A few categories of rainfall-runoff models are described by the model .. ecological and biological relationships in the water environment (Kokkonen et al., . and runoff outputs where Ia is initial abstraction, S is the retention parameter, . by lumped models are used for regulatory purposes that look at long-term conditions. Abstraction is the term used to describe the amount of rainfall that doesn't turn infiltration losses with initial abstraction based on the following relationship: Based on the above equation, P must exceed S before any runoff is generated . PDF | The rainfall-runoff relationship is helpful in forecasting runoff rate and runoff depth. The forecasted runoff can KEY WORDS: Rainfall-runoff relationship, remote sensing, runoff, Soil The ratio of initial abstraction (Ia) to.
Abstraction - Engenious Systems, Inc.
In the SCS method, the abstraction coefficient is not limited to a single loss type, but is a catchall for evaporation, interception, infiltration, and surface depression.
For the case where the abstraction coefficient is 0.
The groups are defined are: HSG A low runoff potential. These soils are characterized by high infiltration rates even when thoroughly wetted and consists of deep, well to excessively drained sands or gravels. These soils have a moderate infiltration rate when thoroughly wetted.
SCS Runoff Curve Number Method - Introduction - Professor Patel
They are moderately deep to deep, moderately well to well drained with moderately fine to moderately coarse texture. These soils have slow infiltration rates when thoroughly wetted.
They typically consist of soils with a layer that impeded downward movement or soils with moderately fine to fine texture. HSG D high runoff potential.
These soils have a very slow infiltration rate when thoroughly wetted. They consist mostly of clay with high swelling potential. These soils also have high water tables, or are soils with a clay pan or clay layer at or near the surface and shallow soils over nearly impervious material.An Introduction to Linear Regression Analysis
The AMC is defined as the amount of rainfall in a period of five to thirty days preceding the design event. AMC I — Soils are dry, but not to the wilting point. In the time elapsed since its original development, the NRCS runoff curve number method has become a de facto standard in hydrologic engineering practice, with numerous applications in the U. Its popularity is based on its simplicity, although reasonable care is necessary in order to use the method correctly.
In many instances, the method's capabilities have been stretched, mostly for lack of an alternative. Mockus pointed out that the method was not intended to be a predictor of the rate of infiltration, but rather, of the total volume of infiltration for a given storm event Ponce, Mockus stated that the supporting data used in the method's development was daily rainfall, because this type of data was the only one available in large quantities Ponce, In practice, this means that the RCN method ought to work best when the storm duration is close to 1 day, although in many applications this has not been necessarily the case NRCS, The emphasis is on the effect of initial abstraction in reducing total runoff Q ordinateand not on applying the initial abstraction to rainfall abscissa.
Therefore, for a given curve number CN, the storage S and initial abstraction Ia are also constants, regardless of the storm duration. Like P, S, and Q, the initial abstraction Ia is a volume, interpreted as a fraction of storm depth evenly distributed on the watershed under consideration.
We argue here that if CN and S do not account for either the rate of infiltration or the storm duration, neither should the initial abstraction Ia. On this premise, it appears unwarranted to place the initial abstraction at the beginning of the storm.
We reckon that the RCN method is lumped in time, originally developed for storm durations of 24 hr, and subsequently extended by way of practice to storms of lesser duration.