Geology and Topography

Terrain

Most of the Wet Tropics FBP has a high relief ratio, with a mean for the province of 0.06 . Low relief ratio values are confined to small patches within the province, particularly the western (Atherton Tablelands) part and the mouth of the Herbert catchment and the south eastern part of the Jeannie catchment. Stream segment slope values throughout the province are also on average very high, with lower values corresponding to areas with low relief ratio values.

The generally steep relief and high stream slopes results in steeper catchments where run-off is generally faster, producing more peaked discharges and greater erosive power (Thorne, 2004). This contributes to high disturbance intensity of spates in the province.

The province is strongly dominated by the erosional flatness index class. Only a small proportion of the province contains valley bottom flat areas (in the areas with low relief ratio), and ridge top flat is almost absent.  The dominance of erosional areas and steep relief is likely to result in the prevalence of coarse bed material in Wet Tropics streams and implies a dominance of aquatic assemblages preferring coarser substrate types at the province scale. Any biota preferring depositional areas are likely to be restricted in this province. The limited extent of valley bottom flats suggests floodplains and the processes associated with floodplain inundation are not likely to be important to the ecology of Wet Tropics rivers.

In depositional areas turbidity typically limits light penetration and prevents the occurrence of submerged macrophytes as well as limiting benthic production to the euphotic margins. The scarcity of depositional areas in the Wet Tropics province is likely to be associated with the relatively low turbidity of the area and subsequently the widespread distribution of submerged macrophytes.

Information about terrain

Information about methods

Wet Tropics FBP Terrain Maps   State Terrain Map