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

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.

A morphological investigation of marine transgression in estuaries

“…This is distinct from low‐lying alluvial systems for which the length is determined by the morphodynamics of the system (Seminara et al ., 2010); and the discharge and valley slope at the tidal limit define a river channel, and the estuary must converge to this section. The need to introduce a means of estimating the width of the system arises because the defining equations do not allow the width or cross‐sectional area to be determined based on the governing equations alone (Davies & Woodroffe, 2010) and several researchers have resolved this issue by using the river dimensions as an additional control (Leuven et al ., 2018; Savenije, 2015; Townend, 2012). These two components, valley and estuary, are linked by sediment deposition.…”

Editorial for the Special Issue “Remote Sensing of Flow Velocity, Channel Bathymetry, and River Discharge”

“…The papers published in this special issue span a wide range of topics, from specific measurement techniques [3] and rigorous evaluation of a particular sensor [4] to studies illustrating the diversity of ways in which fluvial remote sensing can be applied [5,6]. We identified five emergent themes from the work presented in this special issue and allocated each of the published papers to one or more of these themes, as some articles addressed more than one of the following topics:…”

“…A second application-oriented paper in this special issue further illustrates the many ways in which remote sensing can contribute to our understanding of river systems, all the way to their termini in estuaries. Leuven et al [6] focused on intertidal areas where human activities and rising sea levels impact the distribution of depths and thus habitat conditions. Although numerical modeling can provide information on the spatial pattern and duration of inundation, as well as peak flow velocities and salinity, the requirements of these models in terms of both data and computing power can be prohibitive.…”

“…Although numerical modeling can provide information on the spatial pattern and duration of inundation, as well as peak flow velocities and salinity, the requirements of these models in terms of both data and computing power can be prohibitive. As an alternative, Leuven et al [6] presented a Python-based software tool that predicts hydrodynamics, bed elevations, and the distribution of channels and bars at minimal computational expense. These predictions are based on empirical relations derived from natural estuaries and the only inputs required to use the tool are an along-channel width profile and tidal amplitude, both of which can be derived from remotely sensed data.…”

“…Applying remote sensing techniques to characterize flow-related spatial and temporal heterogeneity of key river attributes [5,6] In addition to this special issue focused on discharge and its components, we also want to direct the reader's attention to another special issue on "Remote Sensing of Large Rivers" published in Remote Sensing in 2020. This editorial was inspired by and is modeled after the overview of "Remote Sensing of Large Rivers" presented by Alcantara and Park [13].…”