coaltech upper olifants river catchment wetland inventory ...

In addition to the correlation between wetland distribution and geology in the UORC a
correlation between wetland type and geology has also been made by Palmer et al (2002).
According to Palmer et al (2002) most (92%) of the seasonally inundated channelled valley
bottom floodplains with footslope seepage wetlands were associated with drainage line
wetlands draining the southern watershed. The watershed is dolerite dominant. The
distribution of floodplain and valley bottom wetlands is influenced by the erosion and
weathering properties of the underlying geology (mostly shales and sandstone in the Vryheid
Formation). Seepage wetlands are closely linked to the permeability of the underlying
geology, as well as faults and contacts between different geological units (Palmer et al
2002).
Bedrock type has been used as an indicator of the distribution of pans in the world, the
bedrock type is, however not a very good indicator of the distribution of pans in South Africa.
It has, however, been found that pans mostly occur on shales and unconsolidated surface
sands. Pans occur mostly in areas without integrated drainage and with an average slope of
less than one degree. Although they are mostly scattered across the landscape, without any
obvious pattern, some occur linearly in the location of ancient rivers (Allan et al 1995).
3.2.2 Soil
The soil wetness and duration of wetness are an indicated by the colour of the soil. Grey soil
is an indication of wetness for prolonged periods of time and mottles indicate a fluctuating
water table. The permanent zone of a wetland is therefore characterised by grey soil, the
seasonal zone has a high frequency of low chroma mottles and the temporary zone has less,
high chroma, mottles. Soil in the terrestrial zone surrounding the wetland does not have
mottles in the top 50 cm of the soil (DWAF 2003a, Lizamore pers com 2005).
Due to the physical attributes indicative of wetness in the soil, some soil forms can be
classified as wetland soils. Soil forms indicative of the permanent zone of the wetland include
Champagne, Katspruit, Willowbrooke and Rensburg. While the following soil forms indicate
the seasonal and temporary zones of a wetland, Inhoek, Tsitsikamma, Houwhoek, Molopo,
Kimberley, Jonkersberg, Groenkop, Etosha, Addo, Brandvlei, Glenrosa, Dundee and various
others soil forms displaying mottling in the top 50 cm (DWAF 2003a).
Wetland Database for UORC - 16 -