Medeu Dam

Much of downtown Almaty is built on the alluvial fan of the Malaya Almatinka River, at the point where the river leaves the steep and narrow Medeu Valley for the wider plain. The river valley, steeply descending to the city from the Trans-Ili Alatau mountains, is highly susceptible to the formation of debris flows and/or mudflows. During the 20th century, five catastrophic debris/mudflows happened in the valleys of Malaya Almatinka, or its sister river (further west), Bolshaya Almatinka. The most severe of them was the catastrophic mudflow of 1921 in the Malaya Almatinka valley, triggered by heavy rainfall. It killed 500 people out of Almaty's 45,000 population at the time, and destroyed much of the city. The total volume of that flow is thought to have been 10 million cubic meters (including some 3 million cubic meters of hard material, i.e. rock), coming down to the city at the discharge rate of 900 cubic meters per second. It is estimated that if a repetition of the 1921 mudflow were to strike the city in the early 21st century, the damage would be on the order of US $100 million.

To prevent mudflows from reaching the city, a number of facilities have been built upstream of the city on both the Bolshaya (Greater) and Malaya (Lesser) Almatinka Rivers.^[1]