FLOOD AND FLASH FLOOD ANALYSIS FOR BARTIN RIVER BASIN

Transcription

1 FLOOD AND FLASH FLOOD ANALYSIS FOR BARTIN RIVER BASIN Associate Professor Hüseyin TUROĞLU Istanbul Universty, Department of Geography Ordu Cad. No: Laleli, ISTANBUL ABSTRACT Largely damaged and injurious s and flash s of which frequency and strength features gradually show an increase, come into existence in city center of Bartın City. In this study, we are aiming to analyse s and flash s which cause weighty damages on this region s and Turkish economics. For this aim, Bartın River s Basin has been taken as scope of this study. In connection with analysis of s and flash s, data belongs to physical geography features of Bartın River s Basin and also faulty varieties and choices have been used. Analysis studies have been implemented by means of Geographical Information Systems and Remote Sensing Technologies and also satelite images and topographical maps in different scales have been used. Data obtained by means of this analysis demonstrates that geopraphical features of Bartın River s Basin has very adequate conditions for natural disasters such as s and flash s, therefore it also shows that increasing of their frequencies and strengths and turning into forms of natural disasters are taken root from faults arisen of utilization choices and types on the land. Digital Database Bed Layers belong to geographical features of Bartın River s Basin has been overlaid by, flash classifications and concerning, flash risk maps were prepared. Keywords: Bartın River, and flash, Geographical features, Geographic Information System. INTRODUCTİON Natural disasters such as s and flash s of which frequency and strength features show an increase year by year, occur and affect Bartın City (Fig.1). These hydrographic originated nautral disasters cause serious and weighty damages on Turkish economics as well as local people. A great deal of studies with different standpoints were investigated on s and flash s happen in Bartın City (Şorman, vd., 1998, Turoğlu, vd., 2004, Tüysüz, vd., 2004, Turoğlu, 2005). Within the context of this research we approached the matter from a standpoint of geographical perpective and aimed to analyse happened s and flash s based on Bartın River s Basin.

2 506 INTERNATIONAL CONGRESS ON RIVER BASIN MANAGEMENT In the course of this research, office studies and fieldworks have been implemented jointly. In the scope of office studies, forming of digital database, analysis of places and visualisation of results have been implemented and during fieldworks also applications such as measurement, analysis results and testing of prepared maps were realized. In the course of these studies topographical and geological maps in scales of 1/25.000, air photos in scales of 1/ belongs to the years of 1944 and 1998, Landsat 1975 MSS, 1987 TM satellite images, Bartın City s building development scheme in a scale of 1/5.000, all in all have been used as a database. Analysis studies were implemented by means of Geographical Information System and Remote Sensing Technologies. Floods and flash s cause damages in city center of Bartın City are actually natural events orientated by physical and human geographical features of Bartın River s Basin. Transformation of such natural events into natural disasters is a result of efficiency of humankind factor. For the aim of and flash analysis, it is planned to analyse such events by means of obtained database belongs to geographical characteristics of that basin. It is a preferential method to implement related studies and investigations on the media of Geographical Information Systems because of its advantages on data diversity and analysis opportunities (Knighton, 1996, Sarma, 1999, Gren, 2000, Hansson ve Ekenberg, 2002, Ekenberg, vd., 2003, Turner-Gillespie, vd., 2003, Turoğlu, vd., 2004, Turoğlu, 2005). Fig. 1: Digital Elivation Model of Bartın River s Basin.

3 RIVER BASIN FLOOD MANAGEMENT 507 Database and Analysis As geographical factors act a part on happening of natural disasters arisen from hydrographic origin, in the scope of physical geography the field s geomorphological (slope, aspect), lithological, climatological, hydrographical, plant and soil characteristics have been investigated and also in the scope of human geography; population and settling area of the basin, economical activities and field usage characteristics were studied (Fig. 2). BARTIN RIVER S BASIN Slope Aspect Drainage Climate Lithology Soil Vegetation Land Use Network Shape index Drainage pattern Drainage density Riverbed Weathering Permeability Rocks Structure Forest area Destroyed forest Shrubs Grasslands N, E, S, W NW, NE, SE, SW Flat Precipitation Temparature Wind Moisture Infiltrate Moisture Temparature Structure Texture Water holding capacity percolation Settlement Farming Vegetation Harbour Changing of drainage network Fig. 2: Database contents for Flood and flash in Bartın River Basin. Within the context of geomorphological features; slope and aspect characteristics of Bartın River s Basin have been classified in connection with and flash. Four slope classes have been distinguished. The slope value which holds the widest area is < 15% and it is described as perpendicular class (57,13%). The second slope which holds the second widest area is 0-2 % and this class is described as flat and hole areas (21,06%). Within the first class, s and flowings are more effective and within the second class of slope, inundations are more influential. Total value of these two slope classes represent 78,19% of Bartın River s Basin. Hillsides in directions of NE, N, NW and W are slopes which have short sunbathing times, weak sunbathing strengths, high cloudy situations, high humidity rates and low evaporations. Due to such characteristics, loss rate on surface flowing water amount is very low. These hillsides cover 41,48% of total area of the basin. Flat areas on which inundations play a part, cover almost a half of the remained area of the basin (24,54%). Hydrographic features which are parameters of physical geography of study area have much importance for sheet, torrent and disasters. Results of analysis of morphometric and slope features of Bartın River have shown a severly increasing character (Fig. 3).

