by Carol J. Bova
HB 1774 was written to address rural stormwater issues and amended to study stormwater management practices in rural Virginia highway ditches. Why, then, does the bill direct the Commonwealth Center for Recurrent Flooding Resiliency, a group formed to help Virginia adapt to recurrent flooding and sea-level rise, to direct the study?
The Commonwealth Center was created in 2016 to study strategies for adaptation, migration, and the prevention of recurrent flooding — deemed to be caused by global warming-induced sea-level rise — in Tidewater and Eastern Shore localities. As the adage goes, to a carpenter with a hammer every problem looks like a nail. Assigning the study to the Commonwealth Center almost guarantees that HB 1774’s stormwater concerns will be viewed through the prism of sea-level rise and recurrent flooding. And that would be counterproductive because state road and ditch flooding have no connection to sea-level rise at all.
This misdirected idea comes from Lewis “Lewie” Lawrence, executive director of the Middle Peninsula Planning District Commission (MPPDC) and the behind-the-scenes force behind HB 1774. Lawrence has doggedly insisted that Virginia Department of Transportation (VDOT) drainage failures in rural counties bordering the Chesapeake Bay, like my home county of Mathews, constitute recurrent flooding. Lawrence was instrumental in writing, and then revising, HB 1774 in close association with the Virginia Coastal Policy Center of William & Mary Law School for Del. Keith Hodges, R-Urbanna, the bill’s sponsor.
Lawrence has inserted unsupported claims attributing flooding on VDOT roads to sea-level rise in at least nine MPPDC reports since 2009. In the first of these studies, which assessed the human and ecological impacts of sea-level rise upon vulnerable locations in the Middle Peninsula, he used maps indicating that one foot of sea-level rise by 2050 would inundate large portions of Middle Peninsula counties.
Those maps don’t stand up to scrutiny. In one of those reports, the 2050 map for Mathews County reports shows 6.7 miles of VDOT roads in inundated marsh and inland areas, yet fails to show the breach in the Winter Harbor barrier beach that left marshes open to the Bay since a 1978 April nor’easter.
Why is that significant? Because the Chesapeake Bay is connected to the ocean, it reflects the ocean’s high and low tides. The rise and fall of the tides varies from one location to another depending upon the depth of the water and the shape of the coastline, among other factors. Before the nor’easter, a narrow channel at the south end restricted the flow between the Bay and Winter Harbor. The breach in the barrier beach opened the marshes at the north end of Winter Harbor to the tides of the Chesapeake Bay.
The postulated 2050 inundation shown on the map is caused by one foot of sea level rise. But in real life, the daily high tides already run 1 ½ feet to 2 ½ feet, and storm-driven tides can add one or two feet more without having the depicted impact. Nearly three decades after the nor’easter, Hurricane Isabel did cause coastal and inland flooding, but its 7.9 feet of storm surge did not produce the degree of inundation shown for one foot of hypothetical sea level rise in the MPPDC’s map.
Another publication, a September 2016 MPPDC report for the Mathews County Planning Commission, references a 2013 MPPDC study done by Draper Aden Associates (DAA), the Mathews County Rural Ditch Enhancement Study, which said:
One of the primary results of the project was the reaffirmation that poor drainage due to lack of ditch maintenance and sea level rise compounds the flooding problems and flood management solutions utilized within Mathews County.
The supposed affirmation of sea level rise impact in the DAA study was based on flawed LiDAR-derived elevation numbers and an assumed 5-inch sea-level rise in 24 years extracted from the maximum estimate in a 2010 VIMS report to the U. S. Army Corps of Engineers. That VIMS report described “a total possible sea level rise of 0.12 to 0.22 inches per year in the Mathews County area,” or 3 to 5.6 mm a year. (My book, “Drowning a County,” uses 3.5 mm a year based on the Kiptopeke tide gauge trend of 3.48 mm since Mathews has no tide gauge.)
Draper Aden used 2011 Virginia Geographic Information Network LiDAR maps that show elevations of 2 feet for cultivated fields, forested areas, Route 645, and Gullwing Cove Lane — supposedly the same elevation as the marsh to the west. Yet, contrary to what one would expect from these elevations, normal high tides of two feet do not cause any movement of water from marshes and creeks into adjacent fields. Rather, fresh water floods across the roads because it is unable to flow through damaged or blocked VDOT pipes, ditches or outfall streams to nearby water bodies.
DAA also claims Route 609 in Onemo near an outfall to the marsh has an elevation of one foot. But anyone with any knowledge of the local geography knows that the marshes there are at least 1 ½ feet to two feet above sea level because high water marks from high tides. It stands to reason that the roads must be somewhat higher — after all, no one would build a road lower than the marsh!
Those two examples are the only affirmations of sea level rise that impacts roads in the DAA study, and neither one withstands scrutiny.
Visual Proof VDOT Road Flooding is Not Sea Level Rise
Citizens of Mathews county have gathered abundant photographic evidence showing the road flooding that occurs due to poor ditch maintenance. The photos below show just three of many documented examples.
These same roads pictured above show no signs of flooding close to the water or lower elevations, and adjacent wooded areas have not died from salt-water contamination. The cause was poor pipe and ditch maintenance, not sea level rise. Indeed, VDOT has corrected one area, is about to take care of a second, and will fix the third in 2017 under a revenue sharing arrangement with the locality.
The end of this story will play out this year. Here’s hoping the Commonwealth Center for Recurrent Flooding Resiliency doesn’t rely on past studies without fact- checking them and recognizes that LiDAR maps are fallible. Bad information can’t fix stormwater management and ditch problems in Virginia.There are currently no comments highlighted.