In last week’s column, I explained why Arlington is not ready for a major flood.
On Saturday, December 10, the County Board approved zoning changes to S-3A zoning districts without the safeguards against flood risk that I recommended in that column.
Commenting on my earlier column, Arlington environmental activist Suzanne Sundburg noted County Manager Mark Schwartz’s admission (at December’s Arlington County Civic Federation meeting) that no one in Arlington County government has been assigned the responsibility of assessing Arlington’s cumulative flood risk.
Mr. Schwartz’s failure to assign anyone this important task means that no one is weighing or producing public analyses that encompass ALL of the dynamic factors that can increase flood risk, including:
- Land use changes and increases in impervious and semi-pervious surfaces;
- Climate change, including sea-level rise and higher tides in the Chesapeake Bay, Potomac River and therefore, the Four Mile Run watershed;
- Other existing floodplains and historically flood-prone areas;
- The limitations of storm-water management systems for flood-reduction purposes;
- The loss of Arlington’s mature tree canopy, etc.
The more development and the more pavement (aka “impervious surfaces”) added to public parks (including FEMA floodplains, flood-prone areas, Chesapeake Bay resource/riparian protection areas and other portions of our watershed), the greater the risk of flooding.
Arlington’s lack of a “flood czar” and its lack of a comprehensive flood-risk assessment means that we are gambling with the lives and property of Arlington citizens and business owners. The County itself also risks damage to or loss of its own critical infrastructure and assets.
Ms. Sundburg also has asked whether County staff has or can obtain updated local stream gage measurements to supplement those found in a 2004 document: Flood Frequency Analysis for Four Mile Run at USGS Gaging Station 1652500, now almost 13 years old. Updated local measurements may be useful in assessing Arlington’s current flood risk.
A recent Texas A&M study suggests that even in the absence of climate change, cities and urban areas are facing an increased flood risk. So discounting the added impact of climate change doesn’t negate the increasing flood risk that Arlington and other urbanized communities are facing.
Remnants of a 2011 tropical storm that hit us wouldn’t be considered a “100-year rainfall event.” Yet, this storm was sufficient to cause significant localized flooding along Four Mile Run. You can see it in action in this YouTube video.
And the mere presence of flood-protection improvements made in the downstream and upstream Four Mile Run watershed since Hurricane Agnes in 1972 coupled with the fact that Arlington has not suffered comparable flood damage since Agnes are NOT confirmation that those improvements offer sufficient flood protection in today’s environment.
In truth, we have no reliable basis on which to be certain whether these post-1972 improvements are sufficient because:
- Arlington lacks a flood czar to evaluate them, and
- We haven’t had a storm comparable to Agnes since the 1970s.
The County Board should direct the County Manager to:
- Appoint a flood czar;
- Direct that czar to prepare and make available for public review and comment a comprehensive flood risk assessment; and
- Direct that czar to prepare and make available for public comment a flood mitigation plan for Arlington similar to the Westchester County Plan that I discussed in last week’s column.