FLOOD RISK AND HAZARD MAPPING FROM THE PERSPECTIVE OF THE PRESENT LEGISLATION. CASE STUDY: BÂRLAD WATERSHED (ROMANIA)
ISBN 978-85-88783-11-9
Authors
1Nedelea, A.; 2Laura, C.; 3Munteanu, A.; 4Luminita, S.
1UNIVERSITY OF BUCHAREST Email: alexndelea10@yahoo.com
2UNIVERSITY OF BUCHAREST Email: lauracomanescu@yahoo.com
3UNIVERSITY OF BUCHAREST Email: munteanca@yah
4UNIVERSITY OF BUCHAREST Email: luminitacostina@yahoo.com
Abstract
Our approach is intended to map the flood risk and hazard in the Bârlad watershed (Romania) by using the methodolgy enforced by Government Decission 447/2003 with subsequent changes, the Floods Directive 2007/60/EC of the European Parliament and the Medium and Long Term National Strategy for Flood Risk Management. Bârlad watershed is located in the eastern part of Romania, having a total area of 7,220 km2 (accounting for 3% of the Romanian territory) and a hydrological regime specific for the semi-arid temperate climate, with low discharges in summer and floods during the springtime. This area is very complex in terms of the existence of extreme discharges, which often make the river overflow its banks. The methodology enforced by the Romanian legislation points at two types of maps – flood hazard and flood risk – which are part of the Flood Risk Management Plans at watershed level. To develop correctly the two types of maps it is necessary, on the one hand, to identify the subbasins prone to floodings, which may bring about property damage and loss of lives, and on the other hand, to spot the causes, as well as the genesis and transit areas of the respective floods. Based on the location of these areas, one can make a regionalization of flood hazard on river stretches depending on the frequency of the main floods. The flood vulnerability of these areas is controlled by the topography and the location of the social-economic units within the watershed. Flood risk assessment was accomplished in the field by using specific mapping equipment. Flood hazard maps are representations showing the flood-prone areas adjacent to the rivers’ floodplains, with various exceedence probabilities, while flood risk maps show both the level of flood risk and the potential property damage and human casualties at administrative-territorial level. Both maps are made in GIS environment by integrating the information provided by maps and land surveying, the geological, geomorphological, climatic, hydrological and soil conditions, as well as the data regarding stream engineering works, slope improvement, deforestations etc. The flood hazard map made at scale 1:25,000 shows the flood-prone areas. For our case study, we focused mostly on the southern part of the watershed, where a number of torrential basins oocur. The preparation of flood risk maps relies on hazard maps and on the elements that might be endengered in the event of overflowings (people and material properties). The development of such a map must follow several steps: preparing the flood risk maps; making an inventory of the flood-prone property; estimating the number of people that might be affected; and assessing the risk based on the vulnerable elements and the hazard’s features. Our flood risk map is also of scale 1:25,000 and covers the same area as the hazard map. It shows three categories of areas: major risk areas (the Negrești-Vaslui stretch, which experienced the highest flood in 1985), medium risk areas and low risk areas. Detailed mappings were accomplished for the areas falling in the first category in order to prevent possible damage and loss of life. An important issue was the identification of the previous flood events (1965, 1969, 1970-1971, 1975, 1981, 1985, 1987, 1988, 1996, 1997, 1999, 2005 and 2007) and the human and material damage they brought about. This contribution is part of the VULMIN Project (type PCCA/52/2012) managed by Professor Dr. Alexandru Nedelea.
Keywords
hazard; flood; legislation