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Flood Mitigation Plan

After experiencing two historic floods in less than two years, Ellicott City was in desperate need of plan for flood mitigation that protects public safety, provides a sense of security to businesses, residents, and property owners, and retains the city's historic charm. 

Upon taking office in December 2018, County Executive Calvin Ball immediately directed the Department of Public Works (DPW) to develop options for flood mitigation using those values as guiding principles. Utilizing the information provided in the 2016 Ellicott City Hydrology/Hydraulic Study, DPW worked with the author of the report to reanalyze potential projects to see how to most effectively reduce the amount of water on the street on Lower Main Street and the West End while preserving as many buildings as possible. 

After analyzing over 70 potential scenarios, the county executive selected the five options that best achieve the desired outcomes to present to the community for comment and discussion. The community was given an opportunity to comment on these options via email, the website, or at a public meeting on May 2nd.
After reviewing the comments and conferring with experts, County Executive Ball selected option 3G.7.0. This bold plan is the best available option to move forward with urgency, prioritize public safety, and build a model of resilience.  
This was eviewed by a national team of experts assembled by the Army Corps of Engineers. In their report, the Army Corps affirmed that the county is following a sound process and that the projects included in the county's plan can significantly reduce flood risk to Historic Ellicott City. 

Ellicott City Safe and Sound
Flood Mitigation Projects


Water Depths Comparison

*Average depth from Caplan's to Maryland Avenue during July 2016 storm conditions.

*Maximum depth reflects water depths on Lower Main Street above Maryland Avenue. 

Water Velocity


Values generated using the 2016 storm

Frequently Asked Questions

  • Why do we need the Safe and Sound Stream Debris Removal Program?
    Areas that experience flooding during major rain events may benefit from the removal of debris in nearby streams. Excess stream debris can cause localized flooding when constriction points along the stream become blocked by debris and cause a backup of water onto roads and other infrastructure. The most common constriction points are the undersides of bridges and culvert openings. Culverts are the pipes and concrete structures that carry streams under roads. When these blockages occur, the resulting flooding can create a threat to human safety, personal property, public infrastructure, and the environment. Stream Corridor Assessments completed by S & S Planning and Design after the 2011 and 2016 floods in Ellicott City documented debris blockages as contributors to flooding and recommended that a debris management program be instituted. Channel maintenance for debris has been ongoing on the Hudson Branch in Ellicott City since 2015 and is now being expanded in both geography and frequency. To minimize the risks associated with stream debris, Howard County is sending Howard EcoWorks into nine flood-prone streams after qualifying weather events to assess for accumulation of debris, determine what is appropriate to remove, and then remove debris that has the potential to contribute to localized flooding.
  • What is stream debris?
    In this context, stream debris is anything within the stream or immediately along its banks that threatens to move downstream during high flow events and has the potential to clog culverts or other constriction points, which can result in local flooding. This may include logs, branches, trash and/or other bulk material.
  • Where is stream debris being removed?
    Debris is being assessed, and removed if needed, at dozens of sites on public properties and on Columbia Association property along nine Howard County streams. These sites have been chosen because they are locations that are known to experience, or contribute to, localized flooding.
  • What if I see debris that could create a blockage in an area not covered by this program?
    Please report such debris using the County’s “See, Click, Fix” application, linked here:
  • When is the debris removed?
    Debris will be removed after any rain event of 2” or greater accumulation in a 24-hour period, or after an hour of sustained winds over 30mph. Within three business days of a qualifying wind or rain event, each of the locations will be inspected for accumulation of debris and need for removal. Within fourteen business days of the inspection, the material that was identified for removal during the inspection will be removed.
  • Who is identifying and removing the debris?
    Debris will be identified and removed by Howard EcoWorks or the County Bureau of Highways.
  • Why don’t inspection crews remove debris immediately after identifying an accumulation?
    Inspection results are analyzed before removing material because some locations may have a more immediate need for removal than others, based on stream conditions, threat to property or infrastructure and weather forecasts.
  • Why are the results reported as “cubic yards of debris removed”?
    While weight of debris could be used to track this effort, volume (the space that an object occupies) is what really causes backups at constriction points such as culverts and bridges. For example, while millions of tiny steel ball bearings may weigh more than all the woody debris removed from a stream, they would not cause as severe of a backup as less dense, but larger, woody debris. A cubic yard can be visualized by picturing a cube that is 3 feet long, by 3 feet wide, by 3 feet deep. The bed of an average full size pickup truck, full but not piled higher than the edges of the bed, will hold 2.5 cubic yards of material.
  • Why has the debris been left as a pile along the side of the road?
    The County or Howard EcoWorks may need to temporarily stage debris along the side of the stream or road for later pickup due to vehicle availability and amount of debris. These piles will be removed within the fourteen business day timeframe that begins immediately following a significant wind or rain event. Click here to review a flow chart of the stream debris removal process.
  • Why is debris being removed only from public property and CA property?
    To begin this process as quickly as possible, public properties have been selected because access to private property relies on the permission of private landowners which often takes several months for the County to acquire. Pre-existing agreements between Columbia Association and Howard County provide the County with access to Columbia Association’s private parcels, without necessitating the process of acquiring permission to enter individual parcels.
  • How will the County and Howard EcoWorks determine what debris to remove?
    Priority debris for removal includes 1) debris within and immediately upstream of culverts or other areas of constriction, 2) debris that has the potential to mobilize during an event and create a blockage downstream and 3) debris that otherwise poses or may pose a risk to adjacent infrastructure. Debris is typically composed of fallen trees and logs and may also contain smaller branches, overhanging branches and vines and trash / bulk material. Consideration for removal is given to the size of the debris relative to downstream constrictions, potential for the material to mobilize or create a hazard during a storm event and the location of the debris in stream bed or on the stream bank. The area of inspection is up to approximately bankfull elevation. The bankfull elevation is the same as the ordinary high water mark (OHWM); in many channels this is the point where water begins to flow out onto its floodplain. If stream banks are armored, live, overhanging branches <3” in diameter will be removed. If stream banks are unarmored, trees and limbs <12” in diameter will be removed if they are considered priority as defined above.
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