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A biological invasion is a form of biological pollution that is most likely more terrible than chemical pollution. Xanthium spinosum is one of the most invasive alien plant species. However, its abundance and impacts on invaded plant communities have not yet thoroughly studied. This study aimed to investigate the abundance and impacts of X. spinosum on invaded plant communities in the North Shewa Zone, Ethiopia. The study applied the quadrat method, sampling 80 main plots within 1 m2. Differences in mean cover-abundances of X. spinosum across various land types were compared using one-way-ANOVA followed by Tukey’s Honestly Significant Difference (HSD) Test. The results showed that roadsides and flooded areas exhibited the maximum mean cover-abundance of X. spinosum compared to farmland and rangeland. The number of plant species recorded was 106 in the control areas, compared to only 73 in the invaded areas. Hence, the number of plant species decreased by 31.13% in the infested area compared to the control. Thus, X. spinosum was among the factors contributing to the reduction of plant diversity, affecting the sustainability of biodiversity in the study areas. Therefore, implementing management measures against the spread of X. spinosum is to address the ongoing threat to biodiversity. [ABSTRACT FROM AUTHOR]

A biological invasion is a form of biological pollution that is most likely more terrible than chemical pollution. Xanthium spinosum is one of the most invasive alien plant species. However, its abundance and impacts on invaded plant communities have not yet thoroughly studied. This study aimed to investigate the abundance and impacts of X. spinosum on invaded plant communities in the North Shewa Zone, Ethiopia. The study applied the quadrat method, sampling 80 main plots within 1 m2. Differences in mean cover-abundances of X. spinosum across various land types were compared using one-way-ANOVA followed by Tukey’s Honestly Significant Difference (HSD) Test. The results showed that roadsides and flooded areas exhibited the maximum mean cover-abundance of X. spinosum compared to farmland and rangeland. The number of plant species recorded was 106 in the control areas, compared to only 73 in the invaded areas. Hence, the number of plant species decreased by 31.13% in the infested area compared to the control. Thus, X. spinosum was among the factors contributing to the reduction of plant diversity, affecting the sustainability of biodiversity in the study areas. Therefore, implementing management measures against the spread of X. spinosum is to address the ongoing threat to biodiversity.

Floods are the most frequent and devastating natural hazard event in Bosnia and Herzegovina. The detected increase in extreme precipitation over the study area in the last period has altered flood event patterns due to climate changes. Higher frequency of flood events and lack of flood protection infrastructure has a severe impact on socio-economic sectors and natural ecosystems. This paper focuses on the identification of flooded areas for each single flooding event in the lower part of the Sana river basin during the period 2016-2020. For delineating flooded areas, both radar and optical satellite imagery were used. Data obtained after processing remote sensing images were overlaid with a detailed land cover map in order to get insight into flooded land cover types. From temporal aspects, floods are most common during the spring season. They are usually caused by rapid snowmelt and prolonged excessive precipitation. Considering spatial aspects, flooded areas vary from 110 to 522 hectares in the study area. Over 95% of the flooded areas are arable land, meadows and pastures. Most affected settlements by floods are urban and suburban area of Prijedor, Gomjenica, Hambarine, Rakovčani, Rizvanovići, Brezičani, Donja Dragotinja, Vitasavci, Svodna, Blagaj Rijeka and urban area of Novi Grad. The applied methodological approach represents a starting point for further investigation of flooded areas in the Sana basin and data obtained by this analysis can be used in water management, spatial planning and emergency planning.

