The shape of the hydrograph is influenced by the following variables:

    • Area
    • Slope
    • Roughness
    • Urbanisation (expressed as percentage impervious)
    • Rainfall loss model

In this tutorial, the following charts are used:

The values shown in these charts use the rainfall intensities and patterns for Cairns, in north Queensland. They are used to show the general behaviour of the model. Consider creating similar curves using the temporal patterns for your project area.

Percent Impervious on Various Slopes

Flat slopes are more affected by changes in percentage of Impervious area.

Manning’s n values on Rural Catchments with Various Slopes

Manning’s n values on rural catchments can have a significant effect on peak flows.

Manning’s n values in Urban Areas

Manning’s n values in highly urbanized areas have less effect as the slope is greater than 1%.