Sürdürülebilir akarsu yönetimi için regüle edilmemiş batı Türkiye akarsularının hidrolik geometrisinin incelenmesi

Playing a major role in the geographic cycle, rivers are both the routes over which the erosion products are carried to the sea and the mechanism for effecting the transportation. Through decades, it is observed that, a complete cycle of healthy river life consists of successive stages of youth, adolescence, maturity and old age. At the stage of maturity, a river is very well able to attain the condition of grade that connotes the existence of equilibrium in the river system. Stream characteristics tend to adjust themselves to the discharge and sediment load. Therefore, if necessary, a healthy river restoration ought to aim to mimic the most natural condition as much as it could. For a sustainable river restoration, selection of river cross-section is vital since it has a great influence on determining the magnitude of flood for a given section; defining sediment characteristics and transport process mechanism; thoroughly understanding the riverine ecosystem and determining the velocity, which can affect fish community. The present work describes in quantitative terms the manner in which hydraulic geometry parameters change with discharge at a given unregulated/natural river cross-section and how environmental friendly river restorations and impact assessments can be figured out according to the river geometry. It has seen that some measured hydraulic characteristics of stream channels (width, depth, velocity, slope) vary with discharge as simple power functions at a given river cross section. The discharge related hydraulic geometry functions derived for a given cross section among various cross sections along the river differ only in numerical values of coefficients and exponents. An empiric quantitative relation among average measurements of width, depth, velocity and slope is derived from data on natural, unregulated rivers. Afterwards, characteristics of channel shape in the unregulated river cross sections are examined. At a given cross section with a gauging station, the bankfull width and depth and therefore, the velocity change with the amount of water flowing in the cross section. The changes in these geometric parameters seem to have certain characteristics which are applicable to many natural river cross sections. The data used in this study collected at regular river measurement stations for purposes of determining river discharge by State Hydraulic Works. This study uses hydraulic data surveyed in 14 unregulated reaches within six different river basins (Büyük Menderes, Küçük Menderes, Kuzey Ege, Susurluk, Meriç-Ergene, Gediz) in the Western Turkey. These river basins have similar meteorological characteristics in common, representing the western mediterranean region. Combining Google Earth features with the gauging station data which was provided by State Hydraulic Works, first of all, unregulated reaches and weakly regulated reaches were determined by excluding dams and weirs along the reach for the six different river basins. Secondly, among the determined total unregulated reaches on those river basins, usable reaches were selected according to the applicable gauging station data corresponding to them. After deciding the reaches and stations, SHW data were gathered together to calculate the cross sectional area for each of the river basin reach. For that cross section data, rating curves and flow duration curves were computed then. Coming to the formative discharge, two statistical analysis were done to decide the best correlated discharge with the channel geometry. Subsequently, empirical equations, coefficients and exponents were generated according to the relationship between discharge values and cross-sectional geometry. The generated empirical hydraulic geometry and flow expressions were tested within the unregulated Batı Akdeniz river basin for the validation purpose of the empirical results. Rivers tend to adjust and reconstruct themselves with their self healing capacity and if necessary, a healthy river restoration must mimic the most natural condition as much as possible. Overdesigning or enlarging the channel cross section (typically widening) can create a conflict in the large woody debris balance and may give rise to the thrash accumulation and eventually a slow death of a functioning river. For a sustainable river restoration, selection of river cross-section is vital since it has a great influence on determining the magnitude of flood for a given discharge; defining sediment characteristics and transport process mechanism and thoroughly understanding the riverine ecosystem. And with the help of flow patterns through history, a link can be established between the main river channel capacity and it's flow interaction so that a natural flow regime and it's relationship with cross-sections can be understood. Since formative discharges are main triggers of a typical cross-section of a river, this study is conducted to give a better understanding of hydraulic geometry parameters changing with discharge at a given unregulated river cross-sections located in Western Turkey and the results might be a transitional stage to the urban runoff planning and future works can be done to imitate unregulated river cross-sections where modified land use require different development strategies.