A novel toolbox for accurate thalweg detection applied to the estimation of salt wedge intrusion length

The river thalweg is the deepest continuous path along the riverbed. Its accurate determination is relevant for various applications, ranging from navigation optimal pathways to along estuary estimates of salt wedge intrusion. This study introduces an innovative, accurate and open source approach to the detection of the thalweg, by leveraging an iterative path-finding algorithm, enriched with a loop-prevention mechanism. The tool has been applied to the bathymetric datasets interpolated onto a triangular mesh of a finite-element model used to numerically solve the river–sea continuum system of two test cases i.e. the Po and the Tiber deltas. The detected thalweg shows a strong agreement with deepest-point observed along cross-sections (correlation , up to 0.996; ). Further improvements were obtained after optimization (reaching MAPE < 1% ). The tool proved to be effective even in data-scarce branches with nearly uniform bathymetry and in presence of meanders, islands and lateral water bodies. A second tool has been developed and applied downstream of the thalweg detection to estimate the salt wedge intrusion length along delta branches by processing the salinity field produced by a river–sea continuum modeling systems. Both tools can support model practitioners and end users in managing modeling datasets and operational decision-support systems, such as drought early-warning applications.