Stormwater Management Division

Mark S. Richmond, Chief

Mission Statement

The mission of the Stormwater Management (SWM) division is to advance the quality of life for the citizens of Howard County through the improvement and management of the quality and quantity of water that originates in, falls onto, or passes through the county on its way to the Chesapeake Bay.

The SWM division will accomplish this by:

  • communicating to the public the value of clean water and the ways they can personally improve water quality,
  • monitoring and maintaining our public and private storm water facilities,
  • planning, implementing, and maintaining a program for good water resource management,
  • partnering with individuals, citizen volunteers, local environmental groups, businesses, schools, and other government agencies in an effort to promote beneficial water quality management,
  • responding to public inquiries and complaints in a courteous and timely manner, and
  • evaluating and implementing technologies consistent with stormwater best management practices (BMP's).

MDE Discharge Permits for Vehicle Washing

Maryland Department of the Environment (MDE) requires a permit for the discharge of any quantity of wastewater to ground and surface waters. Vehicle wash water is considered to be wastewater and therefore onsite vehicle washing requires a permit. Companies that perform outdoor vehicle washing have three options for managing the wastewater they generate:

    1) Discharge wastewater to the sanitary sewer (please contact the Bureau of Utilities at 410-313-4943 for more information),
    2) Contain, collect and transport wash water off-site for appropriate treatment and disposal, or
    3) Obtain an MDE discharge permit to discharge to the ground and surface waters (Call the MDE Wastewater Permits Program at 410-537-3778).

Please go to the following links below for more information:

Little Patuxent and Middle Patuxent Watershed Assessment

The Howard County Department of Public Works has undertaken a comprehensive watershed assessment within the Middle Patuxent River and the Little Patuxent River watersheds. The watershed assessment was performed to create an inventory of the natural resources as well as existing problems (erosion, trash, lack of wooded stream buffers, etc.) within these watersheds. Another result of the assessment is a list of potential projects that can be done to protect and restore these resources, address the problems, and ultimately improve water quality in our County streams and water bodies.

This assessment measured current environmental conditions and identified opportunities for restoration projects to be included in the capital budget. These projects will improve water quality in the County’s streams and rivers as well as the Chesapeake Bay. Potential projects investigated include stream restoration, adding water quality treatment to existing stormwater management ponds, constructing new stormwater management facilities, performing reforestation, and stabilizing existing storm drain pipe outfalls.

Due to the large overall study area, the field work was conducted in four distinct areas -- Northern Little Patuxent, Southern Little Patuxent, Northern Middle Patuxent, and Southern Middle Patuxent watersheds as depicted on the Little and Middle Patuxent Watershed Map. The County conducted a public meeting in each of the four study areas to report on the findings of field work results, to describe the next steps in the assessment study, to review possible restoration techniques, and to discuss the status of its countywide plan for meeting Chesapeake Bay Total Maximum Daily Load (TMDL) goals. Crews of two or three County employees or consultants conducted the field assessments, which entailed performing visual observations, taking photos, preparing sketches, and entering the data into handheld field tablets.

The results of the field assessments were used to score and rank the potential project sites, and concept plans were developed for the highest rated 148 sites. A report was generated for both the Little Patuxent and Middle Patuxent watersheds, which includes the study methodology, results, and the concept plans. Some concept plans are on private properties; however, these potential projects will only move forward with the permission of the property owners. These reports are available through the following links:

Little Patuxent Watershed Report
Middle Patuxent Watershed Report

If you have any specific questions or concerns or would like additional information regarding the watershed assessment, please contact the County by emailing Christine Lowe at or calling 410-313-6444.

Past meeting presentations:

June 17, 2015 - Southerm Middle Patuxent Watershed
June 22, 2015 - Northern Little Patuxent Watershed
June 24, 2015 - Southern Little Patuxent Watershed
June 30, 2015 - Northern Middle Patuxent Watershed
December 2, 2015 - Northern Middle Patuxent Watershed
December 3, 2015 - Southern Little Patuxent Watershed
December 9, 2015 - Southern Middle Patuxent Watershed
December 10, 2015 - Northern Little Patuxent Watershed

Patapsco and Mainstem Patuxent Watershed Assessment

Having completed the Little Patuxent and Middle Patuxent Watershed Assessment as noted above, the County has begun another watershed study for the remainder of the County. This study includes the Patapsco River and Mainstem of the Patuxent River watersheds. The study purpose and methodology are the same as the Little Patuxent and Middle Patuxent watershed assessment. Due to the large overall study area, the field work is being conducted in five distinct areas – South Branch Patapsco River, Lower North Branch Patapsco River, Brighton Dam/Triadelphia Reservoir, Rocky Gorge Reservoir, and Patuxent River Upper watersheds. Field assessments for this study were completed in April through May 2016.

(Click on the map for a larger image)

Public Meetings:
The County welcomes public participation in the development of the watershed study. The County conducted public meetings in Summer 2016 to report on the findings of field work results, to describe the next steps in the assessment study, to review possible restoration techniques, and to discuss its countywide plan for meeting local and Chesapeake Bay Total Maximum Daily Load (TMDL) goals.

