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The transport of coarse sediment during floods often exhibits hysteresis patterns from changes in flow fields, channel geometry, bedforms, or sediment supply conditions. Flume experiments that simulate hydrographs tend to confirm that hysteresis is a consequence of the progressive organization of surface sediments in terms of grain protrusion, imbrication, orientation, and roughness. Hysteretic patterns are also highly dependent on the kind of sediment supply conditions, and the type of simulated hydrograph. A factor that has not been investigated extensively is the effect of the timing and sequencing of floods on bedload transport. Depending on its magnitude and duration, each flood leaves the channel bed in a different condition, which influences the bedload transport of the next event, representing the river bed's memory of past floods, which can determine future responses to natural disturbances. In this study, I investigated the effects of different sequences of events, i.e., the flood history, on sediment transport through a series of flume experiments that simulated three types of stepped and symmetrical hydrographs (ranging from short-duration/high-magnitude to long-duration/low-magnitude events) under sediment recirculation conditions. Hydrographs were simulated as a sequence of the same event, and with events in different sequences, in order to explore the effects of different antecedent conditions on sediment transport. The results show that a previous event decreases the rates of sediment transported by a certain hydrograph by around 40% if a high-magnitude event precedes another one and around 70% if a low-magnitude event precedes another event of similar magnitude. A low-magnitude event does not affect the rate of sediment transported by a subsequent high-magnitude flood, but a high-magnitude event reduces the sediment transported by a subsequent long-duration/low-magnitude event. [ABSTRACT FROM AUTHOR]

There are many camping and recreation area located along two sides of Xiayun creek, Fuxing District of Taoyuan City, Taiwan. Recently, extremely rainfall events frequently occur in Northern Taiwan, local government increasingly cares about people's safety in recreation area during typhoon season.After collecting the information of topographic map, grain size distribution, scale and location of structures of check dam and grounsill. To evaluate the disaster risk, this study uses RiverFlow2D to simulate the rainstorm pattern of different reoccurrence frequency years of the Xiayun-creek watershed.By simulate the situation of the water level rises, to analyze the different river width whether it can affect the camping and recreation area, we can explore the dangerous location and associated precaution works. [ABSTRACT FROM AUTHOR]

Due to its particular position in the middle of the Mediterranean Sea and its complex andsteep orography, the Calabrian peninsula (southern Italy) is frequently affected by severeprecipitation events and is particularly prone to significant ground effects. In the earlyafternoon of August 20, 2018, a storm cell caused a flash flood that affected the smallRaganello Creek, in the northern side of the region, causing 10 casualties at the outlet of theRaganello Gorges, where the extension of the catchment is about 100 km2. Though theregional monitoring network is rather dense, in the surroundings of the disaster site raingauges were not able to measure the very intense and highly localized rainfall. However, thethree-hour Surface Rainfall Total (SRT) provided by a single polarization Doppler radar ofthe Italian National Radar Network showed a storm cell with rain peaks of theorder of 70-100 mm/hour in a small mountain area not covered by the monitoringnetwork. The objective of this work is to evaluate the ability of the state-of-the-artmeteorological/hydrological modelling in simulating the Raganello Creek event using bothone-way and fully-coupled approaches, by means of the WRF/WRF-Hydro modellingsystem. The Advanced Research WRF (ARW) Model, version 3.9.1 is used with two one-waynested domains at the resolution of 10 km and 2 km respectively, while the resolution ofthe hydrological model, based on WRF-Hydro version 5.0, is 200 m. The initialand boundary conditions are provided by the ECMWF’s Integrated ForecastingSystem (IFS), in its deterministic forecast version at 9 km resolution. Several WRFsimulations have been carried out, before choosing the best configuration, to testthe impact of the initial conditions, horizontal resolutions and parameterizationschemes. Results show that the model, particularly in its fully-coupled version, is able to predictreasonably well the occurrence of the event both in terms of rainfall, thus identifying thestorm cell, and in terms of hydrological impact, reproducing timely what mighthave been (unfortunately, observed runoff is not available) the event hydrograph. [ABSTRACT FROM AUTHOR]

Every year thousand people suffer from dangerous hydrological events like floods and debris flows all over the world. The aim of this research was to calculate characteristics of these hazards such as maximum discharges of the flows, water-levels and cross-sectional areas, which are necessary for defense construction designing. The first object of our research was the river Vladimirovka, the right tributary of the river Susuya. This river is situated in Sakhalin region near Yzhno-Sakhalinsk, one of the largest cities there. Despite the fact that disastrous debris flows were observed for more than last 10 years, flash floods are much more frequent events for the territory. During the research we applied the model of unsteady water movement, which was developed in Saint Petersburg State University (Vinogradova and Nikiforovskaia, 2015). Basis of the model is the solution of an one-dimensional set of equations of Saint-Venant. For this purpose, the numerical scheme developed in Institute of Hydrodynamics from Academy of Sciences of the USSR (IH) was used. The calculations were carried out with different probability of flows like 10, 1 and 0.1 percent. Due to the fact that there is no calibration block in the model and code of roughness is a functionally dependent parameter, we conducted several numerical experiments to clarify maximum values. For estimation parameters of flood, we chose the Porus river, located in Novgorod region, in which a disastrous event occurred in April 2017. Special field measurements such as hydraulics-morphometric were carried out by LLC "NPO" Gidrotekhproekt "in 2017 according to a design specification. To sum up, this research provided characteristics of floods and debris flows, which could be used for protection of the territory. [ABSTRACT FROM AUTHOR]

Flood-related economic losses have increased dramatically over the past decades in most parts of the world, and are expected to increase in the future due to climate dynamics and increasing exposure. From a practical perspective, it is of interest to estimate the probability of large flood events to happen at a certain location or region (i.e., flood hazard estimation). From a theoretical perspective, it is of interest to understand how the flood hazard depends on the causal mechanisms and dominant processes in the atmosphere, catchment, and river system. The talk will link these practical and theoretical perspectives arguing that understanding flood processes at different temporal scales, from events to centuries, is valuable for estimating the river flood hazard reliably, especially if one expects the landscape and/or climate to change in the future. [ABSTRACT FROM AUTHOR]

River flooding is a common hazard, causing billions of dollars in annual losses. The impacts of floods are shaped by the spatial scale over which different rivers flood simultaneously. We use flood data from several thousand European rivers to demonstrate that the flood synchrony scale – the distance over which multiple rivers flood near-synchronously – far exceeds the size of individual drainage basins, and varies regionally by more than an order of magnitude. We also show that flood synchrony scales have grown by about 50% over the period 1960-2010, and that years with spatially extensive floods tend to follow one another. These findings reveal that flood risks are correlated well beyond the individual drainage basins for which flood hazards are typically assessed and managed. [ABSTRACT FROM AUTHOR]