Flood Insurance is not Water Backup Insurance that you can add to your homeowners package. In Fact, it is only offerred through The National Flood Insurance Program
Normally, the rates are based on the flood ocurrence in an area over the last 100 years. The more floods the area has had during this time period, the higher the risk. The higher the risk, the higher the premium. Here is the Risk Calculator
This is no ordinary year. Many areas have had record snow and rain. If you live near the mountains, that water has to go somewhere.
Call your homeowners insurance agent and tell him you want a policy from the National Flood Insurance Program. If he cant help you, contact an agent that can.
I deal in probabilities. Not absolutes. If you are in California, Utah or any other state with a heavy snowpack, get flood insurance.