Stormwater Management

What is Stormwater Management?

In order to understand what stormwater management is, we need to understand what is stormwater. Stormwater is generated from rainfall or snowmelt that flows over land and into local waterbodies. In urban areas and areas with high percentage of impervious surfaces (i.e., roads, sidewalks, buildings), stormwater flows soak into the ground at much lower rates than in natural areas (more undeveloped land means more ability to soak/infiltrate stormflows). Stormwater management (SWM) reduces the amount of runoff through three principles: slow it down, spread it out, and soak it in. SWM also functions to prevent litter and other pollutants from entering our waterways.

Why do we have to provide Stormwater Management?

Stormwater runoff can cause flooding to private properties and public infrastructure, as well as erode receiving stream channels. Stormwater also carries pollutants that contains various levels of sediment, hydrocarbons, heavy metals, herbicides, nutrients, and litter that can harm local waterbodies and eventually reach the Chesapeake Bay.

There are federal, state, and local regulations regarding stormwater management. Federal regulations are explained in more detail in the Queen Anne’s County Municipal Separate Storm Sewer System (MS4) web page. At the state level, the Stormwater Management Act of 2007 requires that “a comprehensive process for approving grading and sediment control plans and stormwater management plans” be established that takes into account the cumulative impacts of both and mandates the concept of Environmental Site Design (ESD) to the Maximum Extent Practicable (MEP).

In 2009 the Maryland Department of the Environment (MDE) revised the state code regulations (COMAR) to require implementation of ESD to the MEP statewide. As of May 2010, all new development projects are required to manage stormwater runoff using these practices. In 2010, Queen Anne’s County adopted stormwater management regulations, Chapter 14:4 in the County code, that align with the revised Maryland state code on stormwater management implementation. The County Code references MDE’s "2000 Maryland Stormwater Design Manual" and subsequent revisions for designers, contractors, and developers to use in the design, construction, and maintenance of ESD practices. For more on Queen Anne’s County review of ESD practices, refer to guidance and application materials in the “Forms, Documents, and Publications” webpage.

What is Environmental Site Design (ESD)?

ESD uses small-scale stormwater management practices, nonstructural techniques, and better site
planning to mimic natural hydrologic runoff characteristics and minimize the impact of land development on water resources. Refer to Chapter 5 of MDE’s 2000 Stormwater Design Manual for more on ESD.

Stormwater Best Management Practices (BMPs)

Stormwater Best Management Practices (BMPs) are techniques or methods that manage the quantity and improve the quality of stormwater runoff in a cost-effective manner. BMPs often aim to replicate natural processes and, depending on their design, can offer social, environmental, and financial benefits to neighboring and downstream residences and community of the installed BMP.

One of the main goals of a stormwater BMP is to reduce or eliminate pollution and contaminants collected by storm runoff before that runoff reaches local waterbodies. The best place to stop pollution is at (or near) the source. Once pollutants, contaminants, or unstable nutrient levels reach local waterbodies, they can threaten the health and well-being of humans, and throw the stream ecosystem into an imbalance harmful to the aquatic species and wildlife that depend on the system.

A second main goal of a stormwater BMP is to improve water storage within the watershed. Stormwater runs off at higher rates in more developed land (areas with more impervious surfaces) in comparison to more natural areas like forests, large valleys, and wetland systems, where stormwater can be stored and filtered into the groundwater. The higher rate of stormwater runoff in more developed lands can quickly overwhelm storm drains and receiving waterbodies, causing flash flooding and stream bank erosion. BMPs function to capture, retain, and filter runoff into the groundwater system, helping to reduce flooding and erosion.

Source: Weston, MA Stormwater FAQs webpage https://www.westonma.gov/253/Stormwater-FAQs

A single BMP cannot resolve all stormwater runoff issues. But every practice/facility helps alleviate the issue. BMPs work best as a network or combination of practices that together manage the quantity and quality of stormwater in your community.

BMP Maintenance Fact Sheets (MCM1)

Refer to Chapter 4 of the MDE Stormwater Design Manual for more on BMPs.

Stormwater Plans Review

The stormwater management program is administered by the Department of Public Works. Stormwater management must be addressed for all new development within Queen Anne’s County. This must be addressed by applying and receiving approval of a design plan utilizing Environmental Site Design (ESD) and/or a Best Management Practice (BMP).

For specific design requirements refer to the 2000 Maryland Stormwater Design Manual.