Flash flood in Himachal Pradesh
- Flash floods after cloudbursts have been reported from the hill state of Himachal Pradesh.
- A flash flood is a rapid flooding of geomorphic low-lying areas: washes, rivers, dry lakes and basins.
- It may be caused by heavy rain associated with a severe thunderstorm, hurricane, tropical storm, or meltwater from ice or snow flowing over ice sheets or snowfields.
Causes of flash flood:
- Heavy rainfall and cloud bursts
- Heavy melting of ice and snow,
- Changes in river systems and large catchment areas,
- Sediment deposition/Silting of river beds,
- The collapse of dams,
- Transgression of sea at the occasion of tropical cyclone
- Tsunami in coastal areas and landslides in course of rivers
- Deforestation
- Unscientific use of land utilization and bad farming practices
- Increased Urbanisation, reduced the ability of the land to absorb rainfall
Impacts:
- Loss of lives and loss of property
- Loss of crops
- Loss of fertile soil cover.
- leads to changes in habitats, destruction of habitats
- loss of animals due to drowning.
- Disruption of the lines of rail, road communication, and essential services
- Spread of water-borne and infectious diseases like cholera, gastro-enteritis, etc. immediately after floods.
- Positive consequences:
- Every year floods to deposit fertile silt over agricultural fields which are good for the crops.
- It also recharges the groundwater table.
cloudburst :
- It is defined as a sudden, very heavy rainfall, which lasts only for a short period of time and is extremely local in nature.
- Rain over 100mm per hour is categorised as a cloudburst.
- Cloudbursts usually occur in connection with a thunderstorm.
- During these thunderstorms, a large amount of water may accumulate at high levels and, if the upward currents are weakened, the accumulated water comes down at one time, causing flash floods.
Reason of cloud burst:
- The air currents rushing upwards in a rainstorm hold up a large amount of water.
- If these currents suddenly cease, the entire amount of water descends on to a small area with catastrophic force all of a sudden and causes mass destruction.
- This is due to a rapid condensation of the clouds.
- They occur most often in desert and mountainous regions, and in interior regions of continental landmasses.