4 508 INTERNATIONAL CONGRESS ON RIVER BASIN MANAGEMENT Fig. 3: Subbasins of Bartın River s Basin and drainage network features. Climatic features of Bartın River s Basin have been studied as precipitation, heat, wind and atmospheric moisture. Result of this study has been appeared that max. heats in July and August, max. precipitation as rain in September-November period, max. rain-fall caused natural disasters as strong rain-storms in May-July period (Table 1). The basin is usually effected from northerly winds but violent winds are effected from southwesterly with strong rain-storms (Fig. 4). Also, high atmospheric moisture attracts attention as one of the climatic components in Bartın River basin. Table 1:Ditribution of monthly precipitation(m 2 /kg) in Bartın River s Basin(D.M.İ.G.M, 2001). Year/ Mounth Total ORT ,27 68,91 59,09 59, ,73 91,27 115,6 125,9 106,2 120,1 1074

5 RIVER BASIN FLOOD MANAGEMENT 509 WNW W NW NNW N NNE NE ENE E W WN N NE E WSW ESE SW SE SW SE SSW SSE S S Fig. 4 : Frequent and strong winds directions in Bartın River s Basin. Mesozoic and Tertiary deposit units which are of thin grain structure and shelf deposits have been most widespread lithological unit of study area. Paleozoic metamorphic carbonate rocks appear in limited areas taking place in connection with Blacksea of Bartın River and its vicinity in basin. Quaternary sediments are widespread as fluvial precipitate forms in slope breaking, bed of Bartın River and vicinity. Four different soil types which are podsolic soils, without lime brown forest soil, brown forest soil and alluvial soil have been classified in basin. Almost all types of soils in the basin are of fine grain, impermeable and low infiltration capacity. It has been understood that devastate of natural vegetation of basin according to investigation of formerly documents. Actual forest area has been calculated as 34,7 percentage of Bartın River s Basin through Remote Sensing studies, fieldworks and other documents belonging to vegetation features of basin. Significant changes on field usage of Bartın River s Basin has been realized within the time period starting from 1944 till today. It is possible to classify such changes as settlings, agricultural areas, flora, port and drainage changes. In general there was scattered settlement on hillsides 60 year ago, but housings have been amassed on river beds in the time period of last 10 years. For instance whereas Bartın City s center had an area of 0,5355 km2 in 1944, as a result of area measurements obtained from 2003 dated satellite images it has been concluded that city center of Bartın City became 16,2762 km2 and this expansion was realized within and flash areas. Usage of agricultural areas for settling reasons and rapid destruction of natural flora are most significant changes on area utilization. Construction of Bartın City Port, due to taking no notice of region s climatic and drainage system characteristics, acts a very effective role on and flash events. By means of port construction, Bartın River has been canalized in order to be discharged in SW direction. But turbulent-stormy air masses which carry rainfall are

6 510 INTERNATIONAL CONGRESS ON RIVER BASIN MANAGEMENT in SW direction (Fig.4). Therefore this situation causes Bartın River which has 0,2% bed slope to inundate sea water course in boisterous weathers and it prevents discharge of Bartın River into the sea (Photo 1). Photo 1: Drainage network of Bartın River has been changed in basin. Changing for harbour construction was being most tragic. Because of artificial or natural filling, cross-section of Bartın River chanel have shrinked and water carrying capasity has became less then before. New circumstances have been effecting as increasing character on frequency and intensity of s and flash s in Bartın River Basin (Photo 2). Photo 2: Artificial filling cause to shrink of cross-section in the Bartın River channels.

7 RIVER BASIN FLOOD MANAGEMENT 511 CONCLUSİON : Flood and flash analysis of Bartın River Basin have been realized using geographic parameters of basin and obtained data have been summarized on Table 2. Also, and flash risk maps of Bartın River Basin have been produced according to data base (Fig. 5-6). The results taking place natural disasters such as sheet, flash and analyses is listed below. Too much water excising of caring capacity of riverbed bring about to natural disasters. This water is supplied from heavy rainstorm of frontal and orographic origin. Heavy rainstorms are affected together with strong SW winds. Geologic and geomorphologic features of Bartın River basin show encouraging features to natural disasters. Both water absorption capacity of basin and water loss due to surface ing is very poor. Drainage system of basin, size and rate of flow features; subbasin characteristics encourage torrent and s. Causes to hydrographic natural disasters which result in miss of land use types in harmonizing land potential are preferred by man is very important. Highest risk rate of each type of natural disasters such as sheet, torrent,, erosion and mass-movement is brought about percent in the basin. 19,02 percent of basin is under the highest risk of disaster rate. It is calculated that only 6,77 percent of basin have without natural disaster menace. Influenced area by means of hydrographic origin disasters such as torrents and s has been covering ,02 m2 and 50, 98 percentage in Bartın city. Torrent and safe areas cover ,66 m2 and 49, 02 percentage in Bartın city According to results of analysis, Unuseful areas having flash and risks for settlement cover percentage of Bartın city.

