The excess water flows from the reservoir through the spillway and back to the downstream river or drainage channel. A spillway must be large enough to handle the water from a major flood. Dams can create serious safety hazards. If a dam collapses, it can cause enormous property damage, injury, and sometimes death. A dam can collapse because of faulty construction or an earthquake.
Erosion can also lead to a dam's collapse.
A dam can be eroded from the inside by water leaking into the embankment, the foundation, or structures attached to the dam. If the spillway is too small, water may flow over the top of the dam and cause erosion. History Dams have influenced civilization for thousands of years, especially cultures that depended on irrigation. The ancient Romans built dams of cut stone throughout the Roman Empire. Some of these dams are still in use today.