this, a Total Maximum Daily Load (TMDL) is created. A TMDL sets the highest amount of pollution a waterbody can handle and still stay healthy, and it guides cleanup efforts.

Some communities, especially those in the MS4 program, must create plans to reduce pollution. These include TMDL plans and Pollution Reduction Plans (PRPs). PRPs require communities to lower pollution levels such as sediment and nutrients by setting amounts within a few years using methods such as stormwater BMPs. The goal of all these plans is to reduce pollution and improve water quality over time.

PA ACT 167

Pennsylvania passed the Stormwater Management Act (Act 167) in 1978 to reduce problems caused by stormwater runoff like flooding and pollution. The law requires counties to create stormwater plans for their watersheds, and local towns must follow these plans by creating and enforcing their own rules for new development and construction.

The goal of Act 167 is to manage stormwater in a safe and natural way. It aims to protect streams, reduce flooding, keep natural water flow, and protect groundwater. It also encourages local governments to take responsibility for protecting the environment and preserving natural resources.

Green Infrastructure

Green infrastructure is a way to manage rainwater using nature instead of only pipes and drains. It uses trees, plants, soil, and other natural systems to soak up and slow down rain where it falls. The EPA says green infrastructure helps manage water and creates healthier cities. Examples include rain gardens, green roofs, planting trees, and special sidewalks that let water soak into the ground. Restoring wetlands and floodplains can also help reduce flooding.

Trees and plants are an important part of stormwater management because they help absorb rainwater, improve water quality, and reduce pollution that can flow into rivers and streams. They also provide homes for wildlife, clean the air, and help cool cities during hot weather. Native plants are especially useful because they grow well in local soil and weather and need less care. Green infrastructure is becoming more popular because it helps communities handle stormwater while also making neighborhoods healthier and more sustainable.

Floodplain Management

A floodplain is the land next to a river or stream that floods when water levels rise. Floodplains are important because they help store and slow down floodwater, clean water, and refill groundwater. They also support plants, animals, and can be used for parks and recreation. Keeping floodplains natural or restoring them helps reduce flooding and improve water quality.

Floodplain management is how communities plan and act to reduce flood damage. This includes rules for building, zoning, and land use to keep people and property safe. It requires teamwork between governments, businesses, and residents. Restoring floodplains—by planting vegetation, moving buildings away, or reshaping land—can reduce flooding and pollution in a natural and cost-effective way.

Mapping

When a community joins the National Flood Insurance Program (NFIP), it receives flood maps from FEMA that show areas at risk of flooding. These maps have improved over time, from older paper maps to newer digital versions. The most current map, called the Flood Insurance Rate Map (FIRM), is used to set flood insurance rates and guide local building rules. These maps show high-risk areas called Special Flood Hazard Areas (SFHAs), where flood insurance is usually required.

Communities must use the latest maps to manage development and reduce flood damage. If a property’s flood risk changes, updates can be requested through official map revisions. FEMA also provides online tools where people can search for their property, view flood maps, and check their flood risk.

Insurance

Flooding is the most common disaster in the U.S. and Pennsylvania. Flood insurance doesn’t stop floods, but it helps people recover after damage. Homes in high-risk areas (called Special Flood Hazard Areas, or SFHAs) are most likely to flood, but floods can happen anywhere. In fact, many claims come from outside these areas. People with federally-backed mortgages in flood zones must have flood insurance, but it is available to anyone in a community that participates in the National Flood Insurance Program (NFIP).

Flood insurance can be bought through insurance agents and may cover buildings and, if added, personal belongings. If a flood happens, people can file insurance claims and may also get government help during major disasters. Communities can lower insurance costs by following good flood management practices. Tools like elevation certificates help measure a building’s flood risk and can lower insurance rates if the building is higher above flood level.

