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Volume XXIII |

Gully erosion processes and their management in the Trivale Forest Park, Pitești city, Romania

Abstract: The purpose of this study is to analyze gully erosion processes and their management in the Trivale Forest Park. Although the inclusion of gullies in the category of risk phenomena is still debated, due to their spatial extent and evolution, both longitudinally and vertically, they can pose concern to woody vegetation by altering slope stability. This is the case of the Trivale Forest Park, situated in Pitești city, where gully erosion has been affecting tree growth and recreational activities, such as hiking or cycling, which has led to the implementation of erosion control measures and hydrotechnical structures. By carrying out field observations and cartographic analyses, the research has/proposes/seeks to support two objectives: firstly, to establish the impact of erosion processes on the valleys’ and slopes’ balance by evaluating the type of erosion processes and resulting features and secondly, to assess the exposure of the Trivale Forest area to erosional forms, by using GIS and the frequency ratio (FR) techniques. The results of the multicriteria analysis highlighted, in good agreement with the field observations, the areas most susceptible to slope erosion processes.

Volume XXIII |

Mapping desertification susceptibility in the Hodna watershed Algeria, using a remote sensing-based logistic regression approach

Abstract: This study aims to identify regions prone to desertification in the Hodna basin, which covers a vast area of the vulnerable Algerian Steppes. Thirteen factors were selected as independent variables: geomorphological factors (wind and water erosion, Topographic Position Index (TPI), Drainage Density, Slope, Aspect, Elevation), environmental factors (Normalized Difference Vegetation Index (NDVI) and Evapotranspiration), soil factors (Land surface Temperature (LST) and Normalized Difference Salinity Index (NDSI), and socio-economic factors (the Human Influence Index (HII) and the Livestock. Due to the lack of previous desertification data, NDVI anomalies served as the dependent variable. all of the variables were mainly derived using remote sensing techniques and a logistic regression model was applied for analysis in the R environment for desertification susceptibility mapping, displaying stable predictive power with a Receiver Operating Characteristic (ROC) curve of 0.76. Unlike the Northern part of the Mediterranean, where water erosion is predominant, wind erosion and soil salinization emerged as key factors in this study, while the socio-economic factors had less influence than anticipated. The resulting map shows that 45.4% of the basin is highly to very highly susceptible to desertification, provinding essential data for targeted intervention strategies.

Volume XXIII |

Modeling peak discharge on the Siret River (Romania)

Abstract: The purpose of this study is to identify potentially flood-prone areas in the section between the Siret hydrometric station and the confluence of the Siret River with the Suceava River.
Data related to water flow and specific flow parameters were incorporated into a dedicated hydrodynamic modeling program, in accordance with its requirements (DHI). The construction of the model focused on reproducing the field’s reality as faithfully as possible. Flow parameters were individually configured for each calculation section, taking into account their specific characteristics. Roughness values were determined non-uniformly based on the areas traversed by each cross-sectional profile.
Great emphasis was placed on model calibration, using monitored data from the Zvoriștea and Huțani hydrometric stations as reference points. A time series spanning 15 years, including two of the largest floods recorded in the sector, was used. Following the simulation of two scenarios, Q1% and Q0.1%, three types of files were generated, describing the flood boundary, water depth at each point on the boundary surface and water velocity at each point within the flood boundary. Localities and types of potentially flood-prone surfaces were identified on a map using GIS techniques. Furthermore, flood boundary limits from different scenarios were overlaid to quantify areas at risk of flooding. Although the scenarios were simulated on a previously calibrated model, the fact that the simulated flows exceeded the observed flows required several post-calibration steps. In the case of the first scenario, the simulation did not show significant errors, precisely because the Q1% flow is close in value to the maximum flows observed during the calibration period. In the case of the second scenario, the fact that the flow extended to non-specific areas even during historical maximum flows, resulted in stability errors or non-conforming results obtained by the program, inconsistent with research and studies in the field.

Volume XXIII |

Simulation of flood hazard in the semi-urban and urban using GIS and HEC-RAS of Wadi Nagues (Tebessa, North-Eastern Algeria)

Abstract: Floods are considered one of the most significant natural threats to cities and their infrastructure, especially when urban resilience is weak of floods, due to both human and natural factors. This is the case in the Algerian city of Tebessa, where urban resilience is low in the watershed of Wadi Nagues, which divides the city from north to south. Informal expansion along the riverbanks and inadequate city infrastructure increases the risk of flooding in the city. This study aims to identify the factors that increase flood hazards in Wadi Nagues and analyze maximum daily rainfall values to determine the maximum flood flow and volume during different return periods of 10, 50, 100, and 200 years, in order to map the floodplain of the river. This is accomplished using Geographic Information Systems (GIS) and HEC-RAS software for flood simulation. The results of the flood simulation in Wadi Nagues show that river waters inundate the southern areas of informal expansion, the airport, the railway, Houari Boumediene neighborhoods, and the Constantine Road – which is an economic artery for the city. The peak flow reaches 86.82 m³/h, and the volume of flow is 159.20 m³/s, in a during a 200-year return period. Field surveys also reveal several other human factors that increase the risk of flooding, such as informal expansion, lack and weakness of flood protection hydraulic structures, and poor river water cleanliness. This necessitates intervention to protect the city from flood hazard.

Volume XXIII |

Analysis of the seasonal and spatial variation of surface water quality parameters in Enugu Urban Rivers, Southeast, Nigeria

Abstract: Seasonal quality assessment of surface water provides not only a better understanding about pollution dynamics in water bodies but also information for the implementation of sustainable water-use management strategies. Such vital information is lacking for surface waters in most cities in sub-Sahara Africa region, especially Nigeria. The study aimed, therefore, to examine the seasonal physio-chemical characteristics of surface waters in Enugu urban, southeast Nigeria, during the dry and wet seasons. Twelve Surface water samples were collected from the six major rivers in Enugu urban during two seasons (wet and dry seasons). Their physico-chemical characteristics were determined by specific analyses between 2020 and 2022. Some of the parameters were measured in situ whereas bacterial analysis were analysed in the laboratory. Seasonal fluctuations in surface water quality characteristics were determined and the pollution status was compared to WHO standards. The results revealed that the parameters like Turbidity, Ammonia, Nitrate, Nitrogen, Fecal coliform and total coliform were above the WHO permissible limit at all sites and for all seasons. Various anthropogenic activities, untreated sewage and effluent were the major sources of pollution to the river ecology and the surface water. Overall monitoring network results must be used to control pollution in catchments where industrial and urban activities are increasing in other to ensure effective water quality management, sustainability and safety.