The hydrogeomorphic ( HGM ) classification system classifies wetlands according to : - Form ( geomorphic characteristics ); and - The way in which water moves in , through , and from the wetland system ( hydro characteristics ).
The HGM classification recognises five generic palustrine |
wetland types : |
1 . |
Pans and depressions , including lakes ; |
2 . |
Seepage wetlands ; |
3 . |
Unchannelled valley bottoms ; |
4 . |
Channelled valley bottoms ; and |
5 . |
Floodplains . |
Need for regulatory lines
The potential for conflict starts around the need for developers to use maximum space , which may / does encroach into wetlands , flood plains , and estuarine supratidal areas .
Therefore , the need for regulatory lines includes , but is not confined to :
• Changing to higher flood lines ; keeping tracts of lands and aquatic ecosystems intact ; and maintaining economic and ecological functions .
• 11 % loss of wetlands ( tidal ) by 2100 ( Theron and Rossouw , 2008 ).
• Maintaining economic and ecological functions ( policy , land developers , and municipalities must work together to achieve a balance ).
• Open space is required between infrastructure and the shoreline of rivers / wetlands , the sea and / or other sensitive habitats .
• Identifying environments at risk .
• Developments focused around environmental attributes : slope , water , accessibility , and aesthetics .
So , why are wetlands important and what are their functions ? 1 . Water purification : traps sediments ; retains excess nutrients ; retains excess heavy metals ; floating , submerged and rooted emergent plants .
2 . Flood control and protection : holds back excess water ; recharges groundwater due to sponge capacity ; prevents erosion — submerged , rooted emergent and wet terrestrial plants ( narrow leaved , broad leaved and floating leaved ).
3 . Shoreline stability and protection : protection against erosive wave and high flow action ; plants decrease energy of high flow waters ; roots of plants bind soils : rooted , emergent plants ( narrow leaved and broad leaved ) and wet terrestrial plants .
4 . Water recycling ( including groundwater recharge and stream flow maintenance ): recharge of groundwater and surface water ; a source of water downstream ; transpiration recycles groundwater and surface water ; and prevents evaporation — all aquatic and wetland plants . 5 . Biodiversity support : serves as a home to a wide range of unique plants and animal life ; provides nesting material , habitat , and a food source .
6 . Economic benefits : adds to eco-tourism , that is , bird watching , hiking , camping , fishing and photographic excursions .
The ecological role of plants are bank and soil stabilisers ; water quality and cycling ; food retention ; species diversity support ; parasitic ( plants that are parasitic on other plants ); insectivorous ( plants that use other sources for nutrients ); and invader ( plants that are known to be noxious invader species ).
The workshop group visited the Colbyn Wetland Nature Reserve to see the theory in practice . The reserve is managed by the City of Tshwane and extends over 80 hectares , adjoining the Pretoria suburbs of Colbyn , Kilner Park , and Hatfield and it is located 5km from the Pretoria CBD . The reserve forms a green corridor as a refuge and migration route for wildlife . The Hartbeesspruit flows through the Coldbyn Wetland . The reserve consists of a wetland , peatland , and grassland , as well as the relatively unspoilt vegetation of the neighbouring rocky ridges . Peatland occupies just over a hectare of the total wetland area , estimated to be about 7 000 years old , and is 2.4m thick at its deepest point , with an average thickness of 1.5m .
Now perhaps we can appreciate the importance of wetlands , especially when considering building / infrastructure developments , and include them in the planning process , rather than trying to ‘ steal ’ from their area .
Illustration extracted from the paper Restoration , creation , and recovery of wetlands , wetland functions , values , and assessment .
Acknowledgements
• Ernst Wohlitz ( City of Tshwane )
• Dr Carin van Ginkel ( Cripsis Environment )
• Department of Water and Sanitation
• SANBI
• Water Research Commission
• Department of Environmental Affairs . u
Wetland functions , and internal and external values . networking contributor tech news industry environment infrastructure municipalities
Water Sewage & Effluent March / April 2017 25