Abstract The exploited mangrove crab Ucides cordatus, an important ecosystem engineer in South American mangroves, has a biphasic lifecycle with pelagic larvae developing offshore. Megalopae return to the mangrove forest to settle, i.e., metamorphose into benthic juveniles but its environmental drivers remain poorly understood. We postulate that conspecific crabs facilitate recruitment. In the field, we investigated whether the number of recruits is higher near conspecific burrows than in areas without conspecific bioturbation. Recruit sampling was conducted monthly from April 2008 to May 2009 along an environmental gradient. First, U. cordatus recruits of that year emerged from March to July. Intraspecific facilitation was indicated by significantly higher recruit numbers in bioturbated than in non-bioturbated substrates. Recruits were most abundant in zones with intermediate conditions of inundation, leaf litter standing stock, sediment consistency, luminosity, temperature, salinity, and pH. Avoidance of more inundated zones likely reduces predation by fishes and of less inundated zones helps individuals escape more stressful, drier environmental conditions. The observed habitat-specific recruitment pattern must be considered when designing field assessments of the population structure of U. cordatus (which should include sampling recruits) and enhancing stocks by releasing laboratory-cultivated larvae and first juveniles into the wild. mangroves offshore settle ie i e i.e. understood bioturbation 200 gradient First U July nonbioturbated non substrates inundation stock consistency luminosity temperature salinity pH stressful habitatspecific habitat specific which laboratorycultivated laboratory cultivated wild i.e 20 2

We report radiocarbon dates obtained from on-shore marine and near-shore terrestrial deposits near Yzerfontein, on the West Coast of South Africa. These deposits include Late Pleistocene shell concretions from the southern end of 16 Mile Beach and a marine shell deposit inland of the coastal Rooipan (Red Pan); mid-Holocene coastal pan deposits exposed by modern storm erosion of the sandy 16 Mile Beach; and four Holocene storm beach deposits on a rocky shore to the south. We interpret the results in terms of local geomorphology constraints on sea-level fluctuations. The eastern margin of Rooipan is a >40 ka elevated beach deposit in a dune cordon that separates it from the adjacent Yzerfonteinpan. Both pans have gypsum deposits up to 2 m thick formed by repeated marine overwash. Saline pan deposits that are exposed intermittently on the beach are mid-Holocene and indicate a former westward extension of Rooipan. This is in contrast to storm beaches dating 8000-2600 cal BP at higher elevations on a rocky platform further south. This suggests that a dune barrier existed seaward of the present shoreline near Rooipan at this time. The coastal changes described here show that deposition and erosion can be affected significantly by the local palaeogeomorphology and cannot be ascribed solely to sea-level change. SIGNIFICANCE: Mollusc shells from Yzerfontein, Western Cape Province, South Africa, show radiocarbon ages ranging from >40 000 years to a few decades before present. There is evidence for elevated sea levels between 8000 and 2600 years ago, and sea levels similar to the present in the last 2000 years. Neither the elevation of the deposits nor their ages conform to published sea-level change curves for the Western Cape coast. Inundation by rising sea levels in the Holocene was not spatially uniform. Former and present geomorphology have had a significant effect on deposition and preservation of indicators of sea-level change.

Abstract Delimitation of areas subject to flooding is crucial to understand water dynamics and fluvial changes. This study analyzed the potential of C-band Synthetic Aperture Radar (SAR) images acquired by the Sentinel-1 satellite in 2017, 2018, and 2019 to delineate flooded areas in the Central Amazon. The images were processed by the Artificial Neural Network Multi-Layer Perceptron (ANN-MLP) and two K-Nearest Neighbor (KNN-7 and KNN-11) machine learning (ML) classifiers. Pre-processing of Single Look Complex (SLC) SAR images involved the following methodological steps: orbit-file application; radiometric calibration (σ0); Range-Doppler terrain correction; speckle noise filtering; and conversion of linear data to backscattering coefficients (units in dB). We applied the Lee filter, with a window size of 3x3, for speckle filtering. A set of 6000 randomly distributed samples for training (70%), validation (20%), and test (10%) was obtained based on visual interpretation of Sentinel-2 optical satellite image acquired in the same years of SAR images. We found the largest flooded areas in 2019 in the study area (municipality of Parintins and Urucará, Amazonas River, Brazil): 6244km2 by the ANN-MLP classifier; 6268km2 by KNN-7; and 6290km2 by KNN-11, while the smallest flooded areas were found in 2018: 5364km2 by ANN-MLP; 5412km2 by KNN-7; and 5535km2 by KNN-11. The three classifiers presented Kappa coefficients between 0.77 and 0.91. ANN-MLP showed the best accuracy. The presence of shadow effects in the SAR images increased the commission errors.

