Grassed areas

This is the name given in the Horton (ILSAX) hydrological model within DRAINS to pervious areas, whether on not they are covered with grass. They might be lawns, bare soil, bushland, gardens, landscaped areas or even pervious pavements. The Horton (ILSAX) infiltration model is used to calculate hydrological losses on such areas.

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 Note that the lag time in the Sub-Catchment property sheet can be used to define where the grassed area is located in a sub-catchment.

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• Supplementary areas

  This is the term given in the Horton (ILSAX) hydrological model to impervious areas that are not directly connected to the pipe system. It includes areas such as tennis courts and concrete paths that are surrounded by pervious (grassed) surfaces, so ...

• Paved areas

  In general, this refers to land surfaces that are covered with impervious materials such as asphalt or concrete (although it may sometimes be applied to semi-pervious surfaces covered by paving blocks). In DRAINS it is the term given (for ...

• Depression storage

  This is a depth of rainfall (mm) that is assumed to be retained in depressions or puddles on a catchment surface and evaporated. It is a kind of initial loss, but it may be assumed to occur after infiltration, so that in the Horton (ILSAX) ...

• Lag time (Lag factor)

  In hydrology, catchment lag or delay has a general meaning, as the time taken for runoff in general to flow off a catchment to its outlet. It relates to the time difference between the centroids of the rainfall hyetograph and the runoff hydrograph. ...

• Horton (ILSAX) Hydrological Model property sheet

  This window enables you to enter, view or edit rainfall-runoff models. The data involved are: the name of the model (e.g. Manly Beach Model), depression storages (mm) for paved, supplementary and grassed areas, a soil type for the grassed or pervious ...