Floods in himachal pradesh
c) Floods:Floods are another form of natural disaster the State experiences every year. South west Monsoonal rainfall during the months of June to August is the dominant cause for triggering floods when rainfall happens to be in excess i.e. 125% or more than the normal. Fig 2.5 shows the percentage frequency of excessive rainfall and successive years of excessive rainfall during the period from 1951 to 1999. During this period the Chamba district in the north western part of the state had received highest amount of rainfall expressed as percentage of the normal with more numbers of successive years of excessive rainfall. Table 2.11 gives the district wise excessive rainfall years and highest annual rainfall expressed as percentage of normal and Table 2.12 gives successive years of excessive rainfall. Fig 2.6 is the map of flood prone areas as prepared by Dr D.D Sharma of H.P University Shimla.
Flash Flood:Flash flood is the most frequent and damaging floods that occur with little or no warning causing immense loss to life and property. Flash Floods usually takes place when rapidly rising and flowing surge of water reaching full peak within few minutes is generated as a result of excess rainfall or failure of impoundment. The major causes that are responsible for floods and flash floods in the state of Himachal Pradesh are Cloudburst in upper catchments of the river. Excessive rainfall in the catchments. Melting and Bursting of glaciers due to global warming. Sudden breach or failure of manmade or natural barriers. Change of river course. Landslides triggered due to slope failure or tectonic movements leading to LDOF phenomena.
Over 40 incidents of flash flood and cloudbursts occurred in Himachal Pradesh in the last 12 years and over 35 were feared dead. In August 1994, the Manimahesh cloudburst and flash flood washed away almost the entire length of Chamba-Bharmour road (62 km), over 50 people feared dead, and 2000 injured. The estimated loss was over 450 crore of Rupees. 1997 again saw a heavy flash flood in Maglad in Rampur tehsil of Shimla district. Some of the major flash floods reported in the State are as follows:Glacial Lake Outburst Floods:This phenomenon constituting a sudden discharge of a huge volume of water from such glacial lakes is known as Glacial Lake Outburst Floods (GLOFs). The frequency of such events is increasing in the HKH region since the second half of the 20th century (UNEP, 2003) due to the combined effects of climate change and deforestation. Satellite observation of the mountain top lakes in the region have revealed a steady increase in the size and volume of many of these glacial lakes at high altitudes, enhancing the possibility of a devastating outburst flood affecting sizeable populations and damaging precious socio-economic infrastructure and development assets in the Himalayan belt. Over the years, countries in the region have built many high-value economic and infrastructure assets and the emerging threat from GLOFs has serious implications for their future development pathway.
f) Avalanches:Snow avalanches are the sudden slide of large mass of snow down a mountain. There are several factors, which can affect the occurrence of avalanche, including local weather, slope, atmospheric temperature, vegetation; terrain and general snow pack conditions. Different combinations of these factors can create low, moderate and extreme weather conditions. Most avalanches are very dangerous and cause huge loss of life and property. The temperature variation and wind speed are directly proportional to avalanches. As per the Snow & Avalanches study established on an average 30 persons are killed every year due to this disaster in the Himalaya.
Areas normally prone to Avalanches include Region above 3500m elevation Slopes with inclination 30-45° Convex slopes. Slopes covered with grasses.
Higher reaches of Himachal Mountains receives considerable precipitation in the form of snowfall. The north western sector particularly receives maximum snowfall. In winter season the snowfall varies from 2 to 130cm in pre monsoon season, from 1-42cm and in post monsoon from 2 to 39cm. Annual amount of snowfall varies from 25 to 204cm and number of snowfall days from 6 to 77. Avalanches are common phenomena in the district of Kinnaur, Chamba&Kullu. In the past the only place where avalanches have caused destruction in Kangra District is the Bara Banghal area situated at an elevation of
188500feet above the sea level. The village which was located at the base of steep slopes and on the banks of Ravi River was destroyed many times by the avalanches in the past.
Flash Flood:Flash flood is the most frequent and damaging floods that occur with little or no warning causing immense loss to life and property. Flash Floods usually takes place when rapidly rising and flowing surge of water reaching full peak within few minutes is generated as a result of excess rainfall or failure of impoundment. The major causes that are responsible for floods and flash floods in the state of Himachal Pradesh are Cloudburst in upper catchments of the river. Excessive rainfall in the catchments. Melting and Bursting of glaciers due to global warming. Sudden breach or failure of manmade or natural barriers. Change of river course. Landslides triggered due to slope failure or tectonic movements leading to LDOF phenomena.
Over 40 incidents of flash flood and cloudbursts occurred in Himachal Pradesh in the last 12 years and over 35 were feared dead. In August 1994, the Manimahesh cloudburst and flash flood washed away almost the entire length of Chamba-Bharmour road (62 km), over 50 people feared dead, and 2000 injured. The estimated loss was over 450 crore of Rupees. 1997 again saw a heavy flash flood in Maglad in Rampur tehsil of Shimla district. Some of the major flash floods reported in the State are as follows:Glacial Lake Outburst Floods:This phenomenon constituting a sudden discharge of a huge volume of water from such glacial lakes is known as Glacial Lake Outburst Floods (GLOFs). The frequency of such events is increasing in the HKH region since the second half of the 20th century (UNEP, 2003) due to the combined effects of climate change and deforestation. Satellite observation of the mountain top lakes in the region have revealed a steady increase in the size and volume of many of these glacial lakes at high altitudes, enhancing the possibility of a devastating outburst flood affecting sizeable populations and damaging precious socio-economic infrastructure and development assets in the Himalayan belt. Over the years, countries in the region have built many high-value economic and infrastructure assets and the emerging threat from GLOFs has serious implications for their future development pathway.
f) Avalanches:Snow avalanches are the sudden slide of large mass of snow down a mountain. There are several factors, which can affect the occurrence of avalanche, including local weather, slope, atmospheric temperature, vegetation; terrain and general snow pack conditions. Different combinations of these factors can create low, moderate and extreme weather conditions. Most avalanches are very dangerous and cause huge loss of life and property. The temperature variation and wind speed are directly proportional to avalanches. As per the Snow & Avalanches study established on an average 30 persons are killed every year due to this disaster in the Himalaya.
Areas normally prone to Avalanches include Region above 3500m elevation Slopes with inclination 30-45° Convex slopes. Slopes covered with grasses.
Higher reaches of Himachal Mountains receives considerable precipitation in the form of snowfall. The north western sector particularly receives maximum snowfall. In winter season the snowfall varies from 2 to 130cm in pre monsoon season, from 1-42cm and in post monsoon from 2 to 39cm. Annual amount of snowfall varies from 25 to 204cm and number of snowfall days from 6 to 77. Avalanches are common phenomena in the district of Kinnaur, Chamba&Kullu. In the past the only place where avalanches have caused destruction in Kangra District is the Bara Banghal area situated at an elevation of
188500feet above the sea level. The village which was located at the base of steep slopes and on the banks of Ravi River was destroyed many times by the avalanches in the past.
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