Real‐time monitoring and estimation of the discharge of flash floods in a steep mountain catchment

Abstract

Synchronously and accurately estimating the flood discharges and dynamic changes in the fluid density is essential for hydraulic analysis and forecasting of flash floods, as well as for risk assessment. However, such information is rare for steep mountain catchments, especially in regions that are hotspots for earthquakes. Therefore, six hydrological monitoring sites were established in the main stream and tributaries of the 78.3-km 2 Longxi River catchment, an affected region of the Wenchuan earthquake region in China. Direct real-time monitoring equipment was installed to measure the flow depths, velocities, and fluid total pressures of the flood hydrographs. On the basis of field measurements, real-time mean cross-sectional velocities during the flood hydrographs could be derived from easily obtainable parameters: crosssectional maximum velocities and the calibrated dimensionless parameter K h . Realtime discharges were determined on the basis of a noncontact method to establish the effective rating curves of this mountainous stream, ranging from 1.46 to 386.34 m 3 /s with the root mean square errors of ≤10.22 m 3 /s. Compared with the traditional point-velocity method and empirical Manning's formula, the proposed noncontact method was reliable and safe for monitoring whole flood hydrographs. Additionally, the real-time fluid density during the flood hydrographs was calculated on the basis of the direct monitoring parameters for fluid total pressures and water depths. During the flood hydrograph, transient flow behaviour with higher fluid density generally occurred downstream during the flood peak periods when the flow was in the supercritical flow regime. The observed behaviour greatly increased the threat of damage to infrastructure and human life near the river. Thus, it is important to accurately estimate flood discharge and identify for fluid densities so that people at risk from an impending flash flood are given reliable, advanced warning. K E Y W O R D S discharge estimation, flash floods, flow regime, fluid density, real-time monitoring, steep mountain catchment

Reconstruction and Characterisation of Past and the Most Recent Slope Failure Events at the 2021 Rock-Ice Avalanche Site in Chamoli, Indian Himalaya

“…This flash flood took nearly 27 min to cover the ~6 km of the distance between Raini village and Tapovan town (Figure 13), clocking a disastrous velocity of ~4 m/s. This velocity is comparable to those of several reported flash floods in mountain catchments and is capable of carrying a significant amount of debris and sediment to a large distance, destroying any obstructions in the path [77,78]. The large debris and sedimentation spread along the river channel after SF2 is visible on the 10 February 2021 Sentinel-2 image of Figure 14d.…”

Assessment of flash flood risk based on improved analytic hierarchy process method and integrated maximum likelihood clustering algorithm

“…Finally, numerous studies focus on flash flood risk in spatial dimension rather than temporal. Thus, determining how to effectively integrate real-time information to establish a dynamic flash flood risk assessment model in the future is currently a hot issue (Adams et al, 2019, Shirisha et al, 2019, Zhang et al, 2019a, Zhang et al, 2019b. There is no doubt that flash flood assessment will be strengthened by collaboration with other disciplines, such as radar technology and remote sensing.…”

An Agent-Based Approach to Integrate Human Dynamics Into Disaster Risk Management

“…Afterward, due to post-earthquake fractured rock and loose soil on steep slopes, Longchi repeatedly suffered mass movement processes (Zhang et al, 2019). The debris flow that occurred on August 13 th , 2010 (the 813 debris flow) was one of the most destructive debris flows.…”