Granite Geek: Citizen-Scientist Network Gauging Flood Danger in N.H.

Mar 15, 2016

If you live near a river, chances are you’ve imagined what kind of damage a flood could do to your home. It’s difficult to predict what exactly a hard rainfall could bring. And, as we speak, a volunteer network that stretches beyond New Hampshire’s borders is gathering data on rainfall with the goal of predicting likelihood of flooding or other potential hazards. For more on these efforts, we turn to David Brooks. He’s a reporter for The Concord Monitor and writer at Granite

David, this network is one of those citizen scientist communities. Tell us what this network is and how it’s gathering data.

Sure, it’s got really an awful name. It’s called COCORAHS, which stands for Community Collaborative Rain Hail Snow, and it was started a decade ago, maybe a little more, out in Colorado actually when they had some flooding and they realized they didn’t have enough good precipitation data to help them predict floods.

And, as you say, it’s a citizen science program— there’s actually a bunch of them online now. So it’s a network and a website. People can gather data, daily rainfall data, or snow, and they also can also gather data on hail, and put it into this website every morning, and then they can use it for a variety of reasons actually, including predictions.

I’ve been doing it for three or four years now. You buy a particular gauge from them, they have a specific gauge they want you to use. It’s fairly common. It’s got a funnel system, so it basically aggregates the rainfall, and makes it easier to read. And you go out every morning at about 8:00 and you check it out. And if there’s snow, you go out and you measure the depth, and you also melt it down to find out how much water is in it, because that’s very important to know—there’s a difference in fluffy snow and wet, heavy snow—and you go put it in the website and it’s gathered all over the country.

Okay. So, it’s gathered by citizen scientists, lots of people over varying levels of shall we say competency…

Hey, what are you saying about me?

Sorry, I don’t want to cast dispersions on your abilities, David. But, does that throw some of the data into question if it’s done by different people with differing skill levels?

That’s an excellent point, and that’s one of the issues with these citizen science programs. Of course, we’re amateurs, we’re untrained, and so you have to be a little cautious. In fact, they send out about this saying hey, you know, don’t round off your numbers to make them look nice, things like that, which you would never have to tell to a trained data gatherer. And so you do have to be suspicious or at least cautious about any of the data. The hope is, and generally this works out well with citizen science programs, is you make up for it with volume, frankly.  If there’s no particularly reason for errors to happen on one side or the other, errors typically cancel each other out.  Some of us, you know, go out and we look at the gauge and maybe we think it’s a little higher than it actually is, and some of us go out and think it’s a little lower than it actually is. So, the highs and the lows, if there’s enough of them, over time will cancel each other out. So, you can do an average.

But, definitely this isn’t the same as having, you know… COCORAHS at the moment has about 10,000 active weather stations around the country, they’ve got some in Canada, they’re about to expand to the Bahamas, they’re in Puerto Rico—it’s a really excellent system, and…

You just need more people to counteract the effects of possible flaws in the data.

Exactly. You definitely need more. And what they ideally like is one every square mile, which is never going to happen.


Yeah. There are I think 50 in Merrimack County that I know of, active weather stations that I can see on the site, I looked at it quickly. But, they’d like to have more, and this is the month when they actually do a March Madness drive of their own, trying to get people, if people are interested, to sign up. You can go to their website, it’s And you can look, find out all about it and see.

If you want to participate, all you need to do is buy the right gauges, like $30, $40, something like that. Set it up in the proper spot outside, don’t put it right underneath the porch roof, and set up an account and start measuring.

So, let’s say we did manage to get one of these volunteers in every square mile in New Hampshire, what would the benefit be to people living here?

The benefit, well aside from that it’s fun and that’s it’s nice to have people understanding the weather, but the direct benefit, frankly, for us would be flood management. And drought management, of course.

A specific example is down the Souhegan River, which is a small tributary of the Merrimack down in Hillsborough County. And there’s a couple of automated depth gauges on it that automatically read and it and wirelessly send the numbers out, and you can go on the website and see it. And on one of them, the one that’s near the mouth, it also predicts what the depth is going to be for the next several hours, I forget the exact number, because there is enough data from what’s happening upstream that it can extrapolate. But if you go to the other automated gauge, which is further upstream, it does not guess what’s going to happen over the next few hours, because it does not have eough data. There isn’t enough river flowing, there isn’t another gauge upstream telling them what’s coming, but also there isn’t enough data about what rain has fallen in the watershed and is about to be flowing down into the river.

So, if you had more people who were giving COCORAHS data, that might allow them to do that sort of prediction up further. And if you’re, and this is actually in Milford, and I know half a dozen years ago there was flooding there. And there was this big apartment house right by the river, and the flood came into the basement of the first floor, and there was doubt as to whether it was going to make it there or not.

So, if you’re the person sitting there, trying to decide whether to move all the stuff out of your basement, it would be nice to have a rain gauge that says yes it’s going to go up another foot in the next couple of hours. So, that’s the kind of useful information that this could help provide.