Mathematical modelling of silting in the Kugart river, Kyrgyzstan

The Kugart River, Kyrgyzstan, has been partly channelised in the past decades with the aim of reducing floodingrisk for the villages of the surrounding, fairly densely populated flood plain. The reduction of the channel width was expected to improve the channel conveyance of the high sediment load produced by the river basin. The resulting longitudinal sequence of relatively sharp channel expansions and contractions has, however, triggered rapid siltation rates in the narrower reaches. Such a relatively unexpected dynamics motivated the application of a numerical model to understand the causes of the silting processes. Migrating sediment waves related to channel expansions and contractions are found to be the main driving forces of aggrading and degrading processes. The outcomes of the analysis allow to suggest possible mitigation measures to reduce the high silting rates and disclose the main parameters which govern the process.