The progress report was presented by Bernelle at the bimonthly ZPAAC meeting on 15 March 2017. Bernelle attended the Estuary Management workshop which fortuitously used Zandvlei as case study.
Management of Estuaries in South Africa Short Learning Course Programme
6 – 8 March 2017, Krommee Rhee (Stellenbosch)
Basic layout of the course:
- Value, structure and function of estuaries Anusha Rajkaran (UWC)
- Boundaries of estuaries & mouth management plans Lara Van Niekerk (CSIR)
- Key threats affecting estuaries Janine Adams (NMMU)
- Fisheries & compliance Stephen Lamberth (DAFF)
- Estuary legislation including ecological water requirements of estuaries Susan Taljaard (CSIR)
Site visit on Day 2: Zandvlei!
- Management of Zandvlei by the City of Cape Town Joshua Gericke
- Water quality monitoring and management at Zandvlei Candice Haskins
- Estuary Management Protocol and progress with EMPs (legal & institutional overview) Vuyo Madlokazi (DEA)
- Experiences with implementation of estuary management plans in the Western Cape including funding models Pierre De Villiers (CapeNature)
- Guidelines for the development of EMPs: Situation Assessment, Objective Setting Phase – Implementation Phase – Identification and prioritization of management actions. Lara van Niekerk (CSIR)
- Western Cape government estuary management framework Marlene Laros (Western Cape)
Impressions at the course:
- Many links for my work (http://indiebio.co.za/interfaces)
- Site visit was Zandvlei!
- DropBox with many, many resources: https://www.dropbox.com/sh/x9c854uhuls2l0r/AAAUSnt3eVttQV9B1Ph5NRzfa?dl=0
- People were very impressed by Zandvlei – kudos Josh and community!
“It has been amazing to see how the manually intensive mouth management has been working. The amount of political will and community effort has been amazing.”
“Generally the prognosis for any urban system is it’s going downwards, it’s generally only a question of how fast. To see how well Zandvlei is doing is testament to the energy of the people involved and the support of the other departments in the municipality.“ – Lara van Niekerk, CSIR
- Conversations with Josh: Thrilled to see that the dreams have been thought through – the stage is set, and ready to go! Support is there. Now to sweat the details.
Interesting aerial images of Zandvlei:
And an image from the 1920’s is apparently in existance, but it is not referenced (?) (taken at a skew angle by a low flying aircraft). From these images it is clear that Zandvlei has been a highly modified system for a really long time, reinforcing the approach that this system cannot be managed as, or even attempted to be returned to, a natural system.
Key historic changes -> Dream Zandvlei
Joshua presented the key historic changes that has affected the vlei, and these are the same things that are included in the Dream Zandvlei projects:
Increased nutrient input -> reduce nutrient input at source (incl. (waste)water biorefineries
Hardened catchment -> soften catchment, water sensitive design (including things like permeable pavement)
Rivers canalised -> meandering, absorptive rivers for flood amelioration and ecosystems services
Marina da Gama partially developed (ex-salt marsh) -> how to better have human settlements along the water’s edge, in the 5m contour line estuary functional zone?
Riverbanks hardened and reshaped -> Riverbanks integrated into estuary to contribute to water quality improvement, flood management and bird and fish habitat.
Marina da Gama and estuary dredged -> responsible, responsive sediment management – integrating mouth management and reduction of sediment inflow.
Mouth laterally constrained -> improved intertidal habitat (see Barry Clark notes)
Weir and mouth manipulation -> Keep the mouth as open as possible, even more dynamic mouth management (see Barry Clark notes)
Westlake wetlands rehabilitation – contributing to lowering the nutrient inflow, flood management and sediment reduction.
Dredging: not a straightforward story
- Stratification is an undesired possibility, due to the more dense (heavier) sea water taking up the deeper channels.
- Prawn population is a concern if everything is dredged all at once, that doesn’t give the prawn time to relocate.
- Slow, steady may work – Need more research, talk to Port Owen (Bergriver)
- Law on hazardous waste? If the dredgings is hazardous it may be a legal problem – investigating this.
- Conclusion: dredging is an option, but possibly better to look at other ways to influence flow and sediment removal.
- People involved: Bernelle, Neil Armitage, Mike (PenCC), Barry Clark
Litter traps – separate at source
- Design from Josh:
- Recycling, separation at source: meetings pending with Verigreen and Tuffy
- People involved: Gavin Lawson, Peter , Sharon McCallum, Brian Gaze, Bernelle Verster
Sport: Paddle run series
- Planned dates: monthly, May – Aug. Currently securing event permits.
