When it rains in the desert of Patagonia: heavy rains, sediment laden flash floods and hazard management challenges.

Ephemeral streams in dry environments can produce high intensity sediment-laden flash floods. The research of these events is quite difficult due to far locations with limited accessibility, unexpected events, and rough weather conditions. Hence combined data of rainfall, flood hydrograph and sediment transport is rather scarce in the world. Recent extreme events (RI > 550 years) in arroyos (ephemeral streams) of the central Patagonia (Argentina) has called the attention of public and scientific community. The Sagmata basin (total drained area of 129 km2), located in the Lower Valley of the Chubut River (Province of Chubut, Argentina) has been equipped with 4 raingauges, a weather station, four cameras and sediment sampler in four reaches of the arroyos. Data from a two-year monitoring provides valuable insights about the hydrological response of basins in Patagonia, such as the time of response, the shape of hydrographs and its relations with the hyetographs and duration curves. The arroyos are wetted a short period of the time (8 to 21 hours a year). Single-peak, multi-peak and flat top hydrographs have been observed. The lag-time decreases with the increase of the rainfall intensity and the maximum water stage. Moreover, the bore front moves with mean speed which value is between 0.8 to 1.6 m s-1. The wash load in the arroyos depends on geological settings and vegetation cover of the basin. Mean values are between 23 – 46 gr l-1. The complex hydrograph shape produced by the basin has been linked to the rainfall features (duration, mean intensity and patchiness) and the basin physiography of the basin. Findings from the present study provide valuable information both for the comprehension of arroyos in drylands and hazard management as well.

Temporary dependency of parameter sensitivity for different flood types

Hydrological and climatic data at finer temporal resolutions are considered essential to model hydrological processes, especially for short duration flood events. Parameter transferability is an essential approach to obtain sub-daily hydrological simulations at many regions without sub-daily data. In this study, the objective is to investigate temporary dependency of parameter sensitivity for different flood types, which contributes to research of parameter transferability. This study is conducted in a medium-sized basin using a distributed hydrological model, DHSVM. Thirty-six flood events in the period of 04/12/2006–07/01/2013 in the Jinhua River basin, China, are classified into three flood types (FF: flash flood, SRF: short rainfall flood and LRF: long rainfall flood) by using the fuzzy decision tree method. The results show that SRF is the dominant flood type in the study area, followed by LRF and FF. Runoff simulations of FF and SRF are more sensitive to parameter perturbations than that of LRF. Sensitive parameters are highly dependent on temporal resolutions. The temporary dependency of LRF is the highest, followed by SRF and FF. More attention should be payed to sensitive and highly temporal dependent parameters in a subsequent parameter transfer process. Further study referring this result is required to test the applicability.

Massflow—A software for dynamic modeling and risk evaluation of earth-surfaced flow

<p>Massflow is based on the depth-integrated continuum and solved by second-order MacCormack-TVD finite difference method. Shared code and friendly GUI are provided for researchers and engineers. It adopted CPU and GPU accellerated algorithm to improve the efficiency. Now around 1000 people adopted Massflow to do their own research. Based the framework, we have done several insightful simulations of real landslides and debris flows. Meanwhile, we are developing a solution for catchment-based rainfall- flood-debris flow prediction. We will introduce the basic of the software, the mechanism and related model to modeling the real hazards, and the framework and finished work of forecasting of catchment flood or debris flow. </p>

Rapid Flood Mapping Using Multi-temporal SAR Images: An Example from Bangladesh

In the HKH region, large areas in Afghanistan, Bangladesh, China, India, Myanmar, Nepal, and Pakistan get inundated by floodwater during every rainy season. Among them, Bangladesh has been experiencing record-high floods where four types prevail: flash flood, local rainfall flood, monsoon river flood, and storm-surge flood; and these occur almost every year due to Bangladesh’s unique geographical setting as the most downstream country in the HKH region.

Comparison of Floods Driven by Tropical Cyclones and Monsoons in the Southeastern Coastal Region of China

Increasing evidence indicates that changes have occurred in heavy precipitation associated with tropical cyclone (TC) and local monsoon (non-TC) systems in the southeastern coastal region of China over recent decades. This leads to the following questions: what are the differences between TC and non-TC flooding, and how do TC and non-TC flooding events change over time? We applied an identification procedure for TC and non-TC floods by linking flooding to rainfall. This method identified TC and non-TC rainfall–flood events by the TC rainfall ratio (percentage of TC rainfall to total rainfall for rainfall–flood events). Our results indicated that 1) the TC rainfall–flood events presented a faster runoff generation process associated with larger flood peaks and rainfall intensities but smaller rainfall volumes, compared to that of non-TC rainfall–flood events, and 2) the magnitude of TC floods exhibited a decreasing trend, similar to the trend in the amount and frequency of TC extreme precipitation. However, the frequency of TC floods did not present obvious changes. In addition, non-TC floods decreased in magnitude and frequency while non-TC extreme precipitation showed an increase. Our results identified significantly different characteristics between TC and non-TC flood events, thus emphasizing the importance of considering different mechanisms of floods to explore the physical drivers of runoff response. Also, our results indicated that significant decreases occurred in the magnitude, but not the frequency, of floods induced by TC from the western North Pacific, which is the most active ocean basin for TC activity, and thus can provide useful information for future studies on the global pattern of TC-induced flooding.