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Water ◽  
2022 ◽  
Vol 14 (1) ◽  
pp. 112
Author(s):  
Sérgio Lousada ◽  
Leonardo Gonçalves ◽  
Alper Atmaca

This study aims to examine the flood propensity of the main watercourse of São Vicente drainage basin and, if relevant, to propose two methodologies to alleviate the impacts, i.e., detention basin sizing and riverbed roughness coefficient adjustment. Geomorphological data were obtained from the watershed characterization process and used through the SIG ArcGIS software for the flood propensity assessment and then for the calculation of the expected peak flow rate for a return period of 100 years through the Gumbel Distribution. Subsequently, the drainage capacity of the river mouth was verified using the Manning-Strickler equation, in order to establish whether the river mouth of the watershed has the capacity to drain the entire volume of rainwater in a severe flood event. In summary, it was possible to conclude that São Vicente’s watershed river mouth is not able to completely drain the rain flow for the established return period. Thus, its drainage capacity was guaranteed by modifying the walls and streambed roughness coefficient and by sizing the detention basin using the Dutch and the Simplified Triangular Hydrograph methods.


MAUSAM ◽  
2021 ◽  
Vol 63 (1) ◽  
pp. 65-70
Author(s):  
M.S. TOMAR

In this paper severe flood during South West monsoon seasons of 2005, 2006 & 2007 have been identified with the related synoptic features. A total of 22 states reeled under severe floods during 2005, 2006 & 2007. In the south peninsula only Karnataka and Kerala were affected by severe floods. During 2006 & 2007 severe floods continued for a longer period and affected many states where as during 2005 severe floods affected most of the states except peninsular India but they continued for short periods comparatively.Formation of excess No’s of low pressure areas and depressions in the Bay of Bengal during July, Aug and Sept 2006, in succession , and their WNW movements upto M.P. and east Rajasthan caused severe floods in Gujarat, Maharashtra, Rajasthan, Madhya Pradesh, Chattisgarh, Orissa and Andhra Pradesh for a longer period i.e. from 28 July to 12 September 2006. During 2007, Shifting of monsoon trough, presence of secondary monsoon trough and trough in westerly, caused severe floods in most of the North eastern states from 12 July to 10 October 2007.


Author(s):  
Eisa Ebrahimi ◽  
Hossein Asadi ◽  
Mehrnosh Joudi ◽  
Mehran Rezaei Rashti ◽  
Mohammad Bagher Farhangi ◽  
...  

Abstract Phosphorus (P), nitrogen (N) and organic component are released from the soil into surface bodies by runoff and erosion, causing the pollution and eutrophication of water resources. This study was aimed to investigate the seasonal changes in loads of N and P components, and organic matter (OM) in the Pasikhan River in flood and normal conditions. Sampling was performed monthly during normal flow conditions and for five flood events. The concentrations of P and N components were measured in the samples. The OM of the suspended sediments was determined by the combustion method. Under the normal flows, the maximum loads of total P and OM were about 0.553 mg l−1 (STD = 0.11) (November) and 3.41% (STD = 1.17) (November) in the autumn, respectively. The total N concentration of 0.533 mg l−1 (STD = 0.12) was observed in the winter. In the flood events, the TP, TN and OM ranged from 0.48 to 3.5 mg l−1, 0.28 to 0.79 mg l−1 and 1.24 to 4.11%, respectively. The results indicated a high risk of eutrophication in the Pasikhan River. Also, the study revealed that in a severe flood event, some 113.9 tons h−1 of OM can be released from the river watershed. Furthermore, there was a high correlation between the amount of P and OM losses with the concentration of suspended sediments in different flood events. Finally, it is concluded that if the floods are not controlled, they not only cause a rapid loss of soil nutrients and OM but also lead to severe eutrophication in the Anzali wetland.


Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1549
Author(s):  
Chiara Biscarini ◽  
Silvia Di Francesco ◽  
Stefano Casadei ◽  
Sara Venturi ◽  
Piergiorgio Manciola

The conditions of high hydraulic risk are mainly due to the interference between the river network and bridges, their relative access ramps and road embankments located in the floodplain. Actually, bridges are not always structurally adequate to withstand severe flood waves. In flood restoration works, there is an objective difficulty in implementing the structural safety of bridges because of historical, artistic and economic issues. Thus, the risk mitigation strategy often accounts for the assessment of the vulnerability degree of each bridge/road embankment according to an evaluation scale. Here we present a methodology regarding the classification of the vulnerability degree and its application to 84 works located in the alluvial area of the Tiber River, in the area of the Province of Perugia. For the purposes of a synthetic classification of works vulnerability, the individual assessed parameters are compared by means of subsequent contingency tables in order to compute the resulting vulnerability degree.


2021 ◽  
Vol 8 (2) ◽  
pp. 1-16
Author(s):  
Mohit Prakash Mohanty ◽  
Subhankar Karmakar

A serious constraint of data availability over flood-prone areas in India limits the potential of carrying out hydrodynamic flood modelling studies. Such difficulties are encountered because of a lack of high-resolution topography, cross-section data of the rivers, and sufficient and accurate calibration and validation data sets. The present study addresses the problems faced in performing a comprehensive 1D-2D coupled flood modelling over a flood disastrous region Jagatsinghpur, Odisha, India. The constraints faced in terms of hydraulic parameters such as water level, discharge, and geometric parameters such as river geometry are investigated. The simulations were performed for a severe flood event in 2011 that incurred heavy socio-economic losses in the district. The establishment of a modelling platform for flood simulation shall elucidate the major constraints faced in hydrodynamic modelling for such flood-prone areas with poor data availability.