The Tulcea municipality is frequently exposed to rainfall-generated floods, with its lower downtown area (located in the Danube' former meadow, now protected by dikes) being flooded two to three times per year. In this study, our objective was to understand the generation mechanism of these rainfall-triggered urban floods and to identify tailored mitigation options. Due to the lack of reliable information on the sewage network (diameters, slope, material) and the uncertain sewage outflows during heavy rain events, a rather simplified approach was preferred by the authors of this paper. The data processing was performed using GIS tools, with appropriate accounting of the digital terrain modelling, ortho-photos, administrative boundaries of the Tulcea municipality, delineation of the urban catchments, imagery of the frequently flooded areas, and the urban sewage network. Subsequently, a fast hydrological modelling and a volume-based flooding approach were developed in order to identify and evaluate the flooded urban areas under extreme rainfall events. Upon the completion of the calibration and validation processes, numerical simulations were run that considered the design storms of different return periods. Due to the high slopes of the hills, hence the short concentration time of the pluvial waters, a Sponge City approach does not seem as though it would be easy to implement. A more efficient solution utilising large-capacity buried urban retention tanks in the lower part of the municipality was alternatively identified. Further on, this solution will be supported by a set of green measures. [ABSTRACT FROM AUTHOR]

The dry lowlands of Ethiopia are seasonally affected by long periods of low rainfall and, coinciding with rainfall in the Amhara highlands, flood waters which flow onto the lowlands resulting in damage to landscapes and settlements. In an attempt to convert water from storm generated floods into productive use, this study proposes a methodology using remote sensing data and geographical information system tools to identify potential sites where flood spreading weirs may be installed and farming systems developed which produce food and fodder for poor rural communities. First, land use land cover maps for the study area were developed using Landsat-8 and MODIS temporal data. Sentinel-1 data at 10 and 20 m resolution on a 12-day basis were then used to determine flood prone areas. Slope and drainage maps were derived from Shuttle RADAR Topography Mission Digital Elevation Model at 90 m spatial resolution. Accuracy assessment using ground survey data showed that overall accuracies (correctness) of the land use/land cover classes were 86% with kappa 0.82. Coinciding with rainfall in the uplands, March and April are the months with flood events in the short growing season (belg) and June, July and August have flood events during the major (meher) season. In the Afar region, there is potentially >0.55 m ha land available for development using seasonal flood waters from belg or meher seasons. During the 4 years of monitoring (2015–2018), a minimum of 142,000 and 172,000 ha of land were flooded in the belg and meher seasons, respectively. The dominant flooded areas were found in slope classes of <2% with spatial coverage varying across the districts. We concluded that Afar has a huge potential for flood-based technology implementation and recommend further investigation into the investments needed to support new socio-economic opportunities and implications for the local agro-pastoral communities. [ABSTRACT FROM AUTHOR]

Abstract Many factors can influence the structures and distributions of plant communities. Plant diversity of swamp forests reflect responses to water stress conditions. We evaluated the floristic diversity, structure, and composition of the regenerating shrub-tree species of six swamp forests in veredas ecosystems (northern Minas Gerais, Brazil), and the floristic similarities between them. All individuals ≥ 1 cm in diameter at ground level and < 3 cm in diameter at breast height were sampled in one hundred 25 m2 plots in each area. A total of 5442 individuals were recorded, distributed among 134 species, 85 genera, and 47 botanical families, with a diversity (Shannon) of 3.38 and equability (Pielou) of 0.69. Beta diversity was high, while similarities between the areas were low, with only two species common to all six sites. The forests showed different compositions, diversities, and natural regeneration structures, reflecting their ecotone nature and past anthropic impacts.

The Tulcea municipality is frequently exposed to rainfall-generated floods, with its lower downtown area (located in the Danube’ former meadow, now protected by dikes) being flooded two to three times per year. In this study, our objective was to understand the generation mechanism of these rainfall-triggered urban floods and to identify tailored mitigation options. Due to the lack of reliable information on the sewage network (diameters, slope, material) and the uncertain sewage outflows during heavy rain events, a rather simplified approach was preferred by the authors of this paper. The data processing was performed using GIS tools, with appropriate accounting of the digital terrain modelling, ortho-photos, administrative boundaries of the Tulcea municipality, delineation of the urban catchments, imagery of the frequently flooded areas, and the urban sewage network. Subsequently, a fast hydrological modelling and a volume-based flooding approach were developed in order to identify and evaluate the flooded urban areas under extreme rainfall events. Upon the completion of the calibration and validation processes, numerical simulations were run that considered the design storms of different return periods. Due to the high slopes of the hills, hence the short concentration time of the pluvial waters, a Sponge City approach does not seem as though it would be easy to implement. A more efficient solution utilising large-capacity buried urban retention tanks in the lower part of the municipality was alternatively identified. Further on, this solution will be supported by a set of green measures.

