Wednesday, November 4, 2015

Recent Rains and Flooding in Frederick MD

October brought a rainstorm that cause flooding in some sections of downtown Frederick, water in basements, etc.  The Neighborhood Advisory Council (NAC) 11 invited  Zack Kershner, the Director of Public Works for the City of Frederick, to speak to residents about the recent massive rainstorms and the damage caused by them. Some residents were concerned that the city's storm sewers could not handle the water which left some streets flooded.  Mr. Kershner described the level of water that the system is design to handle. He followed up by email with a summary that I could publish, shown below.
 
"City staff have spoken with many residents regarding the flooding that occurred City-wide in early October.  To give some idea of the amount of rain that we received and the intensity with which we received it, we had about 5 inches fall in just over an hour.  A 10-year storm for comparison purposes is approximately 5-inches total over a 24 hour period.  Storm drain infrastructure is generally designed to handle the 10-year storm.  This is a City standard, but is also standard across most jurisdictions including the State highway Administration (culverts are generally designed for larger storms as the impact of the flooding could be more detrimental/life threatening).  

To give a better picture of what we experienced, the volume of water that fell per acre of land during that storm was about 20,000 cubic feet or about 130,000 gallons per acre.  Our infrastructure simply is not designed to handle that kind of flow.  We also had complaints of flooding across the City, versus localized complaints, again signifying that the issue was not blocked or failing storm drain, but a storm with an intensity beyond what our infrastructure was designed handle.  We do conduct pre and post storm event inspections to ensure that there are no blockages at the inlets.  

Generally any debris that can get past an inlet grate is easily washed down the storm drain.  There are no plans currently to increase the storm drain infrastructure throughout the entire City, the cost of such an undertaking would be extremely cost prohibitive and could not be supported by taxes or fee's.  Frederick County puts out alerts for severe weather, and the City re-posts them to our website.  You can subscribe for their alerts at  https://frederickcountymd.gov/list.aspx  

An indication of a blocked storm drain would be if the water ponding around an inlet did not recede within the hour after the storm event.  If for instance, a resident noticed that water had receded around other inlets in the vicinity of their home, but one inlet in particular sat flooded, then that would be an indicator that there may be a blockage.  If this was the case, the resident should call our DPW switchboard at 301-600-1440 and file a report."