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C. Generation of the flood modelHEC-RAS is a one-dimensional software in which thesteady and unsteady streams are modeled [5]. Geometric datafor the Stream basin and data for the stream have to be enteredin order to conduct the modeling [7]. Geometric data pertinentto the study field were generated using HEC-GeoRAS andother data were completed in this section. Subsequently thedata was transferred to HEC-RAS software. After completingthe entry of geometric data, stream data for the Stream in thearea in which modeling was to be conducted were entered.Stream data for the repetition frequencies of floods wereaccepted as steady flow data. Since the gradient value of thestudy area was not very high, sub critic was selected for streamcalculation. Subsequently, models for 10, 50, and 100 yearswere generated (Fig. 7 and 8).Figure 7. Models of different flood repetition frequencies (with buildings).Figure 8. Models of flood repetition on 3D model.determining land use, demonstrating changes in land use,determining the Stream basin characteristics, and creatinggeometrical data for the floods. As the study area is a basinwith flood risk potential any flood taking place maysignificantly impact the settlement areas, industrial zones, andproductive agricultural fields. In the hydrologic and hydraulicmodeling conducted for flood risk studies, flood rates for 10,50, and 100 years were calculated using maximum flood ratesfor 33 years, and flood risk maps were generated throughhydraulic modeling using the values obtained. It is essential toexamine the floods and flash-floods, which impact on theYeniciftlik stream basin within the scope of more local andlong-term studies. The occurrence of floods and flash-floodsin the Yeniçiftlik stream basin and other disaster typestriggered by them is linked with the surplus water when thecarriage capacity of the Yeniçiftlik stream is exceeded.Geomorphologic characteristics of the basin (slope, aspect,drainage, etc.) are a suitable environment for natural disastersof hydrographic origin. Erroneous land use has significantnegative impact on the occurrence of disasters relatedto flood and flash-floods in the basin. Establishment ofsettlement areas inside the valleys and creation of agriculturalfields on the basin bed appear to be the most misguidedpractices. Filling of the Stream bed with fill materials andnarrowing the bed decrease its water carriage capacity. Due tothe risk of flooding in the coming years it will be necessary totake relevant precautions in this area and implement themrapidly. It has also been determined that in order to conduct amore realistic modeling using HEC-GeoRAS and HEC-RAShydraulic software, further data would be required.REFERENCES[1] Baker, V.R. And Pickup, G., Flood Geomorphology Of The KatherineGorge, Northern Territory, Australia. Geol. Soc. Am. Bull. 98, 1998, Pp.635-646.[2] Chow, V. T., Open-Channel Hydraulics, Mcgraw-Hill, Inc. New York,NY, 1959, Pp. 197.[3] Hyndman, D., Natural Hazards And Disasters, Thomson HigherEducation, Australia, 2006., Pp. 297-325, Pp. 197-227,[4] Fleckkenstein, J., 1998. Using GIS To Derive Velocity Fields AndTravel Times To Route Excess Rainfall In A Small-Scale Watershed,Univ. Of California Davis. Http://Scs.Ucdavis.Edu. (Accessed 08.03.2008).[5] Merwade, V., Tutorial On Using HEC-Georas With Arcgis 9.1 PreparedBy School Of Civil Engineering, Purdue UniversityWeb.Ics.Purdue.Edu/~Vmerwade/Education/Georastutorial.Pdf 2006,Pp. 20-30 (Accesed 24.04.2008).[6] Fasken, G., Guide For Selecting Roughness Coefficient “N” ValuesFor Channel, United States Department Of Agriculture, SoilConservation Service, Lincoln Nebraska, 1963, Pp. 45.[7] Özdemir, H., Floodplain Mapping Using Hec-Georas And Hec-Ras: ACase Study Of Havran River (Balıkesir).Http://Www.Cbs2007.Ktu.Edu.Tr/Bildiri/S_33.Pdf, 2007, Pp. 6,(Accessed 15.05.2008).IV. CONCLUSIONIn this study an area of 3.66 km 2 in the Yeniçiftlik streambasin was examined. Flood risk analysis was performed usingRemote Sensing and GIS. Remote Sensing data were used in