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