Resumo A delimitação de áreas sujeitas a inundações é crucial para entender a dinâmica hídrica e as mudanças fluviais. Este estudo analisou o potencial de imagens de radar de abertura sintética (SAR) adquiridas na banda-C pelo satélite Sentinel-1 em 2017, 2018 e 2019 para delinear áreas inundadas na Amazónia Central. As imagens foram processadas pela Rede Neural Artificial Multi-Layer Perceptron (RNA-MLP) e dois classificadores de aprendizagem de máquina (ML) K-Nearest Neighbor (KNN-7 e KNN-11). O pré-processamento de imagens SAR Single Look Complex (SLC) envolveu as seguintes etapas metodológicas: aplicação do orbit-file; calibração radiométrica (σ0); correção de terreno Range-Doppler; filtragem de ruído speckle; e conversão de dados lineares para coeficientes de retroespalhamento (unidades em dB). O filtro de Lee com tamanho de janela de 3×3 foi aplicado para filtragem do ruído speckle. Um conjunto de 6000 amostras distribuídas aleatoriamente para treino (70%), validação (20%) e teste (10%) foi obtido com base na interpretação visual da imagem do satélite óptico Sentinel-2 adquiridas no mesmo ano das imagens de radar. As maiores áreas alagadas foram encontradas em 2019 na área de estudo (municípios de Parintins e Urucará, Rio Amazonas, Brasil): 6244km2 pelo classificador RNA-MLP; 6268km2 pelo KNN-7; e 6290km2 pelo KNN-11, enquanto as menores áreas alagadas foram encontradas em 2018: 5364km2 pelo classificador RNA -MLP; 5412km2 pelo KNN-7; e 5535km2 pelo KNN-11. Os três classificadores apresentaram coeficientes Kappa entre 0,77 e 0,91. A RNA-MLP apresentou a melhor precisão. A presença de efeitos de sombra nas imagens SAR aumentou os erros de comissão.

Résumé La délimitation de zones sujettes aux inondations est cruciale pour comprendre la dynamique hydrique et les changements fluviaux. Cette étude a analysé le potentiel des images radar à ouverture de synthétique (SAR) acquises en bande-C par le satellite Sentinel-1 en 2017, 2018 et 2019 pour délimiter les zones inondées en Amazonie Centrale. Les images ont été traitées par le Réseau de Neurones Artificiels Multicouches Perceptron (ARN-MLP) et deux classificateurs d'apprentissage automatique (ML) K-Nearest Neighbor (KNN-7 et KNN-11). Le prétraitement des images SAR images complexes à visée simple (SLC) a impliqué les étapes méthodologiques suivantes : application du fichier d'orbite; calibration radiométrique (σ0); correction de terrain Range-Doppler; filtrage du bruit de chatoiement; et conversion des données linéaires en coefficients de rétrodiffusion (unités en dB). Un filtre de Lee avec une taille de fenêtre de 3×3 a été appliqué pour filtrer le bruit de chatoiement. Un ensemble de 6000 échantillons assignés au hasard pour la formation (70%), la validation (20%) et les tests (10%) a été obtenu à partir de l'interprétation visuelle de l'image satellite optique Sentinel-2 acquise pour la même année que les images radar. Les plus grandes zones inondées ont été trouvées en 2019 dans la zone d'étude (municipalité de Parintins et Urucará, la Riviére Amazonas, Brésil) : 6244km2 selon le classificateur RNA -MLP; 6268km2 pour KNN-7; et 6290km2 pour KNN-11, alors que les plus petites zones inondées ont été trouvées en 2018: 5364km2 pour le classificateur RNA -MLP; 5412km2 pour KNN-7; et 5535km2 pour KNN-11. Les trois classifieurs présentaient des coefficients Kappa compris entre 0,77 et 0,91. L'ARN-MLP a montré une meilleure précision. La présence d'effets d'ombre dans les images SAR a augmenté les erreurs de commission.

