Recap of 10-17-19 Westover Flood Meeting / Outstanding Questions

By Suzanne Sundburg

October 24, 2019

On Thurs., 10-17-19, four civic associations (Highland Park-Overlee Knolls, Leeway Overlee, Tara Leeway Heights and Westover Village) in the Torreyson Run watershed (the Westover area) met w/county staff Mike Moon (DES), Demetra McBride (bureau chief of the Office of Sustainability and Environmental Mgmt.) and County Board Chair Christian Dorsey.

The meeting was civil but contentious. Many audience members audience expressed frustration and anger.

One woman had contacted the county to report severe flooding at her house 2 years ago (2017), and county staff had ignored her pleas for help.

Though staff stated that government alone could not resolve the flooding problem, there is little on an individual basis that a homeowner can do to prevent 8 feet of water from flooding a basement. Flooding of that level can’t be corrected by landscaping changes made to a homeowner’s lot; it requires county intervention.

Staff touted the Small Business Association (SBA) loans that the county had made accessible to flood victims. Whereas SBA loans are useful, they are loans. Residents can’t keep on borrowing to repair damage or make expensive landscaping adjustments when they can’t be sure they won’t get wiped out again in 5 days, 5 months or 5 years.

Attendees asked about additional relief funds to assist flood victims in the future.

Attendees understood the county’s argument that stormwater infrastructure (man-made/gray infrastructure) planning and execution will take time, but they also are desperate because flooding will happen again if the county continues to delay in taking active steps to remedy the problems.

Staff explained that even if the money were available, it simply wasn’t feasible to add enough pipe capacity to handle a storm of the intensity of the one on 7-8-19. Roads would have to be closed for extensive periods, homes and structures were in the way.

The one point of agreement was that these microburst storms will continue increasing in frequency and intensity. Moreover, similarly intense storms have occurred in the past, especially in 2006 and 2018, though July 8 was the most intense rainfall over a very short period of time (20 to 30 minutes).

[Note: For reference, below is a chart listing the top 10 events ranked by rainfall intensity, as recorded at National Airport.]:

DCA Top 10 Max Hourly Precipitation Events 1963-2019

DCA Top 10 Max Hourly Precipitation Events 1963-2019

An audience member expressed concern about the county’s overstating the rainfall intensity on July 8, and he questioned the 9 inches/hour that staff was repeating. Staff claimed that North Arlington had received more intense rainfall than the 3.3 inches/hour reported at National Airport.

Staff stated that it had referred to a NOAA weather gauge, which indicated that 4.4 inches of rain had fallen in roughly half an hour in North Arlington (they had not used informal figures reported by Weather Underground). Staff then used the 4.4-inch figure to extrapolate the rainfall intensity in hourly terms, or roughly 9 inches. [However, the total rainfall over the 3-hour period on July 8 totaled 3.41 inches:]

Staff agreed to provide a report on the rainfall intensity and other data it has been collecting.

Staff tried to side-step responsibility, saying that development wasn’t the cause of the severity of damage — it was rainfall intensity, for which the system wasn’t designed. The increase in impervious surfaces in the Torreyson Run watershed was 3%, but staff offered no frame of reference (the length of time over which this increase has occurred or how it was calculated).

Nonetheless, attendees continued expressing concern that the county was dismissing the impact of redevelopment (loss of trees, land disturbance/regrading and increases in impervious surfaces) in amplifying the catastrophic level of flooding.

Residents’ viewpoint is consistent with that of many experts:

Poor stormwater management can be a significant factor in many localized flooding events, increasing damage to property and public infrastructure. Federal Emergency Management Agency (FEMA) estimates that 25% of the $1 billion in annual damages caused by flooding are linked to stormwater.[5] By increasing infiltration and retention, green infrastructure can substantially reduce the overall amount of water entering local storm sewers or surface waters and reduce flooding-related impacts, including decreased property values and tax revenues associated with flooding, damages to public infrastructure and associated repair costs and damages to private and public property.

Urbanized land amplifies flooding. Typically, we focus on rainfall rates and how fast the system was moving in the aftermath of a flood. However, one of the most important aspects of an urban flooding event is the presence of “impervious surfaces” like roadways, parking lots, and so forth. Brian Bledsoe is the director of the Institute for Resilient Infrastructure Systems at the University of Georgia. He is also a professor of civil and environmental engineering. Bledsoe opined in the Washington Post:

“Most of us intuitively grasp that intense rainfall interacts with increases in impervious surfaces such as roads, sidewalks, parking lots and rooftops to amplify the volume and speed of storm runoff. We are less inclined to think about where the water goes from there — how flood mitigation measures like ponds and detention basins can become less effective over time or fail if not properly maintained, or how the ability of streams and rivers to carry runoff changes due to sediment movement and other natural processes. It’s not just the rain that can change. It’s the rain, the urban footprint and the drainage systems all changing together.”

One person asked for the county to revisit the redevelopment plans for the Reed School site, which included the loss of very large mature trees (including 1 over 4 feet in diameter) and the increase in impervious surfaces (6%) to see if more could be done to reduce the project’s stormwater impact.

Staff claimed that Virginia’s Dillon Rule prevented Arlington from preventing removal of trees on private property. Westover resident Audrey Clement countered that the county was an irresponsible steward of public land, referring to a list showing the loss of 900+ trees in just 9 public projects over 4 years.