- Water quality? Complies for intermediate contact recreational use (<1000 coliforms/100mL over 12 month period): not swimming or diving (or has some risk), but complies well for activities like sailing or paddling.
- People involved: Jon Adams, Damian Gibbs, Quiver guy, Bernelle, Caitlyn
(Report from Candice Haskins during Estuary Monitoring Workshop)
- We have concentrations, we need flow and depth metering (from conversations with Josh)
- Average of 0.12 (mg/L?) P for Zandvlei over 4 years
- “Monitoring at Zandvlei, Marina da Gama and Westlake Wetland has been consolidated so that monthly samples are now analysed for bacterial, chemical and algal constituents at each of nine locations. “
- NESMP long term monitoring programme, permanent probes: Aqua TROLL 200, hourly reading of temp, salinity, conductivity. Data download & maintenance monthly.
Boat based Aquaread hand held instrument. (O2, salinity, temp, conductivity, pH) (incoming neap tide, monthly)
- People involved: Bernelle, John Faulkes, university students…
Monitoring point descriptions
(From water quality report by Candice Haskins)
- ZAV1: North of Zandvlei
- ZAV2: Opposite the yacht club
- ZAV5: Outlet channel
- CR01: Westlake River at the crossing of the Main Rd adjacent to Chenel Rd
- CR06: Spaanschemat River
- CR16: Middle reaches of the Diep River
- CR20: Keysers River at the Military Road crossing (CR20)
- CR21: Confluence of Sand Canal and Langevlei Canal just before their combined entry to Zandvlei
- CR22: Confluence of the Westlake and Keysers River (near the railway crossing)
- DRRSC: Diep River flows into the southern portion of Little Princessvlei
- LPV S: Southern portion of Little Princessvlei in the region where the Diep River canal enters the water body
- LPV N: Northern section of the vlei
Reedbeds at Pollsmoor
To be a failsafe when sewage overflows, to manage the outflow while maintenance is addressing the challenge. Also to be a buffer against upstream shocks. Taskteam formed, haven’t met yet.
- People involved: Bernelle, Eugene Moll (Candice Haskins, Sam Braid)
Westlake wetlands rehabilitation
- These is support for this, and the meandering function to return. After the litter traps, this is the highest priority intervention.
Feedback from Source to Sea meeting (Sarah Chippendale)
- Need a way to invest, run as an NGO
- Multi-use zones – e.g. cycling
- Next step: lobby for cycling paths in catchment.
- Many schools along the rivers.
From the Dreaming Zandvlei conversations, it became apparent development of the following is needed:
- Communicate what a catchment is, how it links to Zandvlei – include in marketing material
- Citizen scientists (better word for citizens?) – volunteer salinity monitoring currently exists.
- Spend one day a week in Josh’s office, formulate the business plan, detailed project plans.
- The will is there! Just need the time.
- Acknowledge the different priorities and focus
- E.g. Josh’s reserve management priority, sports priority, commercial, education, etc.
- Project plan:
- Detailed work plan (which action by whom)
- Staff and financial resource plan
- Monitoring plan – resource health and compliance (impact and performance)
- Help write the integrated plan, how all the plans fit together.
- Wetland priority.
- Speak to Kevin Winter about flow meters
- Pilot the litter trap in Sandriver: Need to find someone to do the pilot study (student at UCT?)
General notes from the ZPAAC meeting
- The rivers need help.
- What are the critical information for the priority management actions?
(Martin Thompson knew all the flow rates – Abdullah Parker (Justin) should have this)
- Typha reeds are taking over… manual removal is not good enough. Need something like a front end? We’re losing the battle! This is a potential flood risk!
- We are starting to pick up increasing salinity in the lower end. May impact typha growth?
- Rebuilding the “13 mile bridge”
- Traditionally: Telco, use a long arm digger. But challenged.
- It actually just needs to get burnt. But in urban area! – CAN WE LOBBY FOR THIS?!
- The function of the reedbed is to trap silt and nutrient. Need to think about how to get to those sediments and nutrients out.
- What happens if we have a spring high followed by a cold front?
- Need to function as flood overflow, that surges can overflow into the reedbeds. “Surge bed”
- Huge berm that can be removed.
- Reedbed priority:
- First priority was mouth management – we have done as much as we can in the short term.
- Wetland is next priority. So we need to get available resources and act on it. Need to breach roads, once at Keysers, twice at Westlake.
- Burning is not the critical step to do this.