Resumen La delimitación de áreas sujetas a inundaciones es crucial para comprender la dinámica del agua y los cambios fluviales. Este estudio analizó el potencial de las imágenes de radar de apertura sintética (SAR) adquiridas en la banda-C por el satélite Sentinel-1 en 2017, 2018 y 2019 para delinear áreas inundadas en la Amazonía Central. Las imágenes fueron procesadas por la Red Neuronal Artificial de Perceptrón Multicapa (RNA-MLP) y dos clasificadores de aprendizaje automático (ML) K-Nearest Neighbor (KNN-7 y KNN-11). El preprocesamiento de imágenes SAR complejas de una sola mirada (SLC) involucró los siguientes pasos metodológicos: aplicación del archivo de órbita; calibración radiométrica (σ0); corrección del terreno Range-Doppler; filtrado de ruido moteado; y conversión de datos lineales en coeficientes de retrodispersión (unidades en dB). Se aplicó El filtro Lee con un tamaño de ventana de 3×3 para filtrar el ruido moteado. Se obtuvo un conjunto de 6000 muestras asignadas aleatoriamente para entrenamiento (70%), validación (20%) y prueba (10%) en base a la interpretación visual de la imagen del satélite óptico Sentinel-2 adquirida el mismo año que las imágenes de radar. Los humedales más grandes se encontraron en 2019 en el área de estudio (municipio de Parintins y Urucará, Rió Amazonas, Brasil): 6244km2 por el clasificador RNA -MLP; 6268km2 por KNN-7; y, 6290km2 por KNN-11, mientras que, los humedales más pequeños se encontraron en 2018: 5364km2 por el clasificador RNA -MLP; 5412km2 por KNN-7; y 5535km2 por KNN-11. Los tres clasificadores presentaron coeficientes Kappa entre 0,77 y 0,91. RNA-MLP mostró la mejor precisión. La presencia de efectos de sombra en las imágenes SAR aumentó los errores de comisión.

ABSTRACT Despite of benefits such as water security and energy supply dams provide, there are environmental impacts and risks of accidents associated with their usage, i.e. rupture. In these cases, a structured Emergency Action Plan (EAP) must be executed to mitigate impacts and loss of life. To do so, hypothetical dam break scenarios must be simulated to obtain the flood’s spatial coverage in downstream valley. In this regard, this work aimed to obtain the flood maps due to hypothetical ruptures of Jacarecica I and Jacarecica II dams (state of Sergipe), structures that don’t have Safety Plans elaborated. HEC-RAS 2D model was used to elaborate flood inundation maps and assess hydrodynamic results, that showed the breach wave impacts residential, industrial and agricultural areas before reaching the city of Riachuelo, with high depths and velocities, and minimum arrival times of 6 hours. With rural and urban areas at risk, it is mandatory, according to the PNSB, that the dams’ EAPs are prepared. provide usage ie i e i.e rupture cases EAP (EAP life so floods s valley regard state Sergipe, Sergipe , Sergipe) dont don t elaborated HECRAS HEC RAS D results residential Riachuelo velocities hours risk mandatory PNSB prepared