2021 ◽  
Author(s):  
Tobias Pilz

<p>The megacity of Lagos, Nigeria, is subject to recurrent severe flood events as a consequence of extreme rainfall. In addition, climate change might exacerbate this problem by increasing rainfall intensities. To study the hazard of pluvial flooding in urban areas, several complex hydraulic models exist with a high demand in terms of required input data, manual preprocessing, and computational power. However, for many regions in the world only insufficient local information is available. Moreover, the complexity of model setup prevents reproducible model initialisation and application. This conference contribution addresses these issues by an example application of the complex hydrodynamic model TELEMAC-2D for the city of Lagos. The complex initialisation procedure is simplified by the new package ‘telemac’ for the statistical environment R. A workflow will be presented that illustrates the functionality of the package and the use of publicly available information, such as free DEMs and Openstreetmap data to cope with the problem of insufficient local information. By further analysis and visualisation procedures along the workflow the increasing hazard of pluvial flooding for Lagos is shown. The workflow makes model initialisation, application, and the analysis of results reproducible and applicable to other regions with a relatively low need for manual user interventions and without additional software other than R and TELEMAC-2D.</p>


2021 ◽  
Author(s):  
Maurizio Mazzoleni ◽  
Johanna Mård ◽  
Maria Rusca ◽  
Vincent Odongo ◽  
Sara Lindersson ◽  
...  

<p>This study aims at exploring whether changes in the spatial distribution of the human population and the built-up areas within floodplains can be associated with extreme flood events generating severe economic losses and fatalities. We relate economic losses and fatalities caused by floods during 1990‐2000, with changes in human population and built‐up areas in floodplains during 2000‐2015 by exploiting global archives as the Global Human Settlement, GFPLAIN250m, and the EM-DAT datasets. Despite the frequent flood losses in the previous period 1990‐2000, we found that population and built‐up areas in floodplains increased in the period 2000‐2015 for the majority of the analyzed countries. On the other hand, we observed a reduction in floodplains population after more severe flood losses that occurred in the period 1975‐2000. Finally, floodplains population increased after a period of high flood fatalities in low‐income countries, while built‐up areas increased after a period of frequent economic losses in upper‐middle and high‐income countries. This study can be used as a general framework for advancing knowledge of human‐flood interactions and support the development of sustainable policies and measures for flood risk management and disaster risk reduction.</p>


2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Hiroshi Matsuyama ◽  
Hitoshi Saito ◽  
Valerii Zemtsov

AbstractSoil Water Index (SWI) represents the conceptual water stored in the soil and is calculated using a three-layer tank model with hourly precipitation. In Japan, landslide disasters are likely to occur when SWI in an event exceeds the maximum value of the past 10 years; however, snowmelt-driven landslide disasters have not been considered yet. Using the tank model that simultaneously calculates SWI and runoff, we implemented the snowfall-accumulation-snowmelt processes into the original SWI and applied the modified SWI to meteorological data in Tomsk, Russia, in spring 2010 when severe flood and landslide disasters had occurred. We conducted a sensitivity analysis of hourly precipitation in snowy region in Japan considering that meteorological data in Russia are available every 3 h. When we input the average of the three-hourly accumulated precipitation to calculate SWI, the result was almost identical to that of the observed hourly precipitation being given. We then estimated the hourly temperature by linearly interpolating the data every 3 h, and set the threshold of liquid/solid precipitation. The degree-hour method was employed to calculate the snowmelt. The modified SWI predicted the occurrence of snowmelt-driven landslide disasters in Japan when the calculated SWI exceeded the maximum value in the snowmelt season (March–May) for the past 10 years. When applied to meteorological data in Tomsk, the modified SWI and calculated runoff captured the timing of snowmelt-driven flood and landslide disasters in spring 2010. We demonstrated that by focusing on the maximum value of SWI in the snowmelt season for the past 10 years, we can predict snowmelt-driven landslide disasters.


2021 ◽  
Author(s):  
Zhengrong Xu ◽  
Yuda Yang ◽  
Tao Sun

Abstract Social adaptations to natural hazards have been influenced by various social and economic factors including traditional cultures such as Feng Shui that is known as Chinese geomancy. This study examined not only the progressive processes and spatial distribution of the 1849 severe flood in Nanjing city but also subsequent countermeasures based on historical documents, maps, and digital elevation model (DEM) data. As an adaptation to extreme floods, a project that connects Xuanwu Lake to the Yangtze River has been deeply discussed to relieve the flood risk. As the role of the traditional concept of Feng Shui in China was not neglectable, however, local officials and elites of Nanjing city worried that the project may destroy the Feng Shui of the city, which may bring misfortune to local candidates in the Imperial Examinations, their future promotion, and the prosperity of their families. This indicates that, in the complicated traditional Chinese society, such traditional cultures may play an important role in determining social adaptations to climate change. However, these concepts may not lead to a consensus without specific institutional culture. Hence, in a complicated traditional society, the institutional culture was also fundamental to build social adaptations to climate change. This project has been eventually completed in 1931 as the concepts have kept dynamically being changed in a complicated society, which demonstrates that the relationship between the culture and the social adaptation to climate change is also evolving.


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