Publication Details
Abstract
Reservoir banks, slopes and the entrances of sheltered bays undergo progressive deformation driven by wind-induced waves and the alongshore currents they generate, threatening the safety, navigability and effective storage of water-supply facilities. This study develops and validates a hydraulic method for predicting wave-induced longshore currents, bank reformation and bay-entrance siltation in unsteady-flow mountain reservoirs, using the Hisorak Reservoir on the Aksu (Akdarya) River (Kashqadarya Province, Uzbekistan) as a case study. The mean longshore current velocity is obtained from a water-mass continuity model of the surf zone that expresses the velocity through the wave celerity and the wave-approach angle, requiring a single surf measurement rather than simultaneous deep-water observations. A longshore sediment-transport relation and a one-line entrance-width model close the scheme, and a shift of the wave breaking point by the current is incorporated to correct the approach angle at oblique incidence. The model predicts that both the maximum alongshore velocity and the maximum entrance siltation occur when the wind acts at about 45° to the shoreline, in agreement with independent field evidence. Validation against nearshore current measurements yields a mean deviation of 11.6 %, and the method reproduces the multi-year narrowing of a bay entrance under repeated clearance. A transverse sediment-retaining structure, dimensioned with the method, reduces the predicted entrance siltation by about two-thirds, extending the clearance interval several-fold. The approach provides a transparent, field-economical basis for forecasting deformation and dimensioning bank protection at arid-zone mountain reservoirs.