fg

Subscribe2


 

Volume XV |

Shape characteristics of fluvial islets based on GIS techniques. A case study: the Danube’s islets between Giurgiu and Olteniţa

Abstract: This study aims to quantitatively characterize shape parameters of fluvial islets using GIS techniques. There were eight metrics selected for the analysis. For the automation of the workflow, all processing functions were joined into a single graphical model. For this case study we selected the Danube sector situated between the cities Giurgiu and Oltenita. We chose to track the evolution of the fluvial islets’ shapes from 1864 to 2010. Information was extracted from historical data sources such as maps and ortophotoplans. The graphical model created was run for each studied year.
The results show major changes in the aspect of fluvial islets along the Danube reach. Between 1864 and 2010 the number of islets slightly increased with the total area ranging from 21.19 kmp to 27.96 kmp. In the period studied, the shape turned from a rounded aspect to a more elongated one. Knowledge of the information on the shape of those landforms is relevant for river restoration strategies, nature conservations of islets and maintenance of the protected habitats.

Volume XIV |

The North Atlantic Oscillation Influence on the Climate and Flow Variability of the Lower Danube Valley, between the Towns of Olteniţa and Călărăşi, Romania

Abstract: As previous international research has identified, the large-scale NAO atmospheric circulation pattern dominates climate variability in the northern hemisphere. In this study we investigate the impact of the North Atlantic Oscillation (NAO) index on annual/winter precipitation and river flow regimes for a sector of the lower Danube Valley. An important goal was to test the relation between the NAO pattern and the occurrences of extreme events. We assume that precipitation variability and river flow are harder to assimilate into a modified anthropogenic environment as the situation of the Danube in the study area. During the communist regime, this valley sector was transformed from a wetland environment into a farming area.
Understanding NAO – rainfall and NAO – river flow relationships were based on monthly data in the time period between January 1977 and December 2010 for the NAO index, the river basin average precipitation over the Danube and the Danube river flow measured at Oltenita and at Calarasi Stations. Results showed that the large inter-annual variability in the precipitation regime and flows of the Danube is largely modulated by the NAO phenomenon. The four-time series in study are weak stationary, which means that the natural events vary moderately along a constant mean and the extreme events do not have the power to propagate, vanishing after few time steps.

Volume XIV |

Seismic loss estimates for buildings in Bucharest’s historic centre in case of another 1977 Vrancea earthquake

Abstract: As past seismic events showed, Bucharest (capital of Romania) can be significantly affected by another intermediate depth (or subcrustal) Vrancea earthquake. The 1940 (Mw 7.7) and 1977 (Mw 7.4) earthquakes put the number of casualties in Bucharest over 1600. Although most people and authorities are aware of the exposure, the mitigation actions are still improper and there is actually a very uncertain image of the current damage extent. The paper provides scientifically based answers, through quantitative earthquake loss estimation based on recently developed analytical methods, applied for buildings in the historic centre of Bucharest. The approach offers a relevant picture of the actual possible damage distribution after an earthquake similar to the 1977 event, in an area with heavy traffic and a high number of tourists. The Improved Displacement Coefficient Method used in this study relies on the description of structural behaviour within different limits due to specific ground motion parameters like spectral acceleration. The 358 buildings in the study area are assessed individually and specific vulnerability curves are assigned to each typology, based on height, construction year and material. The same classification as in the Near Real-Time System for Estimating the Seismic Damage in Romania is used. The results are evaluated in order to be further included in the system. In addition, an empirical loss assessment procedure reflecting the economic impact of the previously calculated situation was employed. Relevant maps for mean damage ratio and economic losses are presented and interpreted.

Volume IX |

The Intensification of Antropic Pressure Through the Expansion of the Constructed Area in the Subcarpathian Sector of the Prahova Valley/Romania (1800-2008)

Abstract: The present research focuses on the evolution of anthropic pressure on the environment through the continuous development of the constructed space, in a diachronic comparative analysis of urban-rural environment, detailed on the basis of two characteristic examples: Breaza town and Cornu town. The information resulted from the historical maps was completed by mapping from the ortophotoplans and GPS land surveys. The data base went through statistic differential processes and correlational analysis with the conditions of the physical support, highly important limitations and favorabilities in the assessment of the vulnerability of the Subcarpathian space being revealed.