Download PDF
Download page Applicability and Limitations of Transform Models.
Applicability and Limitations of Transform Models
The choice of a transform method should be coordinated with the purposes of the study and desired level of accuracy. When hydrologic data are carefully selected and used, the results obtained through the use of unit hydrograph transform methods are generally acceptable for practical purposes. In fact, throughout the world, hydrologic modeling guidelines specify or recommend the use of unit hydrograph theory (Institute of Hydrology, 1999) & (The Institution of Engineers, Australia, 2001).
Initial estimates of transform parameters should be subjected to a model calibration process where computed outputs are compared against observed data and model parameters are modified in order to achieve an adequate fit. Also, best estimate parameters derived through the aforementioned model calibration process should be tested through a model validation process where computed results, without any further parameter modifications, are used to compute outputs which are compared against observed data for independent events that were not considered during model calibration. Storm events used during both model calibration and validation should be approximately equal to the magnitude of events that are being considered within the particular application.
The following table contains a list of various advantages and disadvantages regarding the aforementioned transform methods available for use within HEC-HMS. However, these are only guidelines and should be supplemented by knowledge of, and experience with, the methods and the watershed in question.
Method | Advantages | Disadvantages |
---|---|---|
User-Specified Unit Hydrograph |
|
|
User-Specified S-Graph |
|
|
Clark |
|
|
Modified Clark |
|
|
Snyder |
|
|
SCS |
|
|
Kinematic Wave |
|
|
2D Diffusion Wave |
|
|