Evaluation of Precipitation and Soil/Land Use Parameters Affecting Flood Analysis in the Eskipazar Stream Example (Karabük, Türkiye)

Abstract

Flood risk is among the disasters that can lead to significant loss of life and property, especially in basins with rivers flowing near residential areas. Therefore, identifying accurate discharge estimation methods to mitigate this risk is of great importance. In this study, the effect of the Curve Number (CN) and Pluviograph (PLV) coefficient on peak flood disc-harge (Qp) estimations was evaluated for the Eskipazar Stream basin. Basin modeling was conducted using digitized 1:25,000 scale topographic maps through the NetHydro module of the NetCAD software. Since there is only one stre-amflow observation station established in the basin a few years ago, flood discharges were determined using precipitation data. The CN and PLV values play a critical role in converting precipitation data into streamflow data. In the study, peak flood discharges (Qp) for return periods ranging from 2 to 1000 years were calculated using the DSİ Synthetic Unit Hyd-rograph and Mockus Unit Hydrograph methods. It was found that increasing the CN value from 78 to 80 significantly raised the flood discharges, and that variations in PLV values also caused considerable changes in discharge. Considering the basin area of approximately 660 km², the DSİ Synthetic Unit Hydrograph method emerged as the most suitable app-roach, offering more consistent and realistic discharge (Qp) estimations compared to other methods. In cases where stre-amflow data are insufficient, it is recommended to use CN values derived from the joint evaluation of streamflow and precipitation data in nearby basins with similar hydrological characteristics. Additionally, for determining the PLV coeffi-cient, data from the meteorological observation station that best represents the basin should be used

Keywords

• Eskipazar Stream (Karabük) Basin
• Flood Analysis
• DSI Synthetic Method
• Mockus Method
• CN (Flow Curve Number)
• PLV (Pluviograph) coefficient

Evaluation of Precipitation and Soil/Land Use Parameters Affecting Flood Analysis in the Eskipazar Stream Example (Karabük, Türkiye)

Abstract

Flood risk is among the disasters that can lead to significant loss of life and property, especially in basins with rivers flowing near residential areas. Therefore, identifying accurate discharge estimation methods to mitigate this risk is of great importance. In this study, the effect of the Curve Number (CN) and Pluviograph (PLV) coefficient on peak flood discharge (Qp) estimations was evaluated for the Eskipazar Stream basin. Basin modeling was conducted using digitized 1:25,000 scale topographic maps through the NetHydro module of the NetCAD software. Since there is only one streamflow observation station established in the basin a few years ago, flood discharges were determined using precipitation data. The CN and PLV values play a critical role in converting precipitation data into streamflow data. The novelty of this manuscript lies in explicitly analyzing the influence of CN and PLV parameters on flood discharge estimations, an aspect that has been rarely comparatively emphasized in previous studies. In the study, peak flood discharges (Qp) for return periods ranging from 2 to 1000 years were calculated using the DSİ Synthetic Unit Hydrograph and Mockus Unit Hydrograph methods. Considering the soil properties, hydrogeological features and land use of the basin, it was found that increasing the CN values from 78 to 80, which is within the range of preferable values, significantly increased the flood discharges and similarly, considering the climate characteristics, the changes in the PLV values, which can represent the study basin, which presents a transition between the Black Sea climate (marine) and the Central Anatolian climate (continental), also caused significant differences in the discharge. In the study area, with a basin size of approximately 660 km², the Mockus method yielded higher peak discharges compared to the DSI Synthetic method. This outcome highlights methodological differences and the inherent uncertainties associated with the applied approaches. According to the literature, the DSI method is recommended for basins ranging from 10 to 1000 km², whereas the Mockus method is generally suggested for basins smaller than 10 km². Therefore, in this study, the results obtained from the DSI Synthetic method are considered to provide a more reliable estimation of peak discharge. In cases where discharge data are insufficient, as in the study area, it is recommended that the most appropriate CN values be determined by considering not only the soil, hydrogeological, and land use characteristics of the basin, but also the CN values obtained through comparative evaluation of discharge and precipitation data from nearby basins with similar characteristics. Furthermore, PLV values should be derived from meteorological stations that most accurately represent the basin, since alternative choices were shown to considerably increase discharge estimates, especially for short-duration storms.

Keywords

• Eskipazar Stream (Karabük) Basin
• Flood Analysis
• DSI Synthetic Method
• Mockus Method
• CN (Flow Curve Number)

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