Hydrodynamic modelling of the tide propagation in a tropical delta: overcoming the challenges of data scarcity

Abstract:

Tropical river deltas are hotspots of human activity, but their vulnerability to flood risks is increasing due to sea level rise and worldwide conversion of mangroves, acting as natural buffers against marine flooding, into human land use. Moreover, extreme sea levels notably driven by climatic fluctuations such as the El Niño-Southern Oscillation, are projected to intensify with global warming. Hydrodynamic models offer a valuable tool in reaching a better understanding on the distribution of extreme sea levels in tropical deltas, but often their development is hampered by data scarcity. We combined state-of-the-art techniques to overcome that challenge by setting up a TELEMAC-2D model for the Guayas delta (Ecuador), a large (±3,000 km²) delta with a complex geometry of branching river channels and mangrove forests. First, we used remote sensing to (1) obtain channel widths, which in turn determine the cell size in a flexible mesh, allowing us to capture both regional and local processes,(2) estimate intertidal flat topographies, and (3) delineate intertidal mangrove forests. Furthermore, we used an along-channel-coordinate interpolation to ensure channel connectivity in channels with scarce bathymetric observations. Finally, to capture the land-sea gradient in the water surface slope, we referenced all bathymetric and tide gauge data to a global geoid. Applying these techniques allows us to build a model which simulates tidal ranges (of 2 to 4 m) with an error ranging between 0.2 and 29 cm (ie 0.2 and 7.8% of the observed tidal range), depending on tide gauge station. In a next stage, our model can be used to test how both El Niño and land use …

Año de publicación:

2021

Keywords:

Fuente:

google