RESUMO Apesar de benefícios como segurança hídrica e fornecimento de energia que barragens garantem, há impactos ambientais e riscos de acidentes associados ao seu uso, como o rompimento. Nesses casos, um Plano de Ação de Emergência (PAE) estruturado deve ser executado para mitigar os impactos ambientais e a perda de vidas. Para tanto, cenários hipotéticos de rompimento devem ser simulados para obter a mancha de inundação no vale a jusante. Nesse sentido, este trabalho teve como objetivo obter a mancha de inundação da ruptura hipotética das barragens Jacarecica I e Jacarecica II (estado de Sergipe), estruturas que não possuem Planos de Segurança elaborados. O modelo 2D HEC-RAS foi utilizado para elaborar as manchas de inundação e avaliar os resultados hidrodinâmicos, que mostraram que a onda de ruptura impacta áreas residenciais, industriais e agrícolas antes de atingir a cidade de Riachuelo, com altas profundidades e velocidades, e tempos de chegada mínimos de 6 horas. Com áreas rurais e urbanas em risco, é obrigatório, segundo a PNSB, que os PAEs das barragens sejam elaborados. garantem uso casos PAE (PAE vidas tanto jusante sentido estado Sergipe, Sergipe , Sergipe) elaborados D HECRAS HEC RAS hidrodinâmicos residenciais Riachuelo velocidades horas risco obrigatório PNSB

RESUMO A impermeabilização de áreas em centros urbanos, resultante do processo de ocupação desordenada do solo, contribui para o aumento e a aceleração do escoamento superficial e, consequentemente, para a ocorrência de enchentes e inundações em bacias urbanas. Nesse contexto, atualmente, modelos hidrológicos vêm sendo empregados no desenvolvimento de políticas públicas de gestão das águas urbanas, com vistas à drenagem urbana sustentável. O presente trabalho teve como objetivo usar um modelo hidrológico para a bacia do ribeirão Vai e Volta, localizada no município de Poços de Caldas, Minas Gerais, para simular o hidrograma de cheia em um canal urbano. Utilizou-se o software Storm Water Management Model (SWMM) calibrando o modelo a dados de chuva e vazão medidos. Realizou-se a calibração manual do modelo para dois eventos de precipitação com a obtenção do coeficiente de eficiência de Nash-Sutcliffe (NSE) médio de 0,73 e erros da vazão de pico e do volume escoado inferiores a 15%. O modelo foi validado para outros três eventos distintos e obteve-se ajuste NSE médio de 0,79 e erros da vazão de pico e do volume escoado inferiores a 5%.

ABSTRACT The waterproofing of areas in urban centers, resulting from the disorderly occupation of the soil, contributes to increase and accelerate the runoff and, consequently, to the occurrence of floods and inundation in urban watersheds. In this context, hydrological models are currently being used in the development of public policies for urban water management, related to sustainable urban drainage. The present work aimed to use a hydrological model for the watershed of the Vai e Volta stream, located in the city of Poços de Caldas, Minas Gerais, to simulate the flood hydrograph in an urban open channel. The Storm Water Management Model (SWMM) software was used, calibrating the model to measured rainfall and flow data. The model was manually calibrated for two rainfall events with an average Nash-Sutcliffe coefficient (NSE) of 0.73 and errors in peak flow and runoff volume below 15%. The model was validated for three other distinct events and an average NSE adjustment of 0.79 was obtained and errors in peak flow and runoff volume below 5%.

The monitoring of wetland extent is a global imperative, considering loss of ecosystem services and conservation value. To date, the understanding of the variation in the extent of lacustrine (inundated) wetlands has been limited, based on intermittently available, coarse-scale imagery. The aim of this study was to assess the capabilities of the freely available Sentinel-2 sensor in monitoring inundated wetlands. In particular, to demonstrate the ability to determine the maximum extent of inundation for reporting on the Sustainable Development Goal (SDG) 6.6 (Clean Water and Sanitation) and SDG 15.1 (i.e., halting biodiversity loss), the functional diversity and the hydrological regime of depressions were explored in the Mpumalanga Lake District (MLD) of South Africa. Using the monthly inundation data derived from Sentinel-2 images between January 2016 and May 2018, the results showed that the maximum extent of open water can be successfully reported for SDG 6.6. Lacustrine wetlands constituted about 47 of the 416 (but 66% of the total areal extent of) depressions in the MLD, while others were predominantly palustrine (vegetated). The functional diversity varied from predominantly (61% of the extent of) inundated depressions to seasonally (3%) inundated depressions. The Sentinel-2 sensor was able to detect intra- and inter-annual variation of the extent of inundation, making it suitable to monitor these wetlands for global and climate change impacts.

