minutes for the Meeting on 28 August 2013.
CAPE Estuaries Programme: Implementation of the Estuary Management Plan (EMP) for the Zandvlei Estuary,
Muizenberg, Cape Town.
Minutes of the 8th Meeting of the Zandvlei Estuary Management Forum (ZEMF): 18:00,
29th May, 2013, Zandvlei Sports Club/Yacht Club. ZEMF 9 Minutes ver A
of follow-up actions.
|DEA & DP to follow up on the question of reporting of sewage spills.
||Shehaam Brinkhuis, Gunther Frantz
|Follow-up with BMB re the process to obtain funding to support the Forum.
|Telephone list on Contingency Plan to be amended, and then whole
document to be circulated to ZEMF Members.
|| Dalton Gibbs
|| September, 2013
|Weekly harvesting reports.
|Initiation of monitoring of siltation at the mouth.
|| September, 2013
|Contact Piet Huisinga to attend next Forum Meeting.
|| Sandra Fowkes
|| September, 2013
1. Welcome and introductions
Participants were welcomed to the meeting by Sandra Fowkes, the Chair of the Forum. A list of participants can be found at Annex 1 and a copy of the Agenda at Annex 2.
Apologies were received from Councillor D’Alton, Garnet Prince, Muzzamiel Gamieldien, Phumla Ketani-Poort, Andrew Taylor, Arne Purves, Damian Gibbs and Josh Gericke.
At the request of the Chair, participants then introduced themselves, and identified issues of concern relating to ZEMF and Zandvlei. The following issues were raised:
- Fragmentation and loss of momentum of the Forum (KF);
- Siltation both at the mouth and the upper reaches of the estuary (GL);
- Siltation – suggested using a grab truck or flushing to alleviate the problem (CV);
- Siltation caused by the influent rivers and water quality (JF);
- Pondweed and sediments (PdV);
- The lack of consensus on the way forward w.r.t. some management measures and thus a delay in updating of the EMP (LJ);
- Mouth management and implications of the proposed removal of the weir (MT);
- Impacts of the weir and pondweed management (DG);
- Eutrophication (DW);
- Sewage spills and pollution (SB & GF – DEADP);
- Clarity on the role of ZEMF; re-energising momentum; active monitoring of City implementation of EMP (SF).
2. Adoption of the Minutes of the 8th ZEMF Meeting
The minutes were adopted without any changes although it was requested that in future the date of the meeting be included in the footer. Adoption was proposed by DW, seconded by GL.
3. Matters arising from the Minutes of the 8th ZEMF Meeting
3.1 Sewage Spills
At ZEMF 6 it had been agreed that a meeting and site visit would be arranged with officials from DEA & DP and the Water and Sanitation Department of the CoCT. SB and GF of DEA & DP reported that they had not met with Water & Sanitation but had had telephonic contact with them and had been advised that there had been only one incident at the sewage works. They had subsequently been sent the results of sampling following this incident which suggested that ammonia levels did not comply, but that E.coli levels were within limits.
Members of the Forum advised that the spills of concern were not from the sewage works itself, but from pump stations and reticulation in the vicinity of Zandvlei itself. Moreover, there had in fact been numerous spills, the most recent being on the previous Friday (23rd August). JF reported that there had recently been a series of small spills in the Rutter Road area. SF also reported that there were a number of anecdotal reports of people getting sick after swimming in the estuary although to date no medical reports have been made available. One of the biggest concerns, therefore, is the failure of Water & Sanitation to report these spills to the Forum – or even the BMB – so that users can be advised against swimming in the vicinity.
During the following discussion, a number of points/proposals were made:
- There are also concerns about the fact that the polluter pays principle is not being applied in that the BMB often has to deal with the consequences of such spills.
- A suggestion was made that following a significant spill, the mouth should be opened to flush the system. However, there were countering views to this proposal.
- It was suggested that Water and Sanitation be requested to attend a future meeting of the Forum to review the past 5 years and advise on their plans for the next 5 (plans to reduce sewage spills). It was important to get all Departments with responsibilities pertaining to Zandvlei to attend meetings.
- It was proposed that an sms network be established to facilitate the reporting of spills to the recreational users.
3.2 Financial support for the Forum
Since it seems the Forum will either become the Advisory Committee in terms of the Protected Area Act – or a sub-committee of such a body – future funding should be made available through the BMB. DG indicated that this could happen in the near future, despite the delays in the proclamation process.
