Risk assessment from flooding in the rivers of Albania (POSTER)

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ABSTRACT Flooding is a natural phenomenon in Albania. The floods are flashy and flood – waters occupy the floodplain; in the biggest rivers, close to the river mouth area, these waters inundate the floodplain for several weeks. Attempts have been made to alleviate flood situation in Albania by building protective dykes and creating upstream storage. Although many of these measures have been beneficial, they also served to encourage further encroachment upon river floodplains, thereby raising the potential for flood damage. Actually, more than half of the Albanian population lives very close to the river mouth areas, where the risk of flooding is higher. The structural solution is only a partial one; the only long-term solution consists of keeping flood-vulnerable development and uses out of the floodplain. In order to evaluate the flood potential, a statistical study in national scale was carried out. etc . MAIN ISSUES FROM FLOODINGS IN THE RIVERS OF ALBANIA Flooding is a natural phenomenon in Albania, resulting from an increase in stream flow beyond the point where the normal stream channel can contain the water. When water overspills riverbanks, it spreads out along the adjoining floodplain. Flood - waters may occupy the floodplain for a matter of hours, as in case of flash floods, or for several weeks, as sometimes occurs during the winter period, when the period of rainfall is longer or during the floods of spring period caused by snowmelt. . In an effort to provide a co-ordinated, cost –effective approach to the problem, there is a need to established Flood Damage Reduction Program, in order to ensure sustainable development, combining the following activities: • Mapping of flood – prone areas • restricting land use activities in the flood zone • educating the public • studying flood – prone areas to suggest mitigation, including structure where warranted • assisting in the implementation of flood forecasting. HYDROLOGICAL CHARACTERISTICS OF ALBANIA The climate of Albania, in general, is Mediterranean with some degree of continentality in the mountainous regions in the northern, central and southern part of the country. The country combines a coastal plain in the West with fairly high mountains: the highest point reaches 2751 m at the triple border with Yugoslavia and Macedonia, while many ridges exceed 2000 m in the northern, central and southern parts of the country. The rain comes mainly with south-west winds and falls according to the obstacles encountered. This gives a variety of climates and rainfall patterns in the different regions of the country, as show the values extracted for stations with 30 years of continuous observation: Average annual rainfall is around 1485 mm; the seasonal pattern is very consistent, with July, sometimes August, as the driest month and November, sometimes December, as the wettest one ; FIG. 1 HYDRO GRAPHIC MAP OF ALBANIA FLOOD POTENTIAL BASED ON HISTORICAL RECORDS The most important cause of floods is excessive rain. Rain may be seasonal occurring over wide areas, or from localised storms which produce the highest intensity rainfall. Melting snow is another major contributor to floods. The relief of Albania is mountainous with an altitude of 786 m. The precipitation regime is in general Mediterranean, characterised by intensive showers in winter and droughts in summer. In the highest part of the basin the precipitation, in the most part of them come down as snow. During the big floods the water overflow in the Western Plain of Albania, creating almost one river mouth. During the floods, the values of the specific discharge in the main rivers oscillate from 0.5 m 3 /s.km 2 ( Drini river) to 2 - 5 m 3 /s.km 2 ( Ishmi river) and in smaller rivers (A=100-400km 2 ) from 2 to 10 m 3 /s.km 2 .The floods are flashy and in the main rivers they traverse the hydro graphic network in 8-10 hours. Based on the information of historical records peak discharges and the volumes of the floods are computed for different return periods, which are presented for some stations of the low part of river watersheds.ig. 1 Hydro graphic map of Albania No River Station Surface of watershed River stage over“0” Discharge Period A(km²) H (cm) ( m3/s) 1 Buna Shkoder 4134 560 2000 13.1.1963 2 Drini Vau Dejes 11500 673 5180 13.1.1963 3 Drini Bahçellek 14173 564 * 4 Drini i Zi Kukes 4413 531 1080 13.1.1963 5 Drini i Bardhe Kukes 4314 553 1450 13.1.1963 6 Lana Tirane 20 302 159 16.11.1962 7 Erzeni Ndroq 640 584 794 16.11.1962 8 Erzeni Sallmonaj 719 971 956 16.11.1962 9 Shkumbini Murrash 1240 542 945 16.11.1962 10 Shkumbini Paper 1890 631 1430 16.11.1962 11 Semani Ura Kuçit 5080 714 * 16.11.1962 12 Osumi Ura Vajgurore 1870 774 1130 16.11.1962 13 Vjosa Dorze 5420 938 3650 3.2.1963 14 Vjosa Mifol 6680 652 * 18.2.1963 TABLE 2. FLOOD CHARACTERISTICS OF THE PERIOD NOVEMBER 1962 – FEBRUARY 1963 No Zone Inundated surface in ha Duration in days 1 Zadrima of Shkodres and Lezha , Bregu Bunes 18575 22 2 Fields between Drini of Lezha and Mati 3122 10 3 Fields between Mati and Ishmi ( Thumane etc) 5825 7 4 Fields downward Rogozhina in both river banks of Shkumbini 6896 7 5 Fields in both river banks of Semani 26738 35 6 Fields in both river banks of Vjosa downward Ura of Mifoli 3538 20 7 Total 64694 TABLE 3. INUNDATED ZONES DURING THE FLOODS OF NOVEMBER 1962- FEBRUARY 1963. FLOODPLAIN MAPPING IN THE WESTERN PLAIN OF ALBANIA The purpose of floodplain mapping is to delineate the area affected by a flood of a specified magnitude. Under the national Flood Damage Reduction Program, the flood hazard area should be subdivided into the floodway and the flood fringe. The first step in floodplain mapping involves the production of topographic maps for the basin under consideration. First, the river stages and the corresponding absolute quotas, with different return periods, were computed. Analysing and comparing these quotas with those of the flood of 1962-63, was noted that the highest river stages of this flood actually have a return period of around 100 years. Concerning the minimal scenario, it is presented by inundated zones, inside the space of the dykes, on both sides of the river. For this scenario an indicative map on the scale 1: 100 000 has been elaborated. Flooded Area Lakes Rivers Fig. 4 Flood Risk Map 100 Years Return Period CONCLUSIONS RELATED TO SOME FLOODING MITIGATION MEASURES As it is mentioned in the above paragraphs, the flood is a natural phenomenon in Albania. In these conditions only flooding mitigation measures could be taken in order to reduce the damages caused by flooding. These measures can be classified into two types: short-term measures and long-term measures. SHORT – TERM MEASURES They include maintenance works and organizative measures, aiming to warn as soon as possible the state institutions and population. These measures could be summarized as follows: • Measures for the improvement of the drainage systems and the channels of high water, especially the work of the pumping stations. • Organization of the Flood Warning Service in the Institute of Hydrometeorology. LONG-TERM MEASURES The establishment of a National Flood Damage Reduction Program is a priority. Some measures of technical character are mentioned as follows: • Identification of the state of dykes and necessary measures for rehabilitation and eventually, building of new structures on both riverbanks (partly in Drini and Buna, Shkumbini , Semani and Vjosa ). • Analyzing the current standards of the hydro-module. • Rehabilitation of existing dams in small irrigation reservoirs . • Reducing the high erosion rates by means of reforestation, building of small dams in the upper part of mountain torrents etc .,. Risk assessment from flooding in the rivers of Albania Agim Selenica 1 , Alban Kuriqi 2 , Mehmet Ardicioglu 2 1 Department of Hydrotechnic, Polytechnic University, Albania 2 Department of Civil Engineering, Epoka University, Albania 2 Department of Civil Engineering, Epoka University, Albania