coaltech upper olifants river catchment wetland inventory ...

3.4.1.2 Floodplain riparian
Floodplain riparian wetlands occur in lower-lying areas with or without a drainage channel.
These wetlands have features such as oxbows, typically associated with floodplains and are
inundated by overspill during a flooding event. This type of wetland consists of a permanently
wet riverine zone, a seasonally or temporary inundated grassland zone and/or standing
water in typical floodplain features such as oxbows, and back swamps. The oxbows and
back swamps are only connected to the river system during a flooding event (Kotze et al
2005, Palmer et al, Ward & Lambie 1999, Rogers 1995).
3.4.2 Seepage
Seepage wetlands occur where groundwater emerges, generally at faults or joints in the
underlaying geology, or at the junction of a permeable layer on an impermeable layer. The
soil is normally saturated and can contain peat. It is very difficult to quantify the nutrient
removal function of the seepage wetlands. The groundwater flow should be measured, as
well as the diversity of nutrients in the groundwater, as a starting point to quantify the nutrient
removal. In addition, there is a lack of information on the evaporative losses from seeps. The
seeps may also receive contaminated runoff during a rainfall event. The portions of nutrients
originating from the different sources are difficult to determine (Palmer et al 2002, Deocampo
1997).
Springs and seeps can be seasonal, permanent, diffuse or point source. These wetlands can
basically be divided into two groups based on the geohydrology, namely confined and
unconfined. The groundwater of unconfined wetlands occurs mostly close to the surface and
the hydrolic conduit is unconfined. In confined wetlands the groundwater is normally deep
underground and is forced to the surface by some pressure, e.g. heat. The hydrolic conduits
are confined by the presence of relatively impermeable layers. Most of the seeps are
unconfined and seasonal, whereas springs are confined and seasonal or permanent. The
aerial extent of seeps is regulated by the landform setting and the volume of discharged
water (Palmer et al 2002, Deocampo 1997).
Seeps contain both vertical and horizontal flow, while vertical flow is more significant for
confined springs. In an unconfined seep the soil is saturated and horizontal surface flow is
taking place (Palmer et al 2002).
Wetland Database for UORC - 31 -