Investigating the impact of fallen tree trunks on the river flow path on the characteristics of the Hyporheic area using Comsol software (Case study of Garmabdasht River, Gorgan)

Document Type : Original Article

Authors

1 Ph.D. student of hydraulic structures, Sari Agricultural sciences and Natural Resources University and expert in irrigation and drainage networks of Golestan Regional Water Company

2 ,Associate Professor, Department of Water Engineering, Faculty of Agricultural Engineering, Sari Agricultural Sciences and Natural resources University, Sari, Iran

3 Associate Professor, Department of Water Engineering, Faculty of Agricultural Engineering Sari Agricultural Sciences and Natural Resources University, Sari, Iran

4 Associate Prof., Dept. of Water Engineering, Gorgan University of Agricultural Sciences and Natural Resources., Gorgan., Iran

Abstract

In rivers, the combination of surface flow and subsurface flow generates Hyporheic flow in the porous environment beneath and surrounding the river. To quantify exchange rate between surface and subsurface water, it is crucial to estimate hydraulic conductivity between the two sources of water. In this study, hydraulic slope and hydraulic conductivity of river bottom sediments were estimated using a mini-piezometer and manometer. Physical experiments were conducted to investigate the impact of natural obstacles on the river path, specifically tree trunks at varying heights (30-60-90 cm), in the year 2022 and Tuskestan River in Gorgan. Piezometers were placed upstream and downstream of the tree trunks, and the resulting hydraulic head difference was assessed through numerical modeling using COMSOL software to simulate hyporheic flow. The study found a 91% correlation between piezometer observation data and numerical solution results, which facilitated further investigation into computational exchange flows. Based on this, the computational exchange flows from the numerical model were also investigated. The results indicated that the highest amount of equilibrium flow occurs in the case where the height of the tree trunk is 30 cm (the exchange flow is 3.96 times without the tree trunk).

Keywords