Flash flood hazard in Jammu

Dr Vivak M Arya, Tamanna Sharma Flash flood is the rapid flooding of low-lying places with sudden and huge amount of water. A cloudburst, violent thunderstorm or tropical storm may generate a substantial amount of water which can be converted to flash floods with potential of huge human and economic loss. Flash floods can also happen after the destruction of a man-made dam or a natural ice or debris dam. These abrupt increases in water levels typically occur during or after a period of heavy rain. These are extremely localised events of short duration with a very high peak and usually have less than six hours between the occurrence of the rainfall and peak flood. Intensity of the rainfall, location and distribution of the rainfall, topography and land use, vegetation types and growth/density, soil type, and soil water content all influence how quickly the flash flooding may occur in an area. Flash floods frequently pose a substantial risk due to their sudden occurrence. They are significantly more powerful than riverine floods due to their quickness, and they frequently turn into raging torrents of water that destroy everything in their path. It is widely accepted that the observed global warming and climate change are mostly the result of human intervention with the climate system. The Intergovernmental Panel on Climate Change (IPCC) warns of the possibility of an increase in the frequency and severity of catastrophic weather events like temperature extremes, persistent rain, and windstorms due to the inextricable link between climate change and development. A combination of heavy rain, poor management, failure of the natural drainage system, and an unplanned developmental path without taking into consideration the scientific basis lead to flash floods.It is widely accepted that clearing vegetation without proper rain water harvesting raises the risk of mudslides and precipitation runoff. The problem of flash floods is largely facilitated by encroachments of river beds or khads, unorganized and unscientific construction of houses and colonies and deforestation. Trees play a significant role in the prevention of uncontrolled runoff by offering large canopy of vegetation and roots holding the soil. Trees and vegetation also decreases the impact of high rainfall water thereby decreasing the soil erosion. The physical blockage of the trees causes hydrodynamic drag, which slows water speed, while their roots help to keep soil in place. Urbanization is unabatedly growing at an alarming rate in Jammu division which is essential as per human requirement and increase in population. But every new colony, street or single household unit should take into consideration all measures of urban scientific management before the construction of concrete structures. Sudden urban growth, unscientific land use and damaging consequences of climate change are adding to the frequency of flash floods especially in rainy sesaons. This is what we have witnessed recently in Surankote town of Poonch district and Udheywala in Jammu districts causing damage to houses, vehicles, shops and other commercial properties. Flash floods are mainly exacerbated by the blockage, diversion and encroachment of the street nallahs and khads in the town and city and poses a serious threat to human life and property. Nallahas and Khads are like peripheral vascular system taking water out from cities and towns. Land encroachment on nallahas and khads, garbage dumping and plastic-clogged drainage systems are the main causes of floods in most of the cities which can lead to devastating consequences. Due to the abundance of hard concrete surfaces, urban areas are more likely to experience flash flooding during rainy seasons. Impacts of flash floods are many which include loss of precious human life, property loss, loss of income, decline in purchasing and production power, mass migration, psychological repercussions on individuals. In locations where flooding seems to be a regular problem, the effects of floods on land value may cause a fall in real estate value. Flash flood runoff carries pollutants and garbage into rivers and seas. Destruction of roads, buildings, bridges and communication services is another serious effect. Flash floods can cause rapid soil erosion up to the tune of 70 tonnes/ha in hilly areas. Numerous people have lost their homes and livelihood due to floods. Pir Panjal and hilly areas of Jammu province reported numerous incidents of precious human and property loss due to flash floods, landslides and collapsing of kuchha houses. However, flash floods can be controlled by adopting management strategies viz: Pakka bunds on embankment, use of wire crates, use of kachha pakka bunds, planting of trees on sides of khads and seasonal nallahs and making of water outlet valves for sudden or flash floods. Proper land use planning as per the scientific guidelines should be taken into consideration wherever colonies are to be made. NOC for commercial as well as personal construction should be made stringent and it should not be a mere formal exercise rather officers from local municipality, corporation and chief town planner or his subordinate officer should personally visit site to make sure that the buildings are made as per the norms laid down by the government agencies. The creation of effective urban drainage systems and the cleaning and unblocking of drains before the rainy season are must to decrease the intensity of flash floods. Solutions such as riparian zone management, reforestation along river channels should be practiced in letter and spirit that will results in rainwater retention and decreased river discharge. Enhancing flood warning and emergency management systems with the provision of alarm and hooters on rivers, big nallahas and khads should be made mandatory for protecting the precious human lives. Use of audiovisual aids and announcements from local radios, FMs and religious places can be quite helpful for early warning system. Now a day’s mobiles are almost used by everyone, we can use this smart tool by sending warning and flash alert messages to those who are navigating in to riverbeds for their livelihood like tipper drivers, helpers and labourers involved in legal mining business. Water harvesting should be made compulsory for every urban and semi- urban households as this will help in collection of rainwater and reduce the runoff rate. Participatory methods boost the effectiveness of managing flash floods by making local populations aware of the risks. Various platforms like TV talk shows, debates in schools and colleges, general discussions etc. should be used to make the common people aware about the current scenario. Conclusions: Flash floods, which combine extreme speed with a flood’s destructive strength are the most dangerous kinds of floods. Flash floods are a serious threat in densely populated areas. They normally happen during the monsoon season. Flash flooding results in devastating effects on the business, environment, and people. Flash floods are difficult to control using conventional flood management techniques. The various measures implemented by Government can’t be successful without the efforts of common people. We all need to do little on our part to make our environment and surroundings a safer place for everyone. The optimal combination of measures from the Government as well as from society are needed to reduce the impact of flash floods. (The authors are working in the field of NRM & climate change at SKUAST-J)