Maryland

Maryland Stormwater Design Manual

StateMarylandhighNo

Open source PDF ↗Official agency page ↗

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Document Metadata

Jurisdiction level

state

“State of Maryland”
TOC-3

State

Maryland

“State of Maryland”
TOC-3

Version / edition

Volume One

“VOLUME ONE”
TOC-1

Adoption / effective date

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Last revised date

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Relationship to state manual

independent

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Design Criteria

Design storm return periods (years)

1-year, 2-year, 10-year, 100-year

“Rainfall Depths Associated with the 1,2,10 and 100-year, 24-hour Storm Events”
2.11, Table 2.2

Water quality volume method

WQv is calculated as (P)(Rv)(A)/12, where P is the rainfall depth (1.0 inch in the Eastern Rainfall Zone, 0.9 inch in the Western Rainfall Zone), Rv is the volumetric runoff coefficient (0.05 + 0.009 * I), and A is the site area in acres.

“WQv = (1.0) (Rv)(A) Eastern Rainfall Zone ... WQv = (0.9) (Rv)(A) Western Rainfall Zone ... where: WQv = water quality volume (in acre-feet) Rv = 0.05 + 0.009(I)”
2.2, Section 2.1

Peak flow calculation method(s)

TR-55, TR-20

“The models TR-55 and TR-20 (or approved equivalent) shall be used for determining peak discharge rates.”
2.10, Section 2.3

Required hydrologic/hydraulic software

TR-20, TR-55

“TR-20 Technical Release No. 20 Project Formulation-Hydrology, computer program TR-55 Technical Release No. 55 Urban Unit Hydrology for Small Watersheds”
1.21, Table 1.3

Approved BMP categories

Stormwater Ponds, Stormwater Wetlands, Infiltration Practices, Filtering Systems, Open Channel Practices, Non-structural Practices

“Acceptable BMP groups are: - Stormwater Ponds - Stormwater Wetlands - Infiltration Practices - Filtering Systems - Open Channel Practices - Non-structural Practices”
1.16, Section 1.3.1