Abstract
Abstract. Accurately monitoring river flows can be challenging, particularly under high-flow conditions. In recent years, there has been considerable development of remote sensing techniques for the determination of river flow dynamics. Image velocimetry is one particular approach which has been shown to accurately reconstruct surface velocities under a range of hydro-geomorphic conditions. Building on these advances, a new software package, KLT-IV v1.0, has been designed to offer a user-friendly graphical interface for the determination of river flow velocity and river discharge using videos acquired from a variety of fixed and mobile platforms. Platform movement can be accounted for when ground control points and/or stable features are present or where the platform is equipped with a differential GPS device and inertial measurement unit (IMU) sensor. The application of KLT-IV v1.0 is demonstrated using two case studies at sites in the UK: (i) river Feshie and (ii) river Coquet. At these sites, footage is acquired from unmanned aerial systems (UASs) and fixed cameras. Using a combination of ground control points (GCPs) and differential GPS and IMU data to account for platform movement, image coordinates are converted to real-world distances and displacements. Flow measurements made with a UAS and fixed camera are used to generate a well-defined flow rating curve for the river Feshie. Concurrent measurements made by UAS and fixed camera are shown to deviate by < 4 % under high-flow conditions where maximum velocities exceed 3 m s−1. The acquisition of footage on the river Coquet using a UAS equipped with differential GPS and IMU sensors enabled flow velocities to be precisely reconstructed along a 180 m river reach. In-channel velocities of between 0.2 and 1 m s−1 are produced. Check points indicated that unaccounted-for motion in the UAS platform is in the region of 6 cm. These examples are provided to illustrate the potential for KLT-IV to be used for quantifying flow rates using videos collected from fixed or mobile camera systems.
Highlights
1.1 Challenges in hydrometryObserved flow rates in rivers represent the integration of water basin input, storage, and water transfer processes
Upon analysis of 10 videos acquired from the fixed camera, as well as 4 videos acquired from the unmanned aerial systems (UASs), flows are reconstructed for a river stage ranging from 0.785 to 1.762 m, on both the rising and falling limb of the hydrograph
Analysis of the footage acquired from the UAS and fixed camera enables the generation of a well-defined rating curve relating river stage to flow, with deviations between reconstructed discharge of 4 % and 1 % in the case of a river stage of 1.762 and 1.518 m respectively
Summary
1.1 Challenges in hydrometryObserved flow rates in rivers represent the integration of water basin input, storage, and water transfer processes. Accurate long-term records are essential to understand variability in hydrological processes such as the rainfall-runoff response (Hannah et al, 2011; Borga et al, 2011). Current approaches for the quantification of river flow are generally applied at strategic locations along river networks through the installation of fixed monitoring stations. Many of these stations are reliant on the development of an empirical stage–discharge rating curve, which is often achieved by developing an empirical function between paired measurements of river flow (combining measurements of velocity and cross-section area) and river stage measurements.
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