Regulations & Permits

Howard County Design Manual - Volume I Storm Drainage (2017 Revision)

The Howard County Design Manual - Volume I has been revised and is available for viewing. Of particular note is the revision to the 24-hour rainfall rates for all design storms used in stormwater management computations and their effective date. Other minor revisions and clarifications have also been made.


Submission of Digital Storm Drain System and Stormwater Management Data


Under Howard County’s National Pollutant Discharge Elimination System (NPDES) municipal separate storm sewer system (MS4) permit, the Maryland Department of the Environment (MDE) requires the County to annually submit all storm sewer system data and all stormwater best management practice (BMP) data, including delineated drainage areas, in geographic information system (GIS) format. To comply with this permit condition, the County has been requiring that digital design information related to BMPs and storm sewer systems be submitted with development plans as of July 1, 2017. These data will be incorporated into the County’s inventory for submittal to MDE.

Design information required to be submitted digitally includes:

  • locations of Best Management Practices (BMPs), outfalls, manholes, inlets and pipes and easements
  • delineations of drainage area to outfalls and BMPs
  • data on BMP, outfall, manhole, inlet and pipe design information (types, dimensions, materials, plan approval date, etc.)


Data can be submitted in a GIS geodatabase, as GIS shapefiles, or as AutoCAD dxf files with an associated completed Excel file. GIS format is preferred. Links to the GIS and Excel templates can be found here:

Excel Template
GIS Geodatabase
GIS Shapefiles


Countywide Implementation Strategy (CIS)