Comparison of empirical and theoretical remote sensing based bathymetry models in river environments

Knowledge of underwater morphology is an essential component of many hydrological and environmental applications such as flood modelling and lotic habitat mapping. Remote sensing allows modelling of bathymetry at spatial scales that are impossible to achieve with traditional methods. However, the use of passive remote sensing for modelling water depth in fluvial environments remains a challenge. Different methods of computing bathymetry models based on remotely sensed imagery combined with ground measurements for calibration were investigated in order to produce a digital bathymetry model of a reach of the river Tana in Lapland. An empirical deep water correction model was evaluated together with theoretical hydraulically assisted bathymetry (HAB) models. The empirical model produced good results, correlating to known depths at 0.98 (R-2 = 0.96) with a mean error of +/- 12.0 cm. It was demonstrated that usable levels of accuracy can be achieved with data that had previously been considered unsuitable for bathymetry modelling. Some issues related to channel substrate were addressed. The models based on hydraulic theory were tested for the first time outside the area they were developed in. Both models were found to be rather sensitive to certain assumptions, such as the channel friction parameter. The HAB models are able to produce relative depth estimates that can under certain conditions approach actual depths at accuracies similar to the empirical model. Extensive accuracy assessment was performed in order to evaluate the vertical as well as the spatial accuracy of the three models. Copyright (C) 2010 John Wiley & Sons, Ltd.