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Application of SCS-CN for Estimating Runoff on Arid Watershed
Published in Saeid Eslamian, Faezeh Eslamian, Flood Handbook, 2022
Sachin Kumar Behera, Sandeep Samantaray, Abinash Sahoo, Dillip K. Ghose, Saeid Eslamian
Antecedent moisture condition (AMC) is the moisture content present in the soil at the beginning of the rainfall-runoff event under consideration. The initial abstraction and infiltration are controlled by AMC. The practical applications of three levels of AMC are recognized by SCS as follows: AMC I: Soils having no wilting point and existing in a dry condition satisfied for cultivation.AMC II: Soils put on average conditions applicable for the average rate of cultivation.AMC III: Sufficient rainfall occurrence within the intermediate past five days prevailing saturated soil condition.
Infiltration and soil moisture
Published in Stephen A. Thompson, Hydrology for Water Management, 2017
Topography modifies infiltration directly and indirectly. Slope angle directly affects infiltration because steep slopes promote rapid surface runoff giving the water less time to infiltrate. Indirectly, elevation and slope aspect influence vegetation, soil development and antecedent moisture conditions. South-facing slopes in the northern hemisphere are usually dryer and support a sparser vegetation cover than northfacing slopes. Finally, the role of precipitation must be considered. If the rate of water supply to the surface (rainfall intensity) i is less than the infiltration capacity fp, then the actual infiltration rate equals the supply rate (f = i). Only when the supply rate exceeds the infiltration capacity can the actual infiltration rate equal the infiltration capacity. Other factors influencing infiltration have been identified including soil and water temperature and hydrophobic coatings on soil particles (Garstka 1978).
Environmental Evaluation: Lessons Learned from Case Studies
Published in Saeid Eslamian, Faezeh Eslamian, Handbook of Drought and Water Scarcity, 2017
Antecedent precipitation too often remains a subjectively determined and arbitrarily implemented parameter in rainfall–runoff modeling. Antecedent moisture can account for a severalfold difference in runoff from the same storm in an otherwise identical watershed. The antecedent precipitation index and the Natural Resource Conservation Service’s antecedent moisture condition triad are conventional expressions of antecedent precipitation. Unfortunately, neither index consistently characterizes the runoff consequence of watershed moisture preceding a rainfall event. A normalized antecedent index modifies the conventional index in three aspects: inclusion of antecedent precipitation earlier in the day of the event, normalization to the station mean, and normalization to the antecedent series length. This index based on daily rainfall record is theoretically simple and mathematically continuous. Initial results show the index to outperform single-curve number-based results, even when the current number is fit to historic rainfall–runoff records. In addition, this index enhances delineation of the antecedent moisture condition for estimates based on that parameter and provides a basis for runoff estimates where the initial watershed moisture condition is probabilistic [26].
Predicting rain garden performance under back-to-back rainfall conditions using stochastic life-cycle analysis
Published in Sustainable and Resilient Infrastructure, 2021
Reshmina William, Paolo Gardoni, Ashlynn S. Stillwell
Importantly, antecedent moisture is a highly variable parameter that is controlled by a variety of factors including the spacing of storms, the magnitude of storm events, and soil properties such as the saturated hydraulic conductivity. Because antecedent soil moisture has a significant impact on performance, timing and inter-storm duration for smaller events can be important metrics for assessing performance (Wadzuk et al., 2017). In other words, green infrastructure can underperform even for small storms if there is a short enough inter-storm duration. At the catchment scale, changes in antecedent moisture during a continuous simulation were compounded by uncertainty in other calibration variables (Avellaneda et al., 2017). Moreover, calibration measurements of soil moisture conducted by Avellaneda et al. (2017) indicated that soil moisture is characterized by high spatial variability. Other field and modeling studies highlight that antecedent moisture is highly variable in both time and space, making the accurate characterization of this variability critical to understanding runoff processes in catchments (Brocca et al., 2008; Meyer et al., 2011).
Revisiting 2013 Uttarakhand flash floods through hydrological evaluation of precipitation data sources and morphometric prioritization
Published in Geomatics, Natural Hazards and Risk, 2022
Pratiman Patel, Praveen Kumar Thakur, Shiv Prasad Aggarwal, Vaibhav Garg, Pankaj Ramji Dhote, Bhaskar Ramachandra Nikam, Sabyasachi Swain, Nadhir Al-Ansari
The maximum retention (S) is determined using the following equation: where is the SCS CN, a value that provides the ability of the surface to generate runoff. It is a function of soil group, LULC, and antecedent moisture conditions. The values lie in between 0 and 100. Higher the values of more the runoff generation ability and vice versa.