Volume XVIII |

How much open water do waterbirds have in the Banat Plain? The first permanent inland water bodies inventory at 10-m resolution using Sentinel-2 imagery at regional – scale

Abstract: In the Banat Plain were recorded more than half of the number of bird species in Romania. There are eleven Nature 2000 Bird Protection Sites (SPAs) and in all of them have been registered aquatic bird species. The water surface areas were greatly reduced since the starting of the hydro-technical works 300 years ago. Nowadays, the anthropic pressure associated with the more frequent drought periods continues to threaten the water bodies, on whose existence the numerous aquatic birds depend. For the mapping and evaluation of open water surfaces in the Banat Plain, in the context of a lack of precise, consistent maps and data, the first water bodies inventory at 10-m resolution was made based on Sentinel-2 multispectral satellite images. The heterogeneous and fragmented landscape, with a great diversity of aquatic units, conducted us to develop an object-oriented approach, which allowed a multi-scale classification process. Both spectral bands and normalized differentiation water indices were used in the rule-based classification algorithm for water detection. The accuracy assessment indicated a very good overall accuracy of 96%, with a Kappa coefficient of 0.91. Also in our dataset, the small water bodies were mapped more accurately than in the other six water bodies datasets at global or European scale we compared with. The results drawn from both qualitative and quantitative assessments indicated that the water dataset developed in this study could be used as an inventory and a reference map for the permanent open water areas from the Banat Plain. It may represent the starting point for better aquatic management and elaboration of ecological strategies to support bird necessities and to counteract the increasing vulnerability and environmental threatening of waterbird species.

Volume XV |

The Assessment of Artificial Water Surfaces Regeneration in Stachinez Swamps Protected Area by Using Remote Sensing and In–situ Data

Abstract: The Satchinez Swamps, a remnant of the swamps once specific for Banat Plain, is an ornithological reserve since 1942 and the habitat of many protected bird species. Draining works conducted in the seventies affected the reserve by decreasing the water surface area. Thirty-five years later, hydro-technical works aiming to restore the former aquatic surfaces within the buffer zone were conducted. Thus, in 2005 a water delivery canal from the discharge canal of Satchinez reservoir towards Balta Mare was built. The objective of this study is to assess the efficiency of the hydrological works carried out in 2005 by using temporal analysis of some normalized difference indexes derived from satellite images, in relation to precipitation data (recorded at Timisoara meteorological station) as an indicator for wetland restoration. We used geospatial data from different time periods: historical maps (1953, 1962 and 1984), orthophotos (1963, 1970, 2005 and 2012), oblique airphotos (2004) and 38 Landsat satellite scenes (1984-2015), two images per year, for the dry season respectively for the rainy season. We noticed a slight increase of the Normalized Difference Vegetation Index (NDVI) in Balta Mare and on the relict watercourse of Sicsău stream, which shows the expansion of reed and suggests an increase in soil moisture. During the dry season, for the period before the restoration works (1984 – 2004) there is a strong, very significant correlation between Normalized Difference Water Index (NDWI) and precipitations (r =0.7008, p = 0.0011). After 2005, this correlation no longer occurs (r = -0.1083, p <0.05), which demonstrates that precipitations are not the main water supply for Balta Mare anymore. For the 1984 – 2015 period, during rainy months the Modified Normalized Difference Water Index (MNDWI) indicate the presence of water in Balta Mare, but during the dry months, it demonstrates the lack of water which underlines the temporary character of this pond and confirms the field observations. We conclude that the restoration did not succeed in the rebuilding of the former water surfaces of Balta Mare, but has an effect in increasing the underground water level in this area followed by reed extension.