This article discusses the reliability of flood inundation information that is obtained from participatory mapping. The commonly applied method to map flood inundation requires both direct and interpretive measurement data based on remote sensing images. Such assessments have limited availability of data; as a result, participatory mapping has become the solution. A number of studies have conducted participatory mapping to obtain flood hazard information in areas with limited sources of data, however, there has been little discussion about its reliability. This research conducted participatory flood inundation mapping by involving local leaders as respondents. The mental map drawn by the local leaders was digitised to obtain a shapefile format map. The information obtained from the semistructured interview was then included in the geographic information system (GIS) data as attributes. The obtained information was compared with the field data to determine its quality. A literature study was then conducted to discuss how the participatory mapping could support managing a disaster. Information obtained through participatory mapping can be effectively applied to disaster management because of its precise location information, lower cost and less time-consuming nature. The reliability of the information has weak accuracy of quantitative data; however, it has advantages in terms of qualitative data, especially in the detailed descriptions of flood information. In the future, participatory mapping should rely on integrating the perspectives of cross-disciplinary researchers, a comprehensive study of multidisciplinary knowledge and level of understanding of the stakeholders.

Resumen Después del terremoto de Limón, Costa Rica del 22 de abril de 1991 (Mw 7.7) se observó un pequeño tsunami (magnitud, m~ 1) a lo largo de la costa caribeña de Costa Rica y Panamá. Este informe resume las observaciones de testigos oculares de 26 sitios a lo largo de 150 km de costa afectada desde río Matina, Costa Rica hasta Bocas del Toro, noroeste de Panamá, así como mareogramas registrados en Panamá, Puerto Rico y las Islas Vírgenes. No se emitieron advertencias de emergencia antes de que ocurriera el tsunami. Aunque se reportaron pocos o ningún daño a la propiedad relacionada con el tsunami, dos o más ahogamientos fueron atribuidos al tsunami. La altura máxima de las olas fue de 2 a 3 m, y la inundación y las inundaciones costeras se extendieron hasta 200 m tierra adentro en algunos lugares. Tanto la elevación costera cosísmica como la presencia de arrecifes marinos parecen haber proporcionado protección contra los principales efectos del tsunami en algunas zonas costeras. En otros lugares, los efectos de las olas se amplificaron en las desembocaduras de los ríos debido a la compactación diferencial de sedimentos no consolidados. La deposición generalizada de arena de tsunami cerca de la frontera Costa Rica-Panamá en 1991 es similar a la deposición asociada con el terremoto y tsunami del 7 de mayo de 1822.

Abstract A small tsunami (tsunami magnitude, m ~ 1) was observed following the 22 April 1991 Mw 7.7 Limón, Costa Rica earthquake along the Caribbean coast of Costa Rica and Panama. This report summarizes eyewitness observations from 26 sites along 150 km of affected coast from Rio Matina, Costa Rica to Bocas del Toro, Northwestern Panama, as well as tide gauge recordings from Panama, Puerto Rico and the Virgin Islands. No emergency warnings were issued before the tsunami occurred. While little or no tsunami-related property damage was reported, two or more drownings were attributed to the tsunami. The maximum runup/wave height was reported to be 2 to 3 m, and inundation and coastal flooding extended up to 100 m inland in some locations. Both coseismic coastal uplift and the presence of fringing offshore reefs appear to have provided protection against major runup effects in some coastal areas. Elsewhere, runup effects were amplified at river mouths due to differential compaction of unconsolidated sediments. Widespread tsunami sand deposition near the Costa Rica-Panama border in 1991 is similar to deposition associated with the 7 May 1822 earthquake and tsunami.

Resumen: En Costa Rica, pese a su relativa baja frecuencia, los tsunamis suponen un riesgo en las comunidades costeras. La integración de información geofísica y geológica permite la interpretación de posibles áreas de ruptura para las cuales se evalúa la propagación e inundación de tsunamis a través de simulaciones numéricas en el Caribe de Costa Rica y zonas adyacentes al sismo tsunamigénico ocurrido en 1991 (Mw 7,7). Los resultados muestran que el peligro de inundación por tsunamis en el Caribe de Costa Rica devenga particularmente de sismos generados en el Cinturón Deformado del Norte de Panamá. Además, se muestra que sismos de mediana magnitud (Mw~7) en fallas de alto ángulo, pueden provocar tsunamis locales. Este trabajo puede ser usado como base para la generación de mapas de evacuación y concientización del peligro de tsunamis en la zona.

