Beaver dam break - NH

One of 3 beaver dams upstream from my home broke rushing 3 ft of water in my lower level of my home. The landowner who currently has the property for sale denies any responsibility. He, the town and the state know theyre there and 2 previous homeowners also flooded from the same property. The town has offered no resolution/protection, the state is conducting a culvert analysis but says they won't put a bigger culvert in to accomadate a beaver dam break just the normal flow of water. The DES says they do not monitor beaver dams only manmade ones. The town previous wrote to the landowner on behalf of the previous residents saying they were responsible for damages downstream and have yet to offer such a letter on our behalf.I got this info thru public records. Everyone is turning their heads. I recently discovered thru meeting minutes of the selectman that $ from the landowner was given to the town and that the town is interested in buying the land for conservation land and federal grant $! I am stuck between a rock and a hard place. This town doesn't particiapate yet, in the Nat'l Flood Insurance Program and I'm not in a flood zone according to FEMA. Even if I had insurance; it has to be 2 acres or more to be defined as a flood in NH. My lot is 1 1/2 acres. I can't even protect myself and am currently in estimated losses of 50K.Plus, I couldn't sell my house if I wanted to because of the flood which would have to be disclosed. It has lowered my property value I believe. Can anyone help or find me a referral that will take it on contingency?
Please help; thank you. Donna