A stochastic model for simulating long time series of river-mouth discharge and sediment load

Abstract

River dynamics play an important role in the formation of deltaic and fluvial deposits. Typical scenarios comprise long periods of low discharge and sedimentation rates, alternating with flooding events that are characterised by very high erosion and deposition rates. A general problem in reconstructing the scenarios that led to the formation of fluvio-deltaic deposits is the lack of liquid and solid discharge data covering long time intervals. The objective of this study is to present a statistical method that allows the simulation of long time series of fluvial discharge from comparatively short historic records. The method captures temporal variability of river discharge by a stochastic two-parameter model. Model parameters are obtained by statistical analysis of discharge data from modern catchments, based on the hypothesis that long-term average discharge is lognormally distributed. The Discharge Model for Basins (DMB) extends this method to ancient fluvial systems by estimation of climate and catchment parameters. The method is illustrated with data sets of the Terek and Volga Rivers (Russian Federation). The Kura River (Azerbaijan) is presented as a test case in which parameters are estimated from a hydrological database of major European rivers. Tests show that the model is capable of producing estimated monthly and yearly discharge sequences comparable to measured time series, which comprise flooding events. DMB simulations of liquid and solid river-mouth discharge can be used as input for stratigraphic simulation models.