Regulations

As part of the National Flood Insurance Program (NFIP), communities must adopt and enforce a local floodplain ordinance to stay eligible for flood insurance. This ordinance sets rules for building and development in flood-prone areas to reduce flood damage. Each community has a floodplain administrator who manages these rules. Regulations depend on how much flood information the community has, such as FEMA flood maps and flood elevation data, and must meet at least federal minimum standards.

The ordinance is enforced through permits, which are required before building in flood areas. A floodplain manager checks plans, reviews elevation data, keeps records, and makes sure rules are followed. Sometimes exceptions (called variances) are allowed, but they can increase flood risk. If a community does not follow NFIP rules, FEMA can place it on probation or remove it from the program, which can make flood insurance more expensive or unavailable.

Intergrated Water Resource Planning

Integrated water resource planning (IWRP) is a way to manage water by having different experts work together to solve water problems as a team. It looks at all parts of water systems together—like drinking water, stormwater, flooding, and wastewater—often across multiple towns or watersheds instead of just one city.

This approach helps communities find better solutions, share resources, save money, and meet environmental rules. It can also improve water quality, support better planning, and create new partnerships and funding opportunities. A related idea called “One Water” treats all water as one connected system and focuses on long-term, sustainable water management for both people and nature.

Sustainable Land Use Planning

Land development can harm water resources, but smart planning can reduce damage while still supporting economic growth. “Smart growth” focuses on building in ways that protect water quality, reduce flooding, protect groundwater, and lower long-term costs for communities. Pennsylvania uses its own version called the Keystone Principles, which encourage things like redeveloping old areas first, concentrating growth, protecting natural areas, and planning across regions.

Communities use tools like comprehensive plans, zoning, and local ordinances to guide development. Low Impact Development (LID) uses natural methods like rain gardens, green roofs, and permeable pavement to manage stormwater where it falls. Other approaches include hazard mitigation planning, EcoDistricts, and rules for stormwater and floodplains that protect people and natural areas. Individual property owners can also help by protecting natural land, planting buffers near streams, and using conservation easements to preserve open space.

Transportation Planning

Land development can harm water resources, but smart planning can reduce damage while still supporting economic growth. “Smart growth” focuses on building in ways that protect water quality, reduce flooding, protect groundwater, and lower long-term costs for communities. Pennsylvania uses its own version called the Keystone Principles, which encourage things like redeveloping old areas first, concentrating growth, protecting natural areas, and planning across regions.

Communities use tools like comprehensive plans, zoning, and local ordinances to guide development. Low Impact Development (LID) uses natural methods like rain gardens, green roofs, and permeable pavement to manage stormwater where it falls. Other approaches include hazard mitigation planning, EcoDistricts, and rules for stormwater and floodplains that protect people and natural areas. Individual property owners can also help by protecting natural land, planting buffers near streams, and using conservation easements to preserve open space.

Climate Change

Climate change means long-term changes in weather patterns over many years. One major effect is more frequent and stronger storms, which can increase flooding, stormwater runoff, and soil erosion. Water managers are planning for these changes because they affect rivers, streams, and drainage systems.

To respond, communities use strategies that reduce runoff and flooding. These include green infrastructure, low impact development, and reducing paved surfaces like roads and parking lots. Other actions include protecting wetlands and floodplains, planting trees and native plants, restoring stream buffers, and improving sewer systems to prevent pollution during heavy rain.

Watershed Information

A watershed is an area of land where all rainwater and groundwater flow into the same stream, river, lake, wetland, or ocean. Large watersheds are called basins, while smaller ones are called sub-watersheds. Watersheds can cross city, county, and state borders.

The United States Geological Survey groups watersheds using Hydrologic Unit Codes (HUCs). These codes help identify different watershed sizes. Smaller HUC numbers mean larger watersheds, while larger HUC numbers mean smaller watersheds. In Southwestern Pennsylvania, the four main HUC-04 watersheds are the Allegheny River Watershed, Monongahela River Watershed, Ohio River Watershed, and part of the Susquehanna River Watershed.