Abstract
Changing climate has raised attention toward weather-driven natural hazards, such as rain-induced flash floods. The flooding model is an efficient tool used in flash flood warning and hazard management. More and more evidence showed significant impacts of sediment on hydrodynamics and flooding hazard of flash flood. But little information is available regarding flooding hazard sensitivity to sediment characteristics, which hampers the inclusion of sediment characteristics into the flash flood warning system and hazard management. This study used a 1D model to simulate flood hazards. After calibrating and validating the hydrodynamic model, we carried out simulations to test the sensitivity of flood hazard to sediment characteristics like inflow point, size distribution, and concentration. Our results showed that sediment from highly erosive slopes affects the flooding hazard more than sediment from watershed. This is particularly true when sediment particles are fine particles with a medium size of 0.06 mm. When medium particle size of sediment increased above 1 mm, most of the sediment particles are deposited in the river and we see little effect on flooding hazard downstream. Sediment concentration significantly influenced the flooding hazard but was less important than sediment inflow point and medium particle size. Our study suggested considering more characteristics than concentration when including sediment particles into the flash flood warning system.
Highlights
Flash floods are one of the most significant natural hazards and cause serious loss of life and economic damage
This study aims at testing sensitivity of flooding hazard to sediment characteristics of inflow, medium particle size, and concentration by using a numerical model
We expected to identify the influential features of sediment to the flash flood hydrodynamics and to incorporate this into the flash flood early warning system
Summary
Flash floods are one of the most significant natural hazards and cause serious loss of life and economic damage. The average annual economic loss due to natural hazards in China has been estimated at $20 billion (Han et al, 2016). Lowland floods are rarely associated with fatalities, except in cases of levee failures in China; in contrast, flash floods often result in loss of life (Chuang et al, 2009; Wang et al, 2017). Good understanding of the flow physics of flash flood is key to efficiently mitigate flash flood hazard as well as the base of series of structural and non-structural measures. Physical experiments and numerical models both provide insights into the flow physics of flash floods. Field- and experiment-based research studies over complex topography are costly and limited by spatial scales and require a number of facilities and advanced instruments for high-
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