Attendee Suzanne Sundburg added that there were a number of options that could help staff better protect trees on private property, but that the county had thus far refused to consider any of these alternatives.

Staff replied that the Urban Forest Master Plan was in the process of being updated, which would include input from the urban foresters in the Dept. of Parks and Recreation (DPR) and would be helpful. Attendee Suzanne Sundburg noted that DPR was one of the worst offenders with respect to tree removal on public sites. DPR evades County Administrative Regulation 4.4’s environmental assessment requirements for many of its 70+ park projects — essentially adding impervious surfaces and cutting down mature trees in vulnerable areas prone to flooding with little or no accounting of the environmental damage.

Christian Dorsey did comment that the county had become “lazy” in thinking that planting 3 trees to replace the loss of a mature tree was a sufficient “replacement” — acknowledging that equivalent environmental benefits (including stormwater management) of newly planted trees wouldn’t be fulfilled for another “40 years.”

Additional questions that could/should be posed:

1) How often are storm sewer pipes, catchments and related stormwater infrastructure inspected and cleared? Though staff discussed the annual inspections of stormwater detention infrastructure required for new single-family homes, a 2007 County Board work session presentation showed that the county’s inspection schedule of pipe conditions was on a 40-year cycle, with catchment basins being cleaned only once every 2 years. The FY2009 budget notes that reducing the 40-year inspection cycle to a 20-year cycle was a “priority,” but it is unclear what the inspection cycle is today.

It is also unclear whether or to what extent clogs/debris contributed to the flooding on July 8 or whether pipes and other infrastructure have been cleared of any debris subsequently left by the July 8 flood. The county also has indicated that it will reduce street sweeping efforts — a measure designed to reduce the amount of debris that goes into the storm sewer system.

2) What else could Arlington do to improve flood resilience under existing authority from state and federal governments? Arlington already has a Four Mile Run Flood Control Agreement with the U.S. Army Corps of Engineers (USACE) under which Arlington is required to limit “post-development peak runoff” to prevent increases in the “100-year peak flow” of Four Mile Run. Compliance with the federal Flood Control Act of 1965 was mentioned in older county code (Stormwater Detention) but that language has since been removed.

Typically, federal law/regulation supersedes state law, including limitations under the Dillon Rule. Are there other existing federal laws or regulations that could give Arlington greater flexibility to strengthen its stormwater management regulations and flood resilience plans?

3) How is Arlington coordinating with the USACE $3.5 million study on coastal flooding, which includes sites in Arlington County, whose goal is “to reduce coastal flood risk to people, properties, critical infrastructure, and important services and resources in the study area, all while considering future climate and sea level change”? See

4) Has Arlington already taken the necessary steps to adopt more stringent stormwater management rules, as permitted under the Code of Virginia? If not, when will Arlington seek this additional flexibility? Code of Virginia § 62.1-44.15:33 permits localities “to adopt more stringent stormwater management ordinances than those necessary to ensure compliance with the [State Water Control] Board’s minimum regulations” in order to address “excessive localized flooding.” See

What, if any, other statutory flexibility is Arlington seeking in Richmond (either from the legislature or from state regulatory agencies) to improve its stormwater management capabilities and reduce its flood hazard risk?

5) In Arlington’s development of its new Risk Assessment and Management Plan (RAMP), will Arlington update its 2004 Four Mile Run Flood Risk Analysis? See

6) When will FEMA update Arlington’s Flood Insurance Rate Maps (FIRMs), which define Arlington’s floodplains?Current FEMA maps do not take into account the impact of climate change or sea level rise: Could or should Arlington initiate a map revision to better reflect Arlington’s current hydrological conditions? See

7) Has Arlington reviewed either of the resources below to determine whether either may contain additional suggestions or pathways to improve Arlington’s flood resilience?

Resource: Georgetown Climate Center, 2010 Virginia Case Study — Stemming the Tide: How Local Governments Can Manage Rising Flood Risks

Resource: College of William & Mary Law School — 2018 Sea Level Rise and Recurrent Flooding: A Toolbox for Local Governments in Virginia

8) When can the public expect to see revised regulations governing land disturbance and land disturbance permits, which staff has stated are in process?

9) How/when will Arlington integrate more accurate and current data regarding the loss of mature tree canopy in its stormwater runoff calculations and projections, in its flood analyses and mitigation plans, and in its stormwater management plans and policies?

10) When will Arlington review existing plans for park projects (not yet under construction) to identify greater stormwater runoff-reduction and flood mitigation options that could be integrated into these projects, since much of Arlington’s parkland was acquired specifically for this purpose?

According to the current Stormwater Master Plan:

The original master plan [adopted in 1958] described the relationship of runoff to land use change and recommended a number of proposed drainage improvement measures. One of the plan’s most significant recommendations was to encourage floodplain land acquisition to avoid flooding in areas near streams. This recommendation led to the acquisition of parkland along most County streams and was the basis for a number of the parks adjacent to Lubber Run, Four Mile Run, Gulf Branch, Donaldson Run, Doctor’s Branch and Windy Run. p. 3, 2014 Stormwater Master Plan,

11) Would Arlington be willing develop prescreened lists of qualified contractors (with confirmed license status, insurance, BBB standing, etc.) to help property owners select legitimate landscaping and flood-damage remediation companies?