BEAT Gets State To Update Its Stormwater Calculations

Good news from Berkshire Environmental Action Team:

Our climate is changing. There really isn’t any debate in the scientific community anymore. The scientific community has moved on to solving the problem of what do we do about climate change. One thing we can do is change our preparedness for more intense storms and heavier rainfall. Most of the country has been doing this. Forty-eight states have updated their formulas used to calculate the amount of water that can be expected to flow in streams and rivers during typical and atypical storms. Rhode Island has been working on updating their calculations so that they can become the 49th state. That leaves Massachusetts as the only state not updating its stormwater calculations.

These calculations are used to predict the amount of floodwater a community can expect during an x-year storm (e.g., 50-year storm, 100-year storm, 500-year storm). This can help determine such things as how big a culvert under a road needs to be in order to keep that road from washing out during a storm. Well, Massachusetts has joined the fold, and has started taking steps to become the 50th state to update its stormwater calculations, and if we do say so ourselves, BEAT was the driving force in getting the state to act.

For quite some time BEAT has been asking Massachusetts state agencies to update the state’s 100-year flood calculations. Then in September 2011, the state released its Massachusetts Climate Change Adaptation Report . On page 19 the report states, “By 2050, Boston could experience the current 100-year riverine flood every two to three years on average and, by 2100, the current 100-year riverine flood is expected to occur every one to two years under both the low- and high-emissions scenarios.” Clearly the state recognized that the current 100-year flood, has been occurring much more frequently than its title would suggest. Our climate was changing, but the design of our culverts, bridges, and other infrastructure components were not. When developers came into meetings with plans, they still used the outdated equations for how much rain falls in how many hours to produce the x-year storm – which would result in the x-year flood.

In September, BEAT contacted the United States Geological Survey to say that BEAT was frustrated by planners’ and engineers’ use of the x-year storm as a design standard, when the x-year storm is now occurring much more frequently. We would like to see a new set of values used to determine the size of each of the x-year storms based on either the most recent historical records, or perhaps even better, based on predicted rainfall for the next 100 years…

On January 17th, 2012, Phil Zarriello from USGS emailed to say thank you, BEAT’s efforts appeared to be making a difference…

…Massachusetts has joined with other New England states to analyze precipitation records to update standards.

All of this should go a long way in reducing future damage from severe storms.

See also:

“UMass geologists: New England may be facing higher risk of flooding as groundwater levels rise”

Christian Science Monitor: “How to plan better for New England floods”
The Kohl Construction condominium proposal for North Street relies heavily on stormwater assumptions (see PDF) that may be outdated. Kohl assumes that a typical 24-hour 2-year rainfall is 2.95″, a 10-year rainfall is 4.45″, and a 100-year rainfall is 6.50″. Maybe this is still true, but when you build as close to wetlands as Kohl proposes to, there’s little margin for error.

Heat and Rain Increasing in Massachusetts: Implications for Infill and the Proposed Landfill Expansion
Over the past century, according to data from the National Oceanic and Atmospheric Administration, average annual rainfall in the commonwealth has increased from about 36 inches to nearly 50 – a jump of over 33 percent…