Volume XXII |

The changing river course and its impact on riverine society: A case study on the Padma River, Murshidabad District, West Bengal (India)

Abstract: River bank erosion within Murshidabad district is a tragedy, which happens haphazardly along the bank of the Padma River system. The main objective of the study is to analyze the changing river course and its impact on society. By comparing the toposheet and Landsat (5 and 8) images of the Padma River of the Murshidabad district from the years 1924, 1990, and 2020, it is clearly observed that there have been significant changes on the southern portion of the river since 1924 (Bhagawangola II, Raninagar II, and Jalangi Block), while less changes occur on the central part of the river, which is near the Lalgola block. But in the year 2020 significant changes have been found in the northern and middle portion of the district near Samserganj and Lalgola block. Those parts belong to a highly vulnerable zone of bank erosion. This study analyzed some factors, such as soil stratification of the river bank and human encroachment as an obstruction to the natural river flow, also responsible for bank failure. The river has been consuming the vast portions of the right bank every year due to its increasing sinuosity. The victims are mostly in the Samserganj, Lalgola, Bhagawangola II, Raninagar II and Jalangi blocks, who suffered greatly from 1924 to 2020 due to moving of river course by 27% on the right side, which is notified from cross sectional analysis. Additionally, the predicted erosional impact of the region highlights the socio-economic perspective of the research area.

Volume XXII |

Flood risk modelling using HEC-RAS and GIS in the semi-urban water-shed of Oued Ziad (Constantine, North-Eastern Algeria)

Abstract: The study of flood risk in Algerian cities has become essential given the multiple issues at stake (urbanization, urban sprawl, easements, infrastructure, soil structure, etc.), which constitute vulnerable elements, as well as their frequen-cy and repetition in time and space. This has become a problem for the city and the urban environment, particularly in large metropolises such as Constantine. The watershed of Oued Ziad located in the northwestern part of the city of Constantine has experienced exceptional flooding, causing loss of life and property in the Jebli Ahmed agglomeration in the Hamma Bouziane township. The main objective of this research is to identify the factors aggravating the risk of flooding in the Oued Ziad watershed, to analyze the frequency of maximum daily rainfall to determine peak flows for different return periods of 10, 20, 50, 100 and 1000 years, and to map the extent of the flood hazard in the Oued Ziad watershed for a centennial flow, using geographic information systems and HecRas software. The simulation results show the overflow of Oued Ziad on national road N°27, affecting a part of the agglomeration located downstream by a centennial peak flow equal to 50. 98 m3/s and a water height exceeding 3 m, which confirms the extent of the area exposed to risk during the flood that occurred on 19/9/2018. The field survey shows that several anthropic factors in-crease the risk of flooding while the capacity of the existing hydraulic structures is insufficient to evacuate water during floods, which requires the development of this watercourse and its banks to protect the population and its property from the risk of flooding and to reduce the impact on the city’s environment and socio-economic activities.

Volume XXI |

Morphometry and Topographic Wetness Index Analysis for flood inundation mapping in Mata Allo watershed (South Sulawesi, Indonesia)

Abstract: Along with climate change, natural disasters will occur more frequently such as floods. Floods that occur in watersheds which include various human activities, such as Mata Allo (Indonesia) will especially cause a large enough impact. The elongated shape of the watershed has a slow response to peak discharge and time lag. The Mata Allo watershed is dominated by slopes above 25%→45% (65%) and agricultural land use which accounts for 53% of the area, which has an obvious impact on the amount of runoff and erosion that occurs. The eroded soil will be carried away by surface runoff and deposited in the plains between mountains and river floodplains. Based on the results of the study, the Topographic Wetness Index (TWI) map indicates that the part between the mountains and the floodplain around the Mata Allo river had a high TWI value. A high TWI value indicates a high vulnerability to anticipate flooding in the event of overflowing from the Mata Allo River. River morphometry, land use, and hydrological behavior in a watershed are closely related to the TWI value in the Mata Allo watershed.

Volume XXI |

Correlation between precipitation and orography – key element of the Spatial Decision Support System for Prevention and Management of Floods in the Firiza Basin (Northwest Romanian Carpathians)

Abstract: Research on the influence of relief on precipitation has been identified in many studies conducted locally, regionally or globally. However, the research on the area analyzed in the present paper is comparatively lacking. The surrounding mountain area we refer to is represented by the Someș and the Tisa watersheds. The present study focuses on analyzing the influence of the relief, i.e. of the altitude, slope orientation relative to the position of the Sun and the movement of air mass as a factor on precipitation and rainfall gradient. For that, datasets of daily precipitation recorded at 62 rainfall stations were used, as follows: 36 rainfall stations in Maramureş County, 19 rainfall stations in Satu Mare County, and 7 rainfall stations in Bistrița-Năsăud County. Precipitation data from rainfall stations located in the neighborhood of the study area were used in order to determine the influence of relief on frontal precipitation. The second purpose of the research was to determine if there is a correlation between precipitation and altitude. To this end, ArcGIS and Microsoft Office software were used. The results seem to confirm the major influence of the relief over the dynamic convection imposed to the air masses on ascending slopes, various average vertical precipitation gradients and differentiated distribution of rainfall. The present analysis and its results will highly contribute as an input element in a Spatial Decision Support System for Prevention and Management of Floods in Firiza Basin (North-Western Carpathians).

Volume XX |

Analysis of the Relationships Between the Phreatic Aquifer and Natura 2000 Habitats from ROSCI0224 Scroviștea

Abstract: The analysis of the relationships between groundwater and terrestrial ecosystems contributes to the conservation of biodiversity and the quantitative and qualitative status of the aquifer.The main goal of the paper is to analyze the relationships between the phreatic aquifer of ROIL16 (Vlăsia Plain) and the six Natura 2000 habitats from the Site of Community Importance (SCI) ROSCI0224 Scroviștea. This work is based on hydrogeological, geological data, mathematical modeling of the phreatic aquifer (October 17-19, 2017), and the methodology used for study the relationship between groundwater bodies and terrestrial ecosystems, developed by the R.A.H. (2015). The evaluation of the dependence (high – A, medium – B, nule – C) relations, between the phreatic aquifer and the habitats, is made mainly by correlating the depth of the hydrostatic level with the depth of the root system of plant and tree species. The main findings based on the hydrogeological, ecological criteria, and analysis algorithms highlight the fact that most habitats and later the Scroviștea site are dependent on groundwater. The six Natura 2000 habitats (3150, 3160, 91M0, 91F0, 91E0 și 92A0) are analyzed individually concerning the depth of the groundwater level. In the evaluation of the degrees of dependence of the habitats, two other criteria are applied, maximum and arithmetic mean about their extension surface. Thus, four habitats (91M0, 91F0, 91E0, and 92A0) are identified with high dependence on groundwater, and two habitats (3150 and 3160) with nule dependence. Considering only this stage of analysis, it was considered that the SCI Scroviștea has a high dependence on the phreatic aquifer.For a correct assessment of the dependence relations between groundwater and habitats, analyzes related to the hydrodynamic and hydrochemical regime of the groundwater aquifer and the correlation of this information with analyzes from specialized studies performed for plant and tree species are required.