Flash floods are characterized by rapid flooding of lowlying areas such as rivers, washes, lakes, and depressions. Flash flooding can occur due to heavy rain caused by a hurricane, severe thunderstorm, or tropical storm. Flash floods might also be caused when a natural water or damage dam collapses, or by meltwater from ice or snow flowing over ice sheets or snowfields. Flash floods are distinct from regular flooding because they happen in a shorter time frame than regular floods. Flash floods may also deposit large amounts of sediments on floodplains. These can damage vegetation that isn’t adapted to flooding.
The causes
After a thunderstorm that lasted for 3-5hrs, Flash floods occurred in Northern Mexico. They are common in dry areas where precipitation has just been received. But, flash floods can also occur downstream from the source, sometimes even miles away. Flash floods may also have occurred in areas located near volcanic eruptions. Flash floods can be found in the most remote areas of the United States. Flash flooding can also occur from excessive rainfall caused by tropical storms and hurricanes. When dams are broken, large quantities can be released that could cause destruction of everything.
Hazards
A flash flood is a flood that floods a small ditch. It can also flood barns and cause damage to newly installed drainpipes. Many people underestimate flash flood dangers. Flash floods are most dangerous due to their sudden nature, fast-moving water, and high levels of destruction. Although a vehicle offers little to no protection from being swept away, it can cause people to be more optimistic and less likely not to get swept away in a flash flood. People who get swept away in flash floods are responsible for more than half of all fatalities. Storms that occur in dry areas are very rare, but can still deliver large quantities of water quickly. Second, although storms in arid areas are very rare, they can deliver a large amount of water within a short period of time. Desert roads can cross creek beds and rivers without bridges in certain areas. The driver might see clear weather as an unexpected formation of a river in the area. The canyon becomes flooded, making it difficult to climb the mountain to escape the flood. In southern Utah, on 14/09/2015, there were 20 flash flood fatalities. Seven occurred in Zion National Park. The floodwaters trapped hikers in a canyon.
Flash flood impacts
Flash floods cause severe damage to both the natural and built environment. The consequences of flash floods can be devastating and vary in severity, from damage to buildings and infrastructure to effects on vegetation, lives, and livestock. These effects are especially difficult to quantify in urban areas. Researchers rely on datasets such U.S. National Weather Service storm Data data to correlate the effects of flash floods with physical processes that result in flash flooding. This should increase the reliability in flash flood impact forecasting. Analysis of flash floods across the United States in 2006-2012 shows that there are more deaths and injuries in small rural catchments.
Deaths and Injuries
An assessment of the impact severity of flash floods is being proposed for 2020. It will provide a clear overview of the effects of flash floods through the classification and severity of impacts and the mapping of their spatial extent along the floodplain. Depending on which elements are affected, flood effects are divided into four categories: (i.e., impacts on buildings, (ii., impacts upon man-made mobile items, (iii., impacts onto the natural environment) and (iv., impacts on humans (entrapments of injuries, deaths, etc.). The scale was designed to be used for planning purposes.
