An absorbing dynamometer acts as a load that is driven by the prime mover that is under test (e.g. Pelton wheel). The dynamometer must be able to operate at any speed and load to any level of torque that the test requires.
While some causes are obvious, such as hurricanes and snow melt, many are not. Heavy Rains: Cresting rivers, backed-up storm drains, or saturated ground can cause significant floods. Heavy rains can contribute to flash floods, which are the number one weather-related killer in the United States. A flash flood is a rapid flooding of low-lying areas in less than six hours. Heavy rains also increase the chance of mudflows, rivers of liquid, and flowing mud.
One cause of floods can be forecast months in advance--snow. Sometimes the ground is too hard or too wet to soak up water. The only place the rain can go is downstream. Usually rainfall of more than one inch in one hour is needed to cause a flash flood. Sometimes a place can get hit by a flash flood even if it's sunny because it might be raining on higher ground somewhere. The floods in Poland this summer weren't flash floods. They were caused by heavy rainfall but the rain was spread out over days. So much rain fell that the rivers couldn't handle all the water.