Association of lowland reservoirs with marsh systems at an ordinary water level amplitude of 3–5 m can increase the total flooding area 1.5–2 times. The use of remote sensing and GIS for the processing and storage of satellite and field data allows the study and monitoring of wetland ecosystems at a new information and cartographic level, as well as correcting and supplementing existing literary and cartographic data. In this work we used ERS data obtained from the modern Landsat­8 and Sentinel­2 satellites. The GIS­based analysis of changes in the studied landscapes revealed the zone of direct influence of the reservoir inland up to 3.5 km, and allowed the areas of shallow water and adjacent wetland ecosystems to be evaluated and four hydrological zones to be established.

We address a problem of the joint processing of digital maps of the earth surface and satellite imagery of flooded areas as part of the software intended to help authorities to respond to emergency situations. The problem of mapping flooded areas is solved based on the use of satellite images and GIS technologies. This paper describes an algorithm for mapping areas submerged by flooded rivers based on radar satellite images and analysis of characteristic relief features, allowing one to improve the accuracy of the image geolocation with a small number of reference points. The experimental studies demonstrate that using the algorithm proposed, the alignment accuracy of the river water surface obtained from a satellite image and from a digital topographic map has increased by 40%.

In the specialized literature, there are different ways to calculate and display flooded areas by geographical entities (rivers or streams), using mathematical and physical models in 1D and 2D areas; also, the use of tools such as Geographic Information Systems (GIS), the diffuse logic, the neural networks, and the genetic algorithms, among others, has been reported. This article describes the use of Geo-inspired Natural Vectors Agents (AVNG). The AVNG is founded on the agent concept, by integrating the GIS vector model to achieve the construction of an element capable of dynamically representing a geographical entity (vector) from two behaviors: the natural and the induced (Natural Agent); thus, generating an approximation to environmental management. In order to implement the AVNG conceptual model, we studied the Colombian Amazon foothills, where flash floods in urban areas cause material disasters and loss of human lives.

Corrientes City is limited by natural features that prevent its expansion towards the north and west; while toward the south and east, the landscape is seriously affected by periodical floods owing to the presence of “bañados” and “cañadas”. The Lomada Norte is an excellent growing area and constitutes a “source of attraction” to buildings policyspeculation that is manifested in the great demand of occupation of such space. This sandy landscape is characterized by the presence of shallow lakes, which are mostly small, with small depth and with scarce water retention capacity. In this sense, our objective is to demonstrate the impact of the boundaries expansion of the city on the existence and permanence of the shallow lakes near Corrientes city. Thus, aiming to detect changes in the cover of the terrain and their impact on the landscape, satellite images, which allow the analysis of recent changes and, aerial photographs of Corrientes city took in 1950, were analyzed and compared by using GIS methods. The results obtained revealed that, from 1950 to date, 51 shallow lakes have disappeared as a consequence of the spatial expansion of the city, exclusively. Moreover, the analysis of the satellite images also showed that, after a long dried period, the areas previously occupied by shallow lakes were occupied by human settles. It is concluded that the occupation of new areas impact directly on the landscape, being of fundamental importance to implement land development policies to regulate and control the advance of the city frontier, particularly when vulnerable landscapes are affected exposing population to certain risks.