Public Meeting Presentations:

June 21, 2016Rocky Gorge Reservoir and Upper Patuxent River Watersheds

June 23, 2016Lower North Branch Patapsco River Watershed

June 28, 2016South Branch Patapsco River and Brighton Dam/Triadelphia Reservoir Watersheds

Please continue to watch this area for updates on the watershed assessment study and for fall public meetings. Meeting dates and locations for the Fall 2016 public meetings will be advertised when the schedule is finalized.

If you have any specific questions or concerns or would like additional information regarding the watershed assessment, please contact the County by emailing Christine Lowe at or calling 410-313-6444.

Zika Awareness

Stormwater management facilities help remove pollutants from water and prevent flooding in our community. In order to do so, some of these facilities must temporarily or permanently retain water. If stormwater facilities are designed and maintained correctly, mosquito populations should not be a concern. Learn more on Stormwater Facilities and Mosquitoes webpage.

The Howard County Health Department has posted information regarding the Zika Virus. Please visit

Countywide Implementation Strategy (CIS)

On December 18, 2014, Howard County received a new National Pollutant Discharge Elimination System (NPDES) Municipal Separate Storm Sewer System (MS4) Discharge Permit from the Maryland Department of the Environment (MDE). The County's MS4 permit includes requirements for watershed restoration activities, specifically preparation of a restoration plan within the first year of the permit term. To address this requirement, Howard County has developed a Countywide Implementation Strategy (CIS). 

NOTE: The costs shown to implement the Financial Assurance Plan to meet the stated goals of the plan have been estimated. The cost estimates provided in the CIS will likely adjust as the County progresses with implementation of it program. Learn more about CIS.

Downtown Ellicott City Flood Study

A detailed floodplain analysis using both one-dimensional and two-dimensional hydraulic modeling is available for viewing. The floodplain study, which was completed in July 2013, considered several standard rainfall events as well as the rainfall event that resulted from the remnants of Tropical Storm Lee on September 7, 2011. The study also included a conceptual assessment of potential flood mitigation options.

  • Floodplain Study Report
  • Inflow Hydrograph Comparison
  • Rainfall Intensity Distribution Comparison
  • Cumulative Rainfall Distribution Comparison
  • Flooding Depth and Limits – Multiple Storm Events
  • Conceptual Mitigation Options
  • Appendix A - Existing Hydrology and Hydraulics
  • Appendix B - Concept Designs
  • Appendix C - Proposed Hydrology and Hydraulics
  • Appendix D - 1-D Hydraulic Modeling (HEC-RAS)
  • Appendix E - 2-D Hydraulic Modeling (TUFLOW)
  • Appendix F - Center for Watershed Protection SWM Concept Analysis

  • The Howard County Flood Mitigation Plan 2013 Progress report is available for viewing here.

    The Tiber-Hudson and Plumtree Branch Stream Corridor Assessment is a visual survey of the stream corridor to document conditions that potentially affect flood conditions. Also see the supplemental Case Study: Valley Mede-Ellicott City Tropical Storm Lee Flood Event

    Ellicott City Retaining Walls Inspection Report (May 2016) – Stream Walls

    An above-water visual condition inspection of all the retaining walls located along the Hudson Branch and Tiber Branch in Old Ellicott City, MD was conducted in Spring of 2016. The purpose of this inspection was to assess the current condition of the walls and provide a tool for prioritizing the repair of the inspected walls.

    Ellicott City Retaining Walls Inspection Report – Stream Walls

    Rain Barrels

    This is the seventh year that University of Maryland Extension Master Gardeners and Howard County have partnered to offer residents free barrels to turn into rain barrels. Howard County residents are eligible to receive a free 55-gal. plastic barrel with cut-outs for fittings, to be used for a rain barrel (one free barrel per address, please). Residents must buy fittings and assemble the rain barrels. Rain barrel must be used in Howard County.

    Recipients of the barrels must fill out pledge form and take part in a short volunteer-led workshop. Workshops are ongoing, 9 am – 11 am on the first and third Saturday, from April 2, 2016, through October 15, 2016 at the Alpha Ridge Landfill (2350 Marriottsville Rd). The workshops are held at the gazebo, just inside the entrance to the landfill.

    Dates for 2016 Barrel Giveaway to “Make Your Own Rain Barrel” will be April 2, May 7, May 21, June 4, June 18, July 16, Aug 6, Aug 20, Sept 3, Sept 17, Oct 1, Oct. 15. There will be no workshop on April 16 (GreenFest) or July 2.

    Watershed Protection and Restoration Fund

    Learn more here

    MS4 NPDES Permit Annual Update Number 20

    In accordance with Howard County's Municipal Separate Storm Sewer System (MS4) National Pollutant Discharge Elimination System (NPDES) Permit (Number MD0068322, 00-DP-3318), the County must prepare Annual Updates to report on the progress made during the preceding permit year. Progress is reported on compliance with pollutant source identification in stormwater runoff; water quality impacts; discharge characterization; management programs; watershed assessment and planning; watershed restoration; assessment of controls; program funding; Total Maximum Daily Loads (TMDLs); and special programmatic conditions. The County submitted the Annual Update for its 20th permit year to the Maryland Department of the Environment (MDE) on December 18, 2015. To view the County’s Annual Update Number 20 and the supporting databases, click here.

    Howard County Code