Dam failure and mammals

Brazil experienced the largest socioenvironmental catastrophe of its history, caused by a tailings dam failure, known as “Mariana disaster”. The wave of iron-mining waste buried villages, contaminated the Doce River, and left an immense ocean plume. The Doce River watershed is the largest in southeast Brazil, and located in the Atlantic Forest domain, presenting an outstanding economic, social, and biological relevance. Although the effects of such tragic events are usually assessed through fish assemblage changes, mammals have important effects on environment structure and regeneration. Inventories are of prime importance for adequate conservation efforts as well as for evaluating impacts of any disaster. Therefore, the aim of this paper was to present an updated assessment of mammalian list collected in the affected portion of Doce River before the dam failure therefore contributing to future conservation efforts. Data collection comprised specimens deposited in Museu Nacional/UFRJ, the oldest mammal collection of Brazil, and literature review. The two surveys together retrieved 157 species from 31 families and 11 orders, representing around 60% of the known mammalian diversity in the Atlantic Forest, including some in critical conservation condition, such as the Franciscana dolphin, the northern muriqui and the giant otter. Mining is a byproduct of present society, with dam breaches as a recurring problem. Facing the importance of Doce River to both Brazilian biodiversity and society, the chain of events must be taken into account in environmental rehabilitation strategies, and taxa less commonly assessed, like mammals, should be included.

The Market and Investors Reactions to Mariana’s and Brumadinho’s Environmental Disasters: Sentimental or Rational Decisions?

This research carried out event studies to analyze the reactions of the market and investors in Vale S.A. to the collapses of the Mariana and Brumadinho dams. It also assessed the extent to which the causes attributed to the market reactions to major disasters in previous research has helped to explain the reactions of the market and investors to the collapses of these dams. The analyses have shown that, in the case of the Fundão dam, there was a relevant reduction in the abnormal cumulative returns of common stocks and ADRs at the end of the eleven days of the collapse, despite the fact that the daily abnormal returns were not statistically significant. However, the abnormal trading volumes of these securities in the eleven days after the dam failure were generally negative and all statistically significant. In contrast, concerning the collapse of the Brumadinho dam, the abnormal returns on common stocks and ADRs were negative, relevant, and statistically significant, and, after the eleven days, the losses were considerable. The abnormal trading volumes of the securities were all positive and statistically significant, but the reactions of ADR investors were more intense than those of investors in common stocks. Examining the causal attributions made previously, there are indications that the market and investor reactions to the failures of the two dams were probably derived from the expectation that Vale and the other companies involved would incur severe losses and high contracting costs in political processes that would follow to the disasters, and from the difficulty the investors have had to assess the magnitude of these losses and costs.

Modeling and Risk Analysis of Dam-Break Flooding in a Semi‐Arid Montane Watershed.

The risk related to embankment dam breaches needs to be evaluated in order to prepare emergency action plans. The physical and hydrodynamic parameters of the flood wave generated from dam-failure event correspond to various breach parameters such as width, slope and formation time. This study aimed to simulate dam-breach failure scenario of Yabous dam (NE Algeria) and analyze its influence on areas (urban and natural environments) downstream the dam. The simulation was completed using the sensitivity analysis method in order to assess the impact of breach parameters on the dam-break scenario. The propagation of flood wave associated to dam-break was simulated using the one-dimensional HEC-RAS hydraulic model. This study ap-plied a sensitivity analysis of three breach parameters (slope, width, and formation time) in five sites selected downstream the embankment dam. The simulation showed that the maximum flow of the flood wave recorded at the level of the breach was 8768 m3/s, which gradually attenuated along the river course to reach 1579.2m3/s at about 8.5km downstream the dam. This study estab-lished the map of flood-prone areas that illustrated zones threatened with the flooding wave trig-gered by the dam failure due to extreme rainfall events. The sensitivity analysis showed that flood wave flow, height and width revealed positive and similar changes for the increase in adjustments (±25% and ±50%) of breach width and slope in the 5 sites. However, flood wave parameters of breach formation time showed significant trends that changed in the opposite direction compared to breach slope and width.

Assessment of Recent Flow, and Calving Rate of the Perito Moreno Glacier Using LANDSAT and SENTINEL2 Images

We mapped flow velocity and calving rates of the iconic Perito Moreno Glacier (PMG), belonging to the Southern Patagonian Icefield (SPI) in the Argentinian Patagonia. We tracked PMG from 2001 to 2017, focusing mostly upon the latest images from 2016–2017. PMG delivers about ca. 106 m3 day−1 of ice in the Lago Argentino, and its front periodically reaches the Peninsula Magallanes. Therein, the PMG causes an ice-dam, clogging Brazo Rico channel, and lifting water level by about 10 m, until ice-dam failure, normally occurring in March. Here, we used 36 pairs of satellite images with a resolution of 10 m (SENTINEL2, visible, 9 pairs of images) and 15 m (LANDSAT imagery, panchromatic, 27 pairs of images) to calculate surface velocity (VS). We used Orientation Correlation technique, implemented via the ImGRAFT® TemplateMatch tool. Calving rates were then calculated with two methods, namely, (i) M1, by ice flow through the glacier front, and (ii) M2, by ice flow at 7.5 km upstream of the front minus ablation losses. Surface velocity ranged from about 4 m day−1 in the accumulation area to about 2 m day−1 in the calving front, but it is variable seasonally with maxima in the summer (December–January–February). Calving rate (CRM) ranges from 7.72 × 105 ± 32% to 8.76 × 105 ± 31% m3 day−1, in line with recent studies, also with maxima in the summer. We found slightly lower flow velocity and calving rates than previously published values, but our estimates cover a different period, and a generally large uncertainty in flow assessment suggests a recent overall stability of the glacier.

Scenario Simulation of The Geohazard Dynamic Process of Large-Scale Landslides: A Case Study of The Xiaomojiu Landslide Along The Jinsha River

Large-scale landslides often cause severe damage due to their long run-out distances and having disaster chain effects. Scenario simulation has been adopted in the current work to analyze the Xiaomojiu landslide dynamic processes, such as sliding velocity, deposition characteristics, and flood outburst after a landslide-dam failure using Particle Flow Code (PFC-3D) which introduced the changeable friction coefficient and the HEC-RAS software. The landslide characteristics and topography data were obtained via field investigation, whereas high-resolution topographic data (0.17 m) was obtained using an Unmanned Aerial Vehicle (UAV). The results showed that: 1. The landslide presents a scallop shape with a length of 1566 m, a width ranging from 809~1124 m, and an area of 1.34×106 m2. The average thickness and volume of the sliding body is approximately 40 m, 5.1×107 m3. The InSAR deformation analysis showed that the Xiaomojiu landslide has a maximum annual displacement rate of 60 mm/y, and a maximum accumulation deformation of 180 mm since November 25, 2017. 2. From the landslide simulation results, the failure process of the Xiaomojiu landslide lasted for 65 s with a maximum velocity of 78.2 m/s. The deposited area is approximately 2023 m long, 900 m wide, with a maximum height of approximately 149 m. 3. After the landslide blocks the Jinsha River, a landslide-dammed lake with an elevation of 2940 m and a storage capacity of 4.13×109 m3 is formed. The maximum peak flow rate of the breach is 12051.7 m3/s, 43451.4 m3/s, 148635.6 m3/s, and 304544.7 m3/s for the landslide-dammed failure degrees of 15%, 25%, 50%, and 75%, respectively. These results provide a scientific reference for the risk analysis and mitigation of the landslide.