It's a give and take. Historically, the danger from flooding actually increased because the floodplains next to the riverside were mostly eliminated. They would

It's a give and take. Historically, the danger from flooding actually increased because the floodplains next to the riverside were mostly eliminated. They would provide flexibility for the river to meander and to expand in times of heavy rain and would have to be restored as part of a dam removal. They also provide biodiversity and help keep the river water clean. Dams are also a hazard when there is a lot of rain because you eventually have to open it or risk failure. As the dam gets older it tends to silt up and its integrity becomes less trustworthy, even less water fits in. This requires necessitating expensive maintenance to remedy. Getting rid of it might be cheaper in the long run.