Mô hình hóa là trung tâm để quyết định nhiều thủy văn, phân tích và thiết kế. Các quyết định trong thủy văn kỹ thuật thường yêu cầu phát triển của một mô hình mới hoặc sử dụng một mô hình hiện có. Khi phát triển một mô hình mới, phản ứng của mô hình chặt chẽ nên bắt chước các phản ứng của hệ thống thế giới thực được mô hình hóa. Trước khi sử dụng một mô hình hiện có, xây dựng mô hình nên xác minh rằng mô hình thích hợp để giải quyết các loại vấn. | 12 Sensitivity Analysis INTRODUCTION Modeling is central to many hydrologic decisions both in analysis and in design. Decisions in hydrologic engineering often require the development of a new model or the use of an existing model. When developing a new model the response of the model should closely mimic the response of the real-world system being modeled. Before using an existing model the modeler should verify that the model is appropriate for solving the type of problem being addressed. When a modeler uses an existing model developed by someone else the modeler should be sure that he or she completely understands the way that the model responds to the input. In all of these cases the modeler should understand the model being used. Sensitivity analysis is a modeling tool that is essential to the proper use of a model because it enables the model user to understand the importance of variables and the effects of errors in inputs on computed outputs. Questions such as the following can be answered by performing a sensitivity analysis Which are the most important variables of a model What is the effect of error in inputs on the output predicted with the model What physical hydrologic variables are most likely related to fitted model coefficients In calibrating a model are all of the model coefficients equally important to the accuracy of the model Each of these questions suggests a relationship between two or more variables or the effect of one factor on another. In modeling terms they are concerned with sensitivity whether it is the sensitivity to errors the sensitivity of goodness-of-fit criteria or the sensitivity to watershed characteristics. Questions such as those presented above can be answered by applying an important modeling tool specifically sensitivity analysis. Of special interest in hydrologic analysis is the detection of effects of land use change. Watershed change can cause abrupt or gradual change in measured flood data or in characteristics of
