Empirical Assessment Tool for Bathymetry, Flow Velocity and Salinity in Estuaries Based on Tidal Amplitude and Remotely-Sensed Imagery

Jasper Leuven,Wout Van Dijk,Maarten Kleinhans,Sanja Selaković,Steye Verhoeve

doi:10.3390/rs10121915

Abstract

Hydromorphological data for many estuaries worldwide is scarce and usually limited to offshore tidal amplitude and remotely-sensed imagery. In many projects, information about morphology and intertidal area is needed to assess the effects of human interventions and rising sea-level on the natural depth distribution and on changing habitats. Habitat area depends on the spatial pattern of intertidal area, inundation time, peak flow velocities and salinity. While numerical models can reproduce these spatial patterns fairly well, their data need and computational costs are high and for each case a new model must be developed. Here, we present a Python tool that includes a comprehensive set of relations that predicts the hydrodynamics, bed elevation and the patterns of channels and bars in mere seconds. Predictions are based on a combination of empirical relations derived from natural estuaries, including a novel predictor for cross-sectional depth distributions, which is dependent on the along-channel width profile. Flow velocity, an important habitat characteristic, is calculated with a new correlation between depth below high water level and peak tidal flow velocity, which was based on spatial numerical modelling. Salinity is calculated from estuarine geometry and flow conditions. The tool only requires an along-channel width profile and tidal amplitude, making it useful for quick assessments, for example of potential habitat in ecology, when only remotely-sensed imagery is available.

Highlights

Estuaries are characterised by fresh water inflow at the landward boundary and an open connection to the sea
We explore to what degree it is possible to globally estimate estuarine characteristics, such as bed elevation, inundation duration, flow velocity, and salinity based on limited but widely publicly available data: remotely-sensed imagery and tidal range at the estuary mouth
At locations where the estuary is relatively wide, average bed elevations are higher and at locations where the estuary width is close to the ideal width, bed elevations are lower (Equations (4) and (5))

Summary

Introduction

Estuaries are characterised by fresh water inflow at the landward boundary and an open connection to the sea Within these boundaries, tidal flows form dynamic patterns of channels and bars (Figure 1a). Tidal flows form dynamic patterns of channels and bars (Figure 1a) Many of these systems are managed to balance the needs of flood safety, access to harbours and ecological quality. The main channels in large systems such as the Western Scheldt, Elbe and Yangtze are dredged for access to harbours [1], while intertidal area on bars and estuarine shorelines forms valuable ecological habitat [2]. We explore to what degree it is possible to globally estimate estuarine characteristics, such as bed elevation, inundation duration, flow velocity, and salinity based on limited but widely publicly available data: remotely-sensed imagery and tidal range at the estuary mouth. To aid application and further investigation, we make the toolbox available

Methods

Results

Discussion

Conclusion