Abstract In Costa Rica, despite their relative low frequency, tsunamis could pose risk to coastal communities. The integration of geophysical and geological information allows the interpretation of possible rupture areas for which tsunami propagation and inundation is evaluated through numerical modeling along the Caribbean of Costa Rica and areas adjacent to the tsunamigenic earthquake that occurred in 1991 (Mw 7,7). The results show that the tsunami threat in the Caribbean of Costa Rica arises particularly from earthquakes generated in the North Panama Deformation Belt. In addition, it is shown that medium-magnitude earthquakes (Mw ~ 7) in high-angle faults can cause local tsunamis. This work can be used as a basis for the generation of evacuation maps and awareness of the tsunami threat in the area.

For the first progress reporting on the Sustainable Development Goal sub-indicator 6.6.1a in 2020, the South African and global statistics related to wetlands were compared. Firstly, in terms of the total wetland extent, the South African National Wetland Map version 5 (NWM5) represented 87% more inland, surface aquatic ecosystems than the Global Surface Water (GSW) product. More than half of the lacustrine systems and none of the palustrine and arid systems in NWM5 are represented in the GSW layer. Secondly, in terms of changes in the extent of wetlands, both the global and South African statistics showed a decreasing trend in the spatial extent of surface aquatic ecosystems in South Africa. These trends should be further investigated against systematic assessments of decadal drought periods. The hydroperiod information (permanent, seasonal and ephemeral inundation periods) of the GSW products show that South African lacustrine wetlands do not have a single dominant class (>70% of the extent of a polygon) of inundation, but consist of a mosaic of these classes.SIGNIFICANCE: • The South African National Wetlands Map version 5 represents 87% more of the extent of lacustrine, palustrine and arid wetlands than the Global Surface Water products that are used for progress reporting on the Sustainable Development Goal sub-indicator 6.6.1a. • South African and global statistics suggest a decline in the extent of lacustrine wetlands, although a systematic comparison with decadal drought periods is required to confirm these trends. • South African lacustrine wetlands consist of a mosaic of hydroperiod classes (permanent, seasonal and ephemeral inundation periods) with no individual class dominating (>70% of the extent of) wetlands polygons.

ABSTRACT The rice (Oryza sativa L.) crop is very important worldwide for its contribution to human nutrition. Rice grain yield depends on several agronomic management factors that must also be adjusted to the cropping system such as permanent inundation (anaerobic conditions) or direct seeding (aerobic and anaerobic conditions) mainly in response to the application of nutrients such as N. In Chile, the cropping system with direct seeding has limited agronomic and scientific development. The objective was to determine the effect of increasing N (0, 40, 80, 120, and 160 kg ha-1), P (0, 30, 60, and 120 kg P2O5 ha-1), and K (0, 30, 60, and 120 kg K2O ha-1) rates on grain yield and N agronomic efficiency (NAE) (kg grain produced per kg N applied) in two paddy rice soils for two consecutive seasons. Grain yield had a positive response to increasing N rates in the two evaluated soils (grain yield increased from 6.7 to 8.9 Mg ha-1 in the Vertisol and from 7.4 to 11.0 Mg ha-1 in the Alfisol) and a low response to P rates in the Vertisol. The Alfisol showed no response to increasing P rates, and both soils had no response to K application. The N rates that obtained the highest rice grain yield were 120 and 160 kg ha-1 for Alfisol and Vertisol, respectively. The P rate that obtained the highest rice yield in the Vertisol was 30 kg ha-1 P2O5. In addition, NAE values associated to those N rates were 74 and 61, respectively. In conclusion, direct seeding in rice cropping had a response to high rates of applied N, low response to P, and no response to K.

