16 Figure 3. Relationship of each Hydrologic Component
Source : http:www.sbg.ac.atgeoidrisigis_environmental_modeling sf_paperscollins_fredcollins.html
2.2.4 Classification of Hydrology Modeling
Watershed models are developed for different purposes. Nevertheless many of those model share structural similarities, because their underlying
assumptions are the same, and some of the models are distinctly different. The watershed models can be classified according to different criteria that encompass
process description, scale, and technique of solutions. The watershed model can be classified based on the time scale of models.
One of the time intervals is used for input and internal computations. The second is the time-interval used for the output and calibration of the model. Based on
these description, the models can be classified as 1 continuous-time or event based, 2 daily, 3 monthly, and 4 yearly models Sigh, 1995.
17 The watershed can also classified depend on the space of watershed.
These criteria is use to classify into small watershed, medium size watershed, and large watershed. For consideration of runoff generation on these watersheds, two
phases can be considered: 1 land phase and 2 channel phase. Large watersheds have well developed channel network and channel phase, and thus, channel
storage is dominant. The other hand, small watershed have dominant land phase and overland flow, have relatively less conspicuous channel phase, and are highly
sensitive to high- intensity, short-duration rainfalls. Watershed can be classified base on land use. Watershed can be classified
into agriculture, urban, forest and range land, desert, mountain, coastal, wetlands and mixed area. In many case, large or even medium size of watersheds have
mixed land use. These watersheds behave hierologically differently, indeed so differently that they have given rise to different branches of hydrology.
And frequently watershed model classified on the basis of their intended use. Model are classify into: 1 planning models, 2 management models, and 3
prediction models. A comprehensive watershed model can be employed to accomplish a considerable array of analytical tasks for planning and management
of water resources Viesman, 1989.
2.3 Flood 2.3.1 Flood Definition
