Geotechnical Aspects of Recent Extreme Floods in Pakistan; A Case History

Topographically, Pakistan comprises three major areas; Northern Highland Area, Indus Basin and Baluchistan Plateau. Its elevation varies from Mean sea Level (0 meter) at south to 8619 meters in the North at K-2 Peak. Northern Highland Area, generally sloping southwards includes Himalayan, Karakorum and Hindu-Kush ranges covering approximately an area of 155,831 square kilometers. Indus Basin stretches from foothills of Northern Highland Area to Arabian Sea in south covering approximately an area of 346,259 square kilometers. Baluchistan Plateau in the West and South comprises mountain ranges of Koh-i-Suleman, Kirther, blow-outs of coralline and lacustrine deposits along coastal belt and covers approximately an area of 347,190 square kilometers. Climate of the country varies from tropical to temperate with rain fall variation of as little as 10 inches a year in South to 150 inches a year in the North. Any rainfall surges in the North frequently unleash floods along the Indus Basin. Continuous deforestation and fires in Northern Highland Area, growing housing projects alongside water channels in the backdrop of global warming and climate change has enhanced frequency and severity of floods in Pakistan. The year 2010 witnessed the worst flood in the history of Pakistan. The causal factors of this rare event are attributed to the amalgamation of two weather systems over Hindu-Kush and Karakorum ranges in the North. The resulting outburst in the realm of denuded landforms graduating from North to South brought about the hydrological extremes never seen before. The event was accompanied with landslides along the slopes washing away numerous houses, over-flowing water channels destroying habitats in the flood plains, precious crops, bridges, and endangered barrages and dams. While scars of a little less similar phenomenon in year 1992 due to cloud burst in Kashmir are still visible on the face of Nation, this flood caused 1985 deaths, 2946 injured; 20 million people were left homeless and destroyed 2.2 million hectares of cropped area, while damage to communication infrastructure is estimated in billions of dollars. The study encompasses geotechnical aspects of landform distribution, climatic changes and hydrological responses