New Mat-Su flood mapping system more accurate

After 2012 floods in the Matanuska-Susitna Borough required disaster relief, many area homeowners living in the flood plain were required to get expensive flood insurance. Now, a new mapping system will allow about a thousand homeowners to consider dropping their flood insurance bills.

Listen Now

According to Matanuska-Susitna Borough development services manager Alex Strawn, a recent mapping project has enabled the borough to reduce or change the outlines of the flood plain. And this comes as good news to some homeowners.

“The importance is that our previous maps were incorrectly drawn because we had poor data,” Strawn said. “It was back in 1985 when we drew them, and we didn’t have near as sophisticated of topographical data, or near as accurate. So now that we have high, accurate topography data, we can get accurate flood maps.”

Strawn said earlier FEMA flood insurance rate maps were based on old, incorrect data. Because of that, Strawn said, the Borough has a lot of people in the flood zone who have not been there in the first place.

In 2011, the Borough got a new LIDAR mapping system, which uses lasers from airplanes to penetrate the canopy of the trees to get a better picture of what is on the ground. The very next year, floods hit the Borough.

“And, it is interesting that a lot of the homes that flooded were not in the flood zone,” Strawn said. “During that time, we also had recognized that our maps were inaccurate. And largely the Butte was a big one, where we realized a lot of homes were in the flood zone that shouldn’t be, because it is all based on a 1971 flood that occurred. So the timing is somewhat coincidental that we had that flood at the same time we were looking at these maps.”

Strawn said the numbers of homes in or out of the flood plane now is based on 2011 data. He said the Borough encourages people to still get flood insurance, whether in or out of the flood plain. But those now outside the flood plain could save between one and two thousand dollars a year in insurance costs. That adds up to a potential total savings of more than $11.7 million over the next fifteen years.

Conversely, about a hundred homes will be moved into the flood plain because of the new data.

Strawn said the new numbers are preliminary and the maps won’t become official until 2018 after a lengthy review process that includes public input. The new mapping does not include the village of Talkeetna.