Application of satellite altimetry in understanding river–wetland flow interactions of Kosi river

Journal of earth system science

Chembolu V^1¹  Dubey A K^2² 

[1]Indian Institute of Technology Guwahati, Kamrup District, Guwahati 781 039, India.^1

[2]Space Applications Centre (ISRO), Jodhpur Tekra, Ahmedabad 380 015, India.^2

关键词: Flood-plain wetland;    river modelling;    satellite altimetry;    HEC-RAS model;    unsteady flow analysis;   

DOI  :  

学科分类：天文学(综合)

来源: Indian Academy of Sciences

【 摘 要 】

Flood-plain wetlands are the seasonal water bodies formed along a river. These wetlands become active during the monsoon season, which frequently grow in size with seasonal floods and eventually dry up during the non-monsoon season. The flow interaction between flood-plain wetlands and the river sometimes vary over a very short period in response to rapid rise in the river water level due to high precipitation in its upstream catchment. Understanding the complex flow interactions between the river and its associated flood-plain wetlands with field-based measurements of wetland hydrologic characteristics is always a challenging task. To overcome these challenges, an attempt has been made to utilise Topex/Poseidon satellite altimetry-derived water levels into a hydrodynamic model (HEC-RAS) to study river and wetland flow interactions in the lower reach of the Kosi river in India. The satellite altimetry-derived water levels and Landsat satellite images on the Kosi wetlands are used to develop volume-elevation relation. HEC-RAS is setup over the study area and calibrated for different values of manning’s roughness coefficient (n) for the river bank and the main channel of the river for the period of 1993–1996. Unsteady flow simulations are carried out for different monsoon seasons to simulate daily river flow interaction (inflow/outflow) between river and wetlands. Statistical analysis is performed between the altimetry-derived and the model-simulated water levels. It is found that simulated water levels are in good agreement ($R^{2}$=0.87, root mean square error of 0.84 m and Nash–Sutcliffe efficiency coefficient of 0.85) with altimetry-derived water levels. The analysis of simulations indicates that interactions between the wetland and the river are bidirectional with most of the flow coming out from the river during the month of August and leaving out from the wetlands during the month of September. The wetlands respond in three different ways, i.e., (i) gaining stage, (ii) wetland and river in equilibrium and (iii) loosing stage, which is reflected on water levels of the river and wetland. This study demonstrates complex interaction processes happening between the Kosi river and its surrounding wetlands.

【 授权许可】

CC BY