3.3 Health incidents related to recreational use of the estuary
The Chair reported that although there were a number of anecdotal incidents of health problems related to swimming – or other contact – in the estuary, it had not been possible to get medical reports. Moreover, although the Sea Cadets swim in the vlei on a weekly basis, there had been no reported cases of ill health in over a year.
3.4 Legal Action at Zeekoevlei
Damian Gibbs – who had undertaken to follow up on this – was not present at the meeting. However, MT and DG indicated that although there had been legal action related to the leaking of sewage into Zeekoevlei some 35 years ago, as far as they were aware, there was no current action. The previous action had resulted in the installation of a cutoff drain which prevented sewage leaks from reaching the vlei.
3.5 Status of Contingency Plan
DG reported that he had circulated the Contingency Plan to all the affected line functions, but had not had any response. However, he had also spoken to Gregg Oelofse, who is writing the City’s Coastal Policy. This policy will incorporate a number of emergency response plans – including the Zandvlei CP – and the whole package will then be submitted to the Council for approval. In the interim, the CP should be circulated to ZEMF members.
3.6 Follow up on letter to Mr.Asmal re Pondweed
This has not been done as yet.
3.7 Delay in proclamation of City Reserves
It has emerged that the submission of the request to the Premier’s office for the proclamation of some 15 City Nature Reserves has, in fact, not been made as yet. This is due to the fact the Title Deeds of some of the erven involved have not been located. A service provider has now been appointed to complete this work, and it is anticipated that the submission will be made in the next few months.
3.8 TOR for PAAC
DG confirmed that the TOR which had been circulated for discussion at ZEMF 8 had been drafted by the City.
4. Pondweed Management
Ken Findlay reported that the TWG had not been reconvened as he felt that it would be more productive to discuss the comments made on the TWG Recommendations at ZEMF 8 (which he had not been able to attend), at this meeting. He also felt that the recommendations – and the comments thereon – should be made taking into consideration recent developments, namely the fact that the weed harvester has been out of commission for the past two months and that it seems unlikely that these issues would be resolved in the near future, if at all. The schedule proposed in the recommendations is, therefore, not achievable.
KF also felt that pondweed management in Zeekoevlei needs to be approached in a more holistic way i.e. it should also look at the cause/s of the excessive growth – such as nutrient levels. In addition, a different management approach needs to be found for Little Princess Vlei (different machine or biocontrols for Parrot’s Feather), so that the 2nd machine can be released and returned to Zandvlei.
Other issues affecting the success of management measures are:
- The IYC wants to extend the sailing period which would require deeper cutting to accommodate the reduced water levels;
- Coral worm which has recently been shown to have increased significantly over the past 20 years;
- There have been increasing demands for clearing within the Marina;
- There has been inadequate advance notice of recreational events in the estuary. Advance planning is required to align recreational events with mouth management and harvesting schedules.
With respect to the causes of pondweed growth, DW suggested that although there is a need to address nutrient levels, it is unlikely that, given the urban setting of the estuary, they would ever be removed as a factor. Pondweed is, in fact, harvested at many locations world-wide. One of the interesting things that has emerged during his investigations, is that it was shown at Swartvlei that at the end of the growth period (Feb/March), there is usually a huge die-back of pondweed resulting in a significant release of nutrients into the water. Heavy harvesting at the end of the growth period can reduce this release of nutrients by 75% (provided the cut material is removed from the water). The TWG recommendations should take this into account and should advise against harvesting during the early growing season (Nov/Dec), and heavy harvesting in Feb/March.
Regarding coral worm, LJ indicated that it might be possible to get some funding through SANBI to undertake a study on coral worm management and perhaps even the implementation of measures as a case study.
PdV indicated that it is not the Forum’s responsibility to get involved in the day-to-day logistical operations of the Reserve. The TWG/Forum should make its recommendations on Pondweed Management, and it is then up to the City to find a way to implement those recommendations.
The comments on the draft TWG recommendations were then reviewed and KF agreed to revise the document within the next week.
KF also indicated that due to work pressure he was resigning as Chair of the TWG on Pondweed.
5. Any Other Business
5.1 Mouth management/siltation
The paper by Andy Killick as well as personal observations of a number of Forum Members make it clear that the siltation of