Hydrological Models¶
Catchment records include information related to hydrological modelling. Such information is shown in separate tabs: one tab for each model.
Hydrological models for catchments include two distinct classes of models:
- Surface runoff model: These are the most common types in urban runoff analysis. The common characteristic of all the models in this class is that only surface runoff is computed. This implies discontinuous runoff hydrographs where flow starts as a result of rainfall and reduces to zero again after the end of rainfall. As such, these models are suitable for relatively densely urbanized catchments with dominant amount of runoff generated on impervious surfaces, and for single-event analyses (e.g. design rainfall of certain recurrence interval). These models fail to provide realistic results in dominantly rural catchments and for long-term analyses involving multi-event rainfall series.
- Continuous hydrological models: These models treat the precipitation volume balance without any truncation through complex concepts. As a result, the generated runoff includes both the overland and subsurface runoff components. Due to longer time scales involved, the runoff hydrographs appear practically continuous. An important property of continuous hydrological models is hydrological memory, i.e. the ability to simulate the catchment reaction to certain rainfall dependent on previous rainfalls. This type of model is essential for any long-term analysis and for dominantly rural catchments. On the other hand, these models are usually incapable of simulating extremely fast response of heavily impermeable urban catchments.
MIKE+ includes a series of surface runoff models and one continuous hydrological model. The surface runoff models available are:
- Time-Area Method (A)
- Kinematic Wave (B)
- Linear Reservoir (C1 and C2)
- Unit Hydrograph Method (UHM)
- New UK / Wallingford
The continuous hydrological model included is Rainfall Dependent Infiltration (RDI).
Most of the surface runoff models can be used on their own, or in combination with RDI. When a surface runoff model is combined to RDI, the simulation will compute the runoff for each method (surface runoff model and RDI) separately as if they were different catchments, and will then sum the runoff of the surface runoff model and RDI model.
Combining different models for individual catchments in one runoff computation is also possible in MIKE+.
Detailed descriptions of the models are available in the following Sections and in the MIKE 1D Reference Manual.