Volume XXI |

Ecosystem behavior face to climatic changes and anthropogenic actions. Case study: a north-eastern urban wetland, Tunisia

Abstract: Wetlands environments are ecosystems threatened by climate change and urban sprawl. Studying the behavior of Sabkhaof Sousse, the green lung of the industrial region of Sidi Abd Elhamid in north-eastern Tunisia, is necessary to improve the living conditions of the population living within this ecosystem. This study analysis the impact of climate change and human activities on the seasonal and pluriannual behavior of this Sabkha by using multitemporal series of high-resolution satellite imagery, and a survey among the inhabitants of the area. Shorelines from 2003 to 2019 were vectorized in GIS environment using georeferenced images from Google Earth platform. Then, Land Use Land Cover changes were detected by using Environment Visualizing Imageries software. Results show that built-up and cultivated areas have increased by 4.3 % and 18.5 % respectively in the North and East side of the study area. Moreover, climatic changes during the seasons lead to changes in the soil occupation. Hence the importance of setting up strategies to preserve this brittle ecosystem. The development of an urban park around the Sabkha will enhance the local population’s living conditions while also protecting the Sabkha from degradation.

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 XVII |

Arch dam failure preliminary analysis using HEC-RAS and HEC-GEO RAS modeling. Case study Someșul Rece 1 reservoir

Abstract: This paper presents a preliminary analysis/simulation of the Someşul Rece 1 dam breaking scenario, from the homonym hydrographic basin, located in the north-eastern part of the Apuseni Mountains, at a 0.1 % probability tributary flow rate calculation. The study of the floodplain areas, that occur after the failure of the Someşul Rece 1 dam, was achieved with the help of 1D hydrological modelling. This type of modelling is one of the most complex (Cameron et al., 2006), involving both, the definition of a model with temporal evolution of the dam rupture, and the simulation of a unsteady flow stream in the downstream sector. For the dam analysed area and the downstream sector, several scenarios and modelling of hydrological systems was achieved, with the help of HEC-RAS 5.0.3 software, developed by the Hydrologic Engineering Center (U.S. Army Corps of Engineers).This free software is the most widely used worldwide in the domain, particularly by the official agencies, having a continuous development, given by the involvement of specialists. The software simplifies the problem of hydrodynamic modelling, due to the limitation to a 1D model. Because the flood obviously has a spatial character, GIS software (ESRI ArcGis with the HEC-GeoRAS extension) were used in determining and defining the hydrographic elements (channel, talweg, banks etc.) and, also, in the representation of the results. Maps of the flood-prone areas have been developed, maps which indicated the magnitude of the estimated accidental flood downstream. The results of the simulation were also used to determine the anticipation time.

Volume XVI |

Preliminary results in assessing flood-prone areas using UAS System within the Ozana River Upper Basin (the Eastern Carpathians)

Abstract: The UAV technique, and more recently UAS systems, play an ever important role in various domains of research and practical activities. The increase in number of publications focusing on their applicability is spectacular. The objective of this study is to highlight the efficiency of an integrated command-overflight-taking photo system, in an area with obvious problems related to hydric hazards and risks. The quasi-circular shape, the petrography of the upper Ozana basin, its orientation and its opening to the air masses predominantly movement direction, represent just a few of the reasons why it was chosen as the case study. Also, the settlements are displayed on the valleys thread, and this confluence has a remuu potential, in case of isolated rains in the two related subbasins. The UAV Phantom 4 quadcopter, the UAS system, the DroneDeploy application, the UAVPhoto application, the Visual-SFM application, the Daisy algorithm, the micro triangulation network (mesh), the work surface textures, a hyper-resolution of orthophotoplan, DSM model with a 5 cm resolution etc. are the technical elements that made modelling at a very high detail possible. The probability flow rates that were used, were provided by the two hydrometric stations located very close to the study area. Theywere calculated using professional applications approved at the national gauging network level, using the established Krițki-Menkel and Pearson III statistical distributions. The cross-section profiles was performed in the 10.x ArcMap module, using the 3D Analyst extension, and the hydraulic calculation to obtain the average velocity was done using the Manning equation; subsequently, the floodable surfaces was delineated on these profiles. Using the same ESRI module, the flood prone area polygon interpolation and it overlapping over the terrain model and over the orthophotomap were achieved. Paradoxically, the analysis of the results indicates a low degree of the anthropogenic habitat damage, but this aspect is due, in large measure, to the intervention of technical teams in the recalibration of the minor riverbed, massively clogged by alluvial transport.

Volume XV |

Exceptional floods in small basins in North-Western Romania and the induced effects – Bârsău River, Maramureș county

Abstract: The study aims to analyse floods from May 1970, June 1974 and May 2015, which occured in the Bârsău catchment area, one of the right tributaries of the Someș River. The junction between these two rivers is downstream of Satulung locality in Maramureș County. Bârsău catchment area is located between the Someș and Lăpuș catchment areas and has a surface of 152 km2. The floods of the Bârsău River are fast and have a very short propagation time. They are caused both by rainfalls and snow melting. This is the case of the flood from May 1970, which had a duration of two days, whereas the floods from June 1974 and May 2015 occured just because of heavy rainfalls. From the three analyzed floods, the May 2015 flood, with a pluvial origin, reached the maximum level of 220 cm (DL+20 cm) at Buciumi gauging station and its effects strongly affected local people. Thus, the damages in the villages located inside the basin were recorded first, then quantified. After that, there were made the integrating maps of the flood prone areas as well as the hydrological and associated risks in order to identify areas with different degrees of vulnerability.