Abstract Pondicherry located on the southeast coast of India was largely affected by the 26 Dec 2004 tsunami. However, a few regions along the Pondicherry coast did not experience any inundation/damage. In this study, we have considered three regions along the Pondicherry coast, namely (1) Auroville Beach (2) Beach Road, and (3) Paradise Beach. Combining SRTM, CMAP, and GEBCO data a high resolution topographic and bathymetric data is acquired for the study region. Tsunami wave heights and inundation extent is calculated using the TUNAMI N2 model in the study region. It is observed that the structures on the Beach Road of Pondicherry were untouched and almost no inundation occurred in this region due to the rock boulders situated along the coast during the 2004 Indian Ocean Tsunami. The Auroville Beach, having a steep slope, and the Paradise Beach, which is relatively flat is also studied for the tsunami wave-heights and inundation due to the variation in their topography. A sea wall of the same height as the boulders is considered to estimate the inundation along the Beach Road. Also, the surge forces are calculated along the sea wall. Results reveal that the tsunami wave heights and inundation at Auroville beach are much less than the Paradise beach, whereas there was no inundation along the Beach Road. Usage of rock boulders along populated coastal areas can minimize the damage due to tsunami.

Resumen El 26 de diciembre de 2004 la ciudad de Pondicherry, ubicada en la costa sureste de la India, se vio afectada por un tsunami. Regiones aledañas a lo largo de la costa no experimentaron inundaciones ni daños, situación que es valorada en el presente trabajo. Se estudiaron tres regiones a lo largo de la costa de Pondicherry a saber: (1) Playa de Auroville, (2) Calle costera, y (3). Playa Paraíso mediante el método de combinación de datos SRTM, CMAP y GEBCO, a través de información topográfica y batimétrica de alta resolución. La altura de las olas del tsunami y la extensión de la inundación se calculan utilizando el modelo TUNAMI N2 en la región de estudio. Se observa que las estructuras en la Calle costera de Pondicherry estaban intactas y casi no se produjeron inundaciones en esta región debido a los cantos rodados situados a lo largo de la costa durante el tsunami del Océano Índico de 2004. También se estudiaron las playas de Auroville (que tiene una pendiente pronunciada), y Paradise (que es relativamente plana) en relación a las alturas de las olas y el alcance de las inundaciones. Se considera que el malecón de la misma altura que los cantos rodados de las playas previas dan pauta de las fuerzas de oleaje. Los resultados revelan que las alturas de las olas del tsunami y la inundación en la playa de Auroville es mucho menor que en la playa Paradise, mientras que no hubo inundaciones a lo largo de la Calle Costera, destacándose que el uso de cantos rodados a lo largo de áreas costeras pobladas puede minimizar los daño debido a tsunamis.

RESUMO Neste trabalho, foi utilizado o Modelo de Grandes Bacias (MGB-IPH) para simular a propagação de um hidrograma de ruptura estimado a partir de equações preditoras para a barragem da UHE Três Marias, considerada uma das maiores da América do Sul. Os resultados, quanto à vazão de pico, tempo de pico e mancha de inundação foram comparados com os resultados advindos do modelo Hec-Ras 5.06, tipicamente utilizado para estudos de rompimento de barragens em escala local. Quanto à extensão da mancha de inundação, obteve-se um índice de acerto de 84% e um erro mediano de 2,1 metros de profundidade, ao longo de 4.055 km2 de área inundada a jusante. Observaram-se erros máximos de 13% na predição da vazão de pico e de 20% para o tempo de pico em locais distantes até 526 km a jusante da barragem, estabelecendo-se, portanto dentre os limites das incertezas típicas associadas a estudos de rompimento de barragens. Desta forma, o uso potencial deste tipo de abordagem em estudos prévios de rompimento de barragens é explorado, configurando-se este método como uma alternativa ao uso de modelos robustos ou simplificados para determinação de áreas de jusante potencialmente afetadas por estes desastres.

