Non-contact hydrometric systems for headwater catchments

Delivery of water from small, rapidly responding catchments, may play a critical role in determining the magnitude and timing of flood waters reaching communities downstream. These headwater areas may themselves also be predisposed to the occurrence of flooding from intense rainfall. As a result, many of these headwater systems in the UK are undergoing changes in land management with the introduction of natural flood management (NFM) features designed to attenuate flows. Yet established hydrometric networks often fail to adequately sample these catchments, with a lack of information about how they operate under pre-NFM conditions. This may hinder the ability of communities to understand the schemes' effectiveness at a catchment scale, and to quantify their cost/benefit. Here we present a novel, non-contact approach for measuring key hydraulic parameters in open-channels, which is well suited to headwater catchments where installation of fixed infrastructure, and flow gauging at peak flows may be difficult to achieve. Each hydrometric station is equipped with multiple ultrasonic sensors across a monitored reach to provide non-contact river level measurement (and energy gradient). A near-infrared video camera is also installed from which optically visible features of the free-surface are tracked to estimate depth-averaged flow characteristics from the free-surface velocity. These systems are controlled by Raspberry Pi 3 microcomputer's and are able to transfer data using 3G, LAN, WLAN, or satellite internet protocols. Data is processed in real-time with outputs hosted in an online user-interface. Real-time data feeds are publicly available whilst videos provide an assessment of current channel conditions (e.g. evidence of large debris transport, temporary blockages and, geomorphic change), which may be of benefit for first responders.