Hydropower is oldest available source for renewable energy generation in Lithuania and the world. However, because of unequal demand of electricity during the day large hydropower plants are adapted to work in hydropeaking regime, which causes rapid water level and discharge fluctuations and has impact on the environment. To assess the extent of this impact in this study 2D numerical hydrodynamic modelling was carried out to reveal the dewatered or flooded stream channel areas at the Nemunas River downstream Kaunas Hydropower Plant. Such estimation of dewatered or flooded areas, considering different operating modes of hydropower plant, was carried out for the first time in Lithuania. It was revealed that largest areas are flooded when Kaunas hydropower plant starts its operation with two and four turbines and accordingly are dewatered when the plant stops such operations. During this study the impact of water level and discharge fluctuations on river ecosystems was not analysed, however the obtained results will be the initial data for more detailed assessment of fish habitats quality under impact of hydropeaking. [ABSTRACT FROM AUTHOR]

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During medium and high intensity storm events, urban drainage networks can rapidly reach their maximum capacity, and subsequently floods can occur. Owing to the non-linearity of the processes involved, it is evident that the return period of a rainfall is different from the return period of the generated overflows. Therefore, the assessment of the maximum overflow volume related to a given return period is a key element in the management of urban drainage networks, since it may cause problems to infrastructure and economic losses. In this paper, a combined methodology for the hydraulic rehabilitation of such networks is proposed, by expressing their hydraulic critical conditions in terms of overflow volumes rather than rainfall volumes and considering both observed rainfall data and synthetic hyetographs derived from statistical analysis. The first application of the proposed methodology to the sewer network of the Mesola Municipality is presented and commented on. [ABSTRACT FROM AUTHOR]

Qualitative and quantitative structures of benthic macro-invertebrates, macrophytes, zooplankton, as well as ichthyofauna and fish parasites of the shallow areas of Small Sevan that flooded as a result of an increase in the lake's water level are analyzed. It is shown that the most appropriate conditions for the development of hydrobionts were found in the area that was flooded earlier and is directly connected with the lake. In contrast, the worst conditions occurred in the area that was flooded later and is minimally connected with the lake. [ABSTRACT FROM AUTHOR]

Campos de murundus (CM) is a savanna vegetation type of Cerrado which remain flooded in the rainy season. It is considered protected areas in the state of Goiás, Brazil, but are under strong pressure due to the construction of drainage ditches around them. In this study we compared sampled and estimated species richness, structure and vegetation dynamics between drained and non-drained areas in CM over a seven-year period. We delimited 10 20x50 m plots in drained areas and 10 plots in non-drained areas with 200 m between them. Friedman's test was used to compare richness and individuals per plot between drained and non-drained areas. A MANOVA was used to compare horizontal structure parameters such as density, frequency, dominance, importance value index, importance value cover, mortality, recruitment, net changes and turnover in individuals and basal area per plot between areas. The estimated richness was higher in non-drained than in drained areas. Density and absolute dominance were greater in drained than non-drained areas. The increase in species richness, individual number, densification, dominance, and recruitment of individuals indicates encroachment of woody plants in the mound fields over time in both areas. Our study suggests a shift on structure of woody layer in CM which may affect ecosystem services such as water circulation in the long term. [Display omitted] • The impact of drainage ditches on Campos de murundus were addressed over 7 years. • The shrubs-trees species were compared between drained and non-drained areas. • The sampled species richness increases in both areas. • The estimated species richness, density and absolute dominance differ between areas. • Animal-dispersed species absolute dominance increases mainly in the drained areas. [ABSTRACT FROM AUTHOR]

A hydrologic-hydrodynamic model of the Yi River basins in Uruguay has been developed as a support tool to the Emergency Coordination Centre of Durazno city. The purpose was to improve the existing decision support system and the emergency planning by providing information on gauge height and its permanence in time, and the risk of flooded areas. Four past flood events of high return period were used for calibration and validation with accurate results. The input data to the operational model in real time are hourly observed rainfall and gauge height, as well as rainfall forecasts by several international sources. The use of predictions from numerical weather forecasts allows for the generation of pre-alert scenarios with larger lead time. These scenarios can warn the emergency coordinators, and thus are of great value to premanage a probable emergency. Operation of a meteorological weather alert issued by the National Meteorological Board is discussed. [ABSTRACT FROM AUTHOR]