Assessment and Mapping of Mudflow Hazard and Mudflow Risk in the Territory of Almaty

Abstract

The Almaty city, located at the foot of the Zailiyskiy Alatau ridge, is the largest metropolis of Kazakhstan with a population of about 2 million people. The city is located on mudflow fans and has repeatedly been exposed to the destructive effects of mudflows. Mudflow disasters with big material damage and human casualties occurred in 1921, 1950, 1956, 1973 and 1977. Mudflows with material damage were recorded also in 1999, 2006, 2013 and 2019. Maps of mudflow hazard and mudflow risk are necessary for the development of measures for protection against mudflows. In 2018-2019 such maps were compiled by the Institute of Geography for Almaty on the instructions of the Department of Emergency Situations of Almaty. Maps were compiled at a scale of 1:25 000 using GIS technology. To compile the maps, archival data on mudflows from 1900, satellite images, and ground-based observations were used. The mudflow hazard maps show the boundaries of mudflows of various volumes and repeatability. By volume, mudflows are divided into 4 categories: small (<10 thousand m 3 ), medium (10-100 thousand m 3 ), large (100-1000 thousand m 3 ) and very large (> 1 million m 3 ). In terms of repeatability: frequent mudflows (more than 1 time in 50 years), rare (1 time in 50-100 years) and very rare (less than 1 time in 100 years). The volume of mudflow in the field was determined by the maximum size of the boulders, and the