8 512 INTERNATIONAL CONGRESS ON RIVER BASIN MANAGEMENT Table 2: Table showing the main geographic factors and characteristics having important role for and flash in Bartın River Basin. Geograp hic Factors Slope Aspect Drainag e Network Climate Litholog y Soil Vegetati on Land Use Characteristics Description Impact on disaster Disater % 0 2 Low land, Level, Nearly level Strong water flow, big water body, ponding Inundation, % 2 5 Very gentle slope Strong water flow, water collection, % 5 15 Gentle slope Strong water flow, water collection, % 15 < Steep slope NE, N, NW, W, 41,48% E, SE, S, SW 33,98% Less sunlight for big part of basin, High moisture, less evaporation Flood, Flash Flash, sheet Flood, flash, sheet Flat 24,54% Strong water flow, water collection, Inundation, Flood Shape index Drainage pattern Sw=L/W=1,01 Dendritic Drainage density D=ΣL/A= 0,96 Very usefull conditions for water collection Riverbed Artificial filling Insufficient canal carring capacity Precipitation Heavy rainstorm Wind (Stormy) SW Unexpected and big mass water flowing surface Evaporation Low Moisture (Relative) 77 % (Average) More water flowing surface Weathering Strong More debris for sediment yield Permeability Poor Rocks Structure Infiltrate and percolation Moisture level Heat Structure Water holding capacity Sedimentary (90 %) Limeston, clay, silt, sand Poor Humid Medium Fine materials Medium 34,70% Forest Destroyed forest 27,67% Agricultural lands 36,00% More water flowing surface Less water missing but more water flowing surface Less water keep, more water flowing surface Settlement 1,62% Hinder to water flow Vegetation 62,37% Owing to destroyed forest, suitable condition for, flash and sheet. Farming 36,00% Low slope, flats or sunken lands help water accumulate Harbour 0,01% Hinder to discharge of water to Black Sea Inundation,, flash, sheet Inundation,, flash, sheet Inundation,, flash, sheet Inundation,, flash, sheet Flood, flash, sheet Inundation, Inundation,, flash, sheet

9 RIVER BASIN FLOOD MANAGEMENT Fig. 5: Flash risk map of Bartın River Basin. Fig. 6: Flood and inundation risk map of Bartın River Basin. 513

10 514 INTERNATIONAL CONGRESS ON RIVER BASIN MANAGEMENT REFERENCES Ekenberg, L., Brouwers, L., Danielson, M., Hansson, K., Johannson, J., Riabacke, A., Vari, A., 2003, Flood Risk Management Policy in the Upper Tisza Basin: A Siystem Analytical Approach Simulation and Analysis of Three Flood Management Strategies, International Institute for Applied Systems Analysis, Schlossplatz 1, A-2361 Laxerburg, Austria. Gren, C., 2000, Flood risk management in the context of Integrated Water Resource Management (IWRM), Hansson, K., Ekenberg,L., 2002, Flood Mitigation Strategies for the Red River Delta, Presented at The Commons in an Age of Globalisation, The Ninth Conference of the Internetional Association for the Study of Common property, Victoria Falls, Zimbabwe. Knighton, D., 1996, Fluvial Forms and Processes, ARNOLD, ISBN , GB. Nawaz, F., Shafique, M., 2003, Data integration for risk analysis by using GIS/RS as tools, Sarma,P., 1999, Flood risk zone mapping of Dikrong sub basin in Assam, Şorman, Ü., Gülkan, P., Önder,H., Yanmaz, M., Doğanoğlu, V., Erkay, C., Karaesmen, E., Yıldız, D., 1998, Batı ve Doğu Karadeniz Bölgeleri Sel afetleri Araştırma Raporu, Türkiye Müteahhitler Birliği, Ankara Turner-Gillespie, D.F., Smith,J.A., Bates, P.D., 2003, Attenuating reaches and the regional response of an urbanizing drainage basin, Advances in Water Resources, Volume 26, Issue 6, Pages , Elsevier Science B.V. Turoğlu, H., Özdemir, H., Gönençgil, B., Güneysu, A. C., 2004, Bartın Çayı havzasının Hidrografik doğal afet risk analizi, İstanbul Üniversitesi Bilimsel Araştırma Projeleri, Proje no: 1700/ , İstanbul. Turoğlu, H., 2005, Bartın da meydana gelen sel ve taşkınlara ait zarar azaltma ve önleme önerileri, Türkiye Kuvaterner Sempozyumu V, İTÜ/aybe Avrasya Yerbilimleri Enstitüsü, Sempozyum Kitabı, s: , İstanbul. Tüysüz, O., Genç, C., Tarı, U., 2004, Physical factors controlling urban planning disasterareas: Bartın, western Black Sea region, An International Interdiciplinary Conference on THE BLACK SEA REGİON: Past, Present and Future, October 14-16, 2004, List of Abstracts, 36-37, Istanbul, TURKEY.