BazTech - Yadda

1

Separation of surface flow from subsurface flow in catchments using runoff coefficient

Ardekani A. Afshar, Sabzevari T., Haghighi A. Torabi, Petroselli A.

Acta Geophysica

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2021

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Vol. 69, no. 6

2363--2376

EN

Separating surface flow (SF) from subsurface flow (SSF) based on direct runoff measurements in river gauges is an important issue in hydrology. In this study, we developed a simple and practical method, based on runoff coefficient (RC), for separating SF from SSF. RC depends mainly on soil texture, land use and land cover, but we also considered the effect of slope and rainfall intensity. We assessed our RC-based method for three different soil types by comparing the value obtained with laboratory rainfall simulator data. The correlation coefficient between observed and calculated data exceeded 0.93 and 0.63 when estimating SF and SSF, respectively. The method was then used to separate SF and SSF in two catchments (Heng-Chi and San-Hsia) in Northern Taiwan, and the results were compared with those produced by the geomorphological instantaneous unit hydrograph (GIUH) model. Test revealed that, if RC is calculated accurately, the proposed method can satisfactorily separate SF from SSF at catchment scale.

2

Development of the Nash instantaneous unit hydrograph to predict subsurface fow in catchments

Babaali H. R., Sabzevari T., Ghafari S.

Acta Geophysica

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2021

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Vol. 69, no. 5

1877--1886

EN

For many permeable catchments with proper plant cover, subsurface flows play a key role in generating surface runoff. In this regard, developing subsurface flow models is of great importance and requires further studies. In Dunne-Black mechanism, it is subsurface flow causing saturated zone in hillslopes and generating surface runoff. The Nash model is an instantaneous unit hydrograph (IUH) model commonly used to predict the surface runoff. In this study, the Nash model was applied to estimate subsurface flow hydrograph in the catchments. The parameters of the subsurface Nash IUH (SNIUH) model were determined by developing of the subsurface travel time equations with the concept of celerity. The efficiency of the SNIUH model was verified by two rainfall simulator laboratory models. The mean error of the peak subsurface flow estimation ranged from 6.7 to 11.21% for both laboratory models, which was acceptable. Ultimately, the SNIUH model was used to estimate the subsurface flow hydrograph in Heng-Chi and San-Hsia catchments in Taiwan, and the results were compared with results of the subsurface geomorphologic IUH (SGIUH) model. The coefficients of efficiency (CE) of SNIUH were higher than 0.9 in four events for both catchments and the subsurface peak error values were between 10 and 16%.

3

Effect of hillslope topography on soil erosion and sediment yield using USLE model

Sabzevari T., Talebi A.

Acta Geophysica

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2019

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Vol. 67, no. 6

1587--1597

EN

Catchment hillslopes in nature have a complex geometry. Complex hillslopes have different plans (convergent, parallel and divergent) and different curvature (straight, concave and convex). In this study, the erosion rates of the nine complex hillslopes were investigated using the universal soil loss (USLE) method. The topography factor (LS function) in the USLE was developed as a function of plan shape and profile curvature. The hillslopes studied were divided into sets of complex pixels and the erosion over the pixels was calculated. Total erosion was regarded as the sum of erosion of all pixels. Furthermore, to calculate the sediment delivery ratio of each pixel, a new travel time equation for complex hillslopes was employed. Results showed that the mean erosion of convex hillslopes was 1.43 times that of concave and 1.19 times that of straight slopes. The effect of curvature shape on erosion was much greater than plan shape effect. The highest erosion belonged to convex divergent slopes, and the least erosion was related to concave divergent slopes. The laboratory results intended for validation of the numerical model also show that in hillslopes with fixed plan, the erosion rate in the convex hillslopes exceeds that of concave and straight hillslopes. Also, in the hillslopes with fixed curvature profile, the erosion rate in the convergent hillslopes is more than in the divergent and parallel ones.