ABSTRACT In this research study, the MGB-IPH (acronym for Large Scale Model in Portuguese - Modelo de Grandes Bacias) was used to simulate the propagation of a dam breach hydrograph estimated from predictor equations for the Três Marias Hydropower Dam, considered one of the largest in South America. The results of the peak flow, peak time and flood spot were compared with results of the Hec-Ras 5.06 model, typically used for local-scale dam break studies. As for the extent of the flood, a hit rate of 84% and a median error of 2.1 meters deep, along 4,055 km2 of the flooded area downstream was obtained. Maximum errors of 13% were observed in the prediction of the peak flow and of 20% for the peak time in distant locations up to 526 km downstream from the dam, thus establishing itself within the limits of the typical uncertainties associated with dam break studies. Thus, the potential of using this type of approach in previous studies of large dam failures is explored, configuring this method as an alternative to the use of robust or simplified models for determining downstream areas potentially affected by these disasters.

Abstract Wetlands are one of the most productive yet altered ecosystems due to human activities across the world. They rely largely on their water flow to provide several ecosystem functions. Then, to develop a land use plan that allows a productive use maintaining the ecological integrity it is critical to understand the flooding patterns. In that sense, the capability of remote sensors to estimate water cover for large areas at detailed spatial and temporal scales can help to develop managerial decision tools. However, the temporal and spatial variation of water components may alter it spectral properties. We studied the capability of different MODIS derived spectral indices to estimate water cover or water presence-absence. The study region was the Paraná Delta River, which is a 2 Mha wetland area. Between all the models evaluated, one based on the spectral index NDWI1 ((Red – SWIR) / (Red + SWIR)) was the most accurate. A NDWI1 = -0.2 threshold allowed to separate those pixels with less than those with more than 60% of water cover with an accuracy of 91%. By this model, we described the flooding patterns of different landscape units of the region during the last 12 years and classified the region according to the impact of ordinary and extraordinary flooding events. We consider this information can help to improve the knowledge about the hydrodynamics, monitor the impact of some activities and develop a more sustainable regional planning.

Resumen Los humedales están entre los ecosistemas más productivos y, a su vez, están fuertemente alterados por el ser humano. Los múltiples servicios que proveen dependen en gran medida del flujo de agua. Por ello, para desarrollar un plan de uso de la tierra que permita un uso productivo manteniendo la integridad ecológica es fundamental comprender los patrones de inundación. En ese sentido, la capacidad de los sensores remotos de estimar la cobertura de agua en áreas grandes a escalas espaciales y temporales detalladas contribuirían a desarrollar herramientas que favorezcan la toma de decisiones. Sin embargo, la variación temporal y espacial de los componentes del agua puede alterar sus propiedades espectrales. Se estudió la capacidad de diferentes índices espectrales derivados del sensor MODIS para estimar la cobertura de agua o la presencia/ausencia de agua. La región de estudio fue el Delta del Río Paraná, un humedal de 2 millones de hectáreas. Entre todos los modelos evaluados, uno basado en el índice espectral NDWI1 ((Rojo - SWIR) / (Rojo + SWIR)) fue el más preciso. Un valor umbral de NDWI1 = -0,2 permitió separar píxeles con menos de 60% de cobertura de agua de aquellos con más del 60% con una precisión del 91%. Mediante este modelo se describieron los patrones de inundación de diferentes unidades de paisaje de la región durante los últimos 12 años y se clasificó la región de acuerdo al impacto de los eventos de inundación ordinarios y extraordinarios. Consideramos que esta información puede ayudar a mejorar el conocimiento sobre la hidrodinámica, monitorear el impacto de algunas actividades y desarrollar una planificación regional más sostenible.

ABSTRACT Alteration of a natural ecosystem can physically, chemically and biologically affect a determined area. Therefore, this study aimed to evaluate the relation between the hydrology, soils and vegetation existing in an area changed by the implantation of a Hydroeletric Power Plant (HPP) in the municipality of Roque Gonzales, Rio Grande do Sul state. The study area was composed of three samples located downstream of the dam. This analysis was performed by the points method to verify the existence of similarity patterns between the vegetation, inundation levels and edaphic soil characteristics of each sample. As a result, greater floristic similarity was observed between the species as a relation of the spatial location with inundation levels. Thus, we can conclude that the vegetal establishment in the study area is under the direct influence of waterflow variation levels from the HPP, which contributes to defining species adaptability to these specific conditions, among others.