A model of river bank deformations under the simultaneous effect of waves from a hydropower plant and warming

E Debolskaya

doi:10.5194/piahs-364-32-2014

Abstract

Abstract. This paper presents a mathematical model of the river bed deformations in permafrost areas. The deformations are caused by the influence of waves of various origins under an increase of the ambient temperature. The model system consists of an unsteady hydrodynamic module, a thermal module and a bed deformation module. The hydrodynamic module is based on the two-dimensional shallow water equations. The bed deformation module is based on the sediment mass balance conditions. The thermal module is based on the Stefan equation, which defines the "water–ice" boundary movement. We present two applications of the model in which the bed deformation is calculated for the alluvial channels with melting bed under the influences of waves of different duration and intensity. We compared the model predictions with the laboratory data, generally obtaining a good agreement between the two.

Highlights

Arctic regions are very sensitive to global climate change and hydrological systems in these regions are sensitive to the rising temperature
Descriptions of the bed deformations caused by the interaction of mechanical and thermal erosion can be traced in the literature back to 1932
We modelled the formation of thermo-erosional niches and the simultaneous effects of the thermal and mechanical erosion in the laboratory experiments using the following set-up

Summary

INTRODUCTION

Arctic regions are very sensitive to global climate change and hydrological systems in these regions are sensitive to the rising temperature. The laboratory experiments and field observations (Randriamazaoro et al 2007, Dupeyrat et al 2011) showed that thermoerosion plays a significant role in the deformation of the banks composed of permafrost with the inclusion of layers of ice. Sometimes the effect of thermoerosion is greater than that of mechanical erosion. We modelled the formation of thermo-erosional niches and the simultaneous effects of the thermal and mechanical erosion in the laboratory experiments using the following set-up. Two ice plates of equal thickness were embedded in a bank slope at different depths. Under the influence of the flowing water the ice plates melted and formed a cavity in which small streams occurred. Our model describes the process of the lateral bed deformations, and in particular the niching process and allows answering some long standing questions, for instance, what is the role of the icing process in the soil erodibility. The water temperature increased from 7°C to 17°C in 4 h

Mathematical model

Validation of the model and results

Findings

CONCLUSIONS