The number of dams in in New Hampshire most at risk of failing has increased 51% in the past three years, according to an Associated Press analysis. The state saw its numbers of high hazard dams in either poor or unsatisfactory condition go from 37 to 56, according to the analysis released Thursday. All but one of those dams had a poor rating, with only one rated as unsatisfactory. Steve Doyon, the state’s chief dam safety engineer, said most of the dams were state owned. He attributed the increase to structural problems with dams like leakage, sinkholes and deterioration of the concrete. The other problem was that some spillways — which prevent water from overtopping a dam — were found to be unable to handle a historic flood.