Volume XIV |

Snow avalanche tracks mapping within Bâlea glacial valley (the Făgăraș Mountains) using semi-automated detection methods

Abstract: Mapping of snow avalanche tracks based on topographic maps, aerophotos and field data to achieve inventories for the whole mountaineous areas in Romania is an important step in snow avalanche risk assessment and other related geomorphic processes. This requires experience and it is a time consuming process. In the absence of field data, the process of snow avalanche tracks mapping is influenced by the subjectivity of those who digitize. Thus, we propose a semi-automated method for detection of snow avalanche tracks based mainly on geomorphometric parameters that can be extracted from the Digital Elevation Model (DEM) like slope gradient, plan and profile curvature, mean curvature, runoff.In this study we used an object based analysis to detect snow avalanche tracks in central part of the Făgăraș Mts. This approach has two steps, segmentation and classification. First, we segmented the area based on plan curvature (which is the most important parameter that describes these snow avalanche tracks) in order to obtain objects. In the process of classification we added other conditions such as fuzzy function for slope gradient, thresholds for altitude and runoff and a shape index of objects. The results obtained were very close to the mapped tracks using digitizing techniques. The maps resulted from the classification were compared to the those resulted from digitizing in both number of objects and spatial agreement of the class of objects. There was a very good fit in case of the number of objects and total area of objects. The method could be improved if we apply on high resolution DEMs and also on more case studies with different topography and existing vector database.

Volume XI |

Trends in land cover change in abandoned mountain pastures. A case study: Măgura Marga Massif (the Southern Carpathians)

Abstract: Grazing was the main activity of the inhabitants of the region, so that on an area of only 750 hectares, 16 sheepfolds existed simultaneously. In the last 20 years, mountain pastures were gradually abandoned a fact which led to some changes in land cover, mainly close to timberline. The aim of this paper is to identify general trend of land cover change using change – detection methods based on Landsat TM imagery for 1988 – 2011 time interval. Detailed analysis based on field research and high resolution air photos was also made for the areas with highest land cover changes. The analysis of the historical maps allowed a better understanding of the land cover transformations in the last 70 years. The results showed that the general trend in pastures area for the last 23 years is the biomass gain. Even if this phenomenon has a low and medium magnitude, it is a dominant one, appearing on more than 88% of the pastures area. Moderate intensity changes are explained due to the relatively short time interval since pastures were abandoned. Major changes occurred in some areas: on the southern slopes, because of the specific topoclimate, in areas where the anthropogenic timberline was lowered at very low altitudes and in the areas near the spruce timberline. There are also areas where there are no obvious changes of the timberline. These occur more frequently on the northern and western slopes, near the beech forest timberline. In the study area, the timberline is still anthropogenic, but if the current trend of forest regeneration continues, the timberline will change to a climatic one.

Volume IX |

The Use of the Digital Terrain Model in Analyzing the Natural Potential of the Muntele Mic – Poiana Mărului – Ţarcu Mountains Tourist Area to Extend and Plan the Ski Domain

Abstract: The present study aims at examining the natural potential of the region as a prerequisite for the planning and the expansion of the ski domain, in order to reinvigorate the resorts Muntele Mic and Poiana Mărului. The factors taken into account to identify the best areas for planning new ski tracks are: the altitude, the slope, the orientation of the slopes to the solar radiation, the duration and the thickness of the snow layer, the land use, the risk of snow avalanches occurrence and the degree of accessibility. Because the factors considered don’t have the same importance for the favorability, before the combination of the factors, we used the Analytical Hierarchy Process (AHP) implemented by the IDRISI Andes software to assign for each factor a relative weight to use in the analysis. The risk of snow avalanches occurrence was considered as restrictive factor (Boolean factor). The combination of factors by Weight of Evidence method resulted in the creation of the final model, which presents the probability map for new ski tracks. The probability degree varies continuously in space, from a very high probability (255) to a very low probability (0) depending on the combination mode in a certain area of the considered factors and their weight. We considered as optimal areas only the areas with values above 200. The best areas to expand the ski domain are the detached secondary peaks of Muntele Mic towards north and the northern slopes of the Nedeia Ridge. These areas could allow for the development of certain ski tracks at least the same size as the ones of the Prahova Valley. The development of the ski domain in these areas will connect the two resorts, Muntele Mic and Poiana Mărului, and could increase the touristic potential of the study area.