James Houle, the program director at the University of New Hampshire’s Stormwater Center, led a presentation about “innovative approaches” to municipal stormwater during a Monday Zoom event hosted by the Martha’s Vineyard Commission.
“I just wanted to talk about what climate change means to stormwater,” Houle said. “Naturally, it’s three things. We have sea level rise, we have storm surge, and we have increased extreme precipitation. Obviously, the only one that really intersects the world of stormwater is changing precipitation trends.”
According to data from the Intergovernmental Panel on Climate Change’s “Synthesis Report” shown by Houle, heavy and extreme precipitation has “very likely” intensified, and become more frequent, because of the rise in global temperatures. Houle presented a map of America that showed blue and white dots to demonstrate the increase or the decrease in precipitation respectively. For example, southern New England is covered by blue dots, while Florida showed barely any precipitation changes, or precipitation going down in the region.
“Given the choice, I would rather deal with too much water, although either side of the coin is not a good scenario. It’s something we need to plan for,” Houle said. He also said many of the increases could be seen gradually climbing starting in 1996, and more places will see “greater and greater” storm events.
The amount of research and projections on this subject is increasing because of expectations about future precipitation. For example, Cornell University’s Northeast Regional Climate Center is updating rain records, while taking into account historical information. Massachusetts is also in the process of updating its “Stormwater Handbook.”
These changes to precipitation projections also changed “land use patterns,” according to Houle. One of these changes is impervious covers, a theoretical model saying the stronger the cover, the more the benefits to the streams decrease. Blocking only 10 percent of runoff is the supposed “magic threshold.”
“What this tells us is that as we change the landscape from a natural force, or a vegetative landscape, into a more urbanized landscape … we see a corresponding degradation of adjacent water quality,” Houle said. The “thousand-pound gorilla in the room” is that the change in land use also affects the environment, sometimes with similar effects as climate change. What helps is to have places be hydrologically efficient. An example is Five Corners in Vineyard Haven and its flooding. Houle said trying to manage the drainage up the street, such as Beach Street and State Road, would help relieve some of the pressure on the lower areas. Houle told the audience he will be taking part in research on solutions to Five Corners flooding.
Houle said other methods of dealing with stormwater, if there is space, include options like porous asphalt, pervious concrete, retention ponds, and other methods.
A number of years ago West Tisbury did an experiment with ‘porous’ concrete on the drive apron in front of the previous town library building. The adjacent parking area was unpaved in those days, and that contributed heavily to the failure of the experiment. Sand and soil quickly tracked onto the porous concrete, clogging the pores, and reducing the permeability to near zero. The mud problem was replaced by standing water. The lesson is that porous concrete and asphalt have to vacuumed periodically to remove the accumulated grit and restore the porosity. In our climate where sand is spread very liberally all winter long vacuuming the surfaces is essential.
Good comment , Richard. it shows that a single solution does not work everywhere.
I think Tisbury is trying to address the problem of sand getting into many things ( like the drains on beach road) by either greatly reducing or eliminating sand in the mixture for treating the roads during snow events.
Kirk — could you give us an update as to how well you think that worked this winter ? I noticed no sand on the snow covered roads this past winter– Did you get any feedback from drivers ?
I also notice less sand on the roadsides this spring– happy happy bicyclist. !
Thanks..
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