Stormwater Management Solutions

What is it?

Stormwater management solutions, in the context of adaptation and resiliency, can come in a variety of forms and several techniques can often be combined in one project. These type of measures can be categorized as “green infrastructure” and examples include pervious pavement, bioswales and bioretention. Where proper attention is paid to infiltration rates and the flows created by storms, green infrastructure can help achieve environmental goals without negatively affecting passengers.

Related Sections of the Toolbox:

Stormwater Maintenance Practices

What assets can be protected?

Pervious Pavement

Permeable pavements have spaces for air and water to pass through; the spaces allow water to infiltrate into the ground, reducing runoff. More specialized forms of porous pavements include interlocking concrete pavers, in which water drains through the gabs between precast blocks, and grass or gravel pavers, in which fill material is laid on top of a plastic grid. Permeable pavements also have cooling properties due to evaporation and reduced heat storage. Applicable uses include sidewalks, parking lots and alleys. MDE design requirements include: must provide reservoir storage for the 1 yr storm; must provide drainage for the 10 yr storm; soil infiltration rate must be greater than/equal to 0.52 in/hr; bottom of storage reservoir must be a min. of four feet above the seasonal high water table.

Advantages/Disadvantages

Advantages – useful when limited space available for stormwater management; lessens amount of impervious surface; cost effective; MDOT SHA has extensive specs, design requirements, etc. available for reference

Disadvantages – lower structural strength (not suitable for roadways/streets); routine maintenance required: surface maintenance requiring the removal of trash and sediment/organic debris removal, winterization; vacuuming structures, removing fine sediments and debris annually; cannot apply de-icers or sand; requires suitable soil

Bioswales

Bioswales are linear strips of land that is sloped on both sides and filled with vegetation used to transmit runoff at a slower pace to help minimize erosion. Incorporation of bioswales/green infrastructure is included in MDOT MTA’s 2019 Bus Stop Design Guide.

Where proper attention is paid to infiltration rates and the flows created by storms, green infrastructure at transit stops can help achieve environmental goals without negatively affecting passengers.

Advantages/Disadvantages

Advantages - less right-of-way required; good for erosion/sediment control; Green infrastructure helps the state/local governments meet environmental goals, which include improving water quality, reducing loads on water treatment systems, and protecting natural habitats

Disadvantages – sediments and pollutants can be re-suspended if slope and vegetation are not maintained; maximum drainage area is 1 acre; routine maintenance required: surface maintenance requiring the removal of trash and sediment/organic debris, removal of invasive species, moving of grass, pruning, and watering of vegetation; public may have negative perception of bioswales due to mosquitoes

Bioretention

Bioretention is a treatment area where runoff is filtered and infiltrated into the ground fully or water is filtered partially discharged out of the area slowly. This treatment area can serve multiple purposes: being used as a garden, pathway to other treatment systems and habitat for wildlife.

For information on specific design criteria, go to Maryland's Stormwater Design Manual.

Advantages/Disadvantages

Advantages - replenishes groundwater; can be landscaped to match surrounding area

Disadvantages – maximum drainage area is 20,000 square feet; routine maintenance required: pruning, trash and sediment/organic debris removal, watering vegetation