ReliefWeb

Introduction

Flash floods are one of the most common forms of natural disaster in the Hindu Kush-Himalayan (HKH) region. They consist of sudden and very strong surges of water (usually along a riverbed or gully) and can carry rocks, soil, and other debris. The physical environment of the HKH is conducive to flash floods since these are the youngest mountains on earth and are still tectonically active. Since this area is undergoing uplift, it is characterised by steep slopes and a high rate of surface erosion. In addition to the geological conditions, intense seasonal precipitation in the central and eastern Himalayas (particularly during the summer monsoon season) and in the western Himalayas and the Hindu Kush (particularly during winter precipitation) triggers various types of natural hazards. Floods are one of the most common forms of natural disaster in this region. Intense monsoon rainfall or cloudbursts can cause devastating flash floods in the middle mountains (500–3,500 masl), and rapid melting of snow accumulated during winter is the main cause of flash floods in the Hindu Kush and western Himalayas. Furthermore, the region is experiencing widespread deglaciation, likely due to climate change, which has caused the formation and rapid growth of many glacial lakes. These lakes can burst their boundaries as a result of internal instabilities or external triggers in a process known as a glacial lake outburst flood (GLOF), which can cause immense flooding downstream. Landslides due to intense rainfall, in combination with geological instabilities and earthquakes, can cause the ephemeral damming of rivers. The outbreak of lakes created by such damming is another type of flash flood common in the region.

Hundreds of lives and billions of dollars worth of property and high-cost infrastructure are lost and much scarce agricultural land is destroyed every year in the region owing to landslides, debris flows, and floods. In the last decade of the twentieth century, floods killed about 100,000 persons and overall affected about 1.4 billion people worldwide; moreover, there is every indication that the number of events (and deaths) is increasing (Jonkman 2005). Statistics show that the number of people killed per event is significantly higher in Asia than elsewhere, and that not only are flash floods responsible for the greatest number of deaths among all water-induced disasters (Jonkman 2005), but in addition mortality rates for flash flood events are significantly higher than for riverine floods.

Despite the destructive nature and immense impact they have on the socioeconomy of the region, flash floods have not received adequate attention and the HKH regional capacity to manage this risk is low. This lack of capacity can be attributed to poor understanding of the processes and a lack of knowledge on what measures can be used. This manual was developed to address this need and to help develop regional capacity to manage the risk of flash floods. It contains a training curriculum and the resource materials needed to deliver a basic training in flash flood risk management. The manual has been prepared to help different stakeholders (government staff, non-governmental organisations and other civil society groups, lawyers, academics, and media people) understand the basics of flash floods and the full range of flood and risk management measures for an integrated approach to flash floods, including the importance of community participation, legal and institutional aspects, the latest social hazard mapping techniques, and an introduction to the various modelling tools. The overall objective of the training is to enable participants to effectively help communities and nations to be better prepared for flash floods using the implements that are available. The aim is to develop a pool of people who are able to serve as knowledge multipliers in the region.

In using the manual, it must be remembered that training needs are subject to the specific context in which the training is being conducted. Since national policies and legislation can and do differ among countries, the trainer should try to place the training in the context of the particular situation at hand, including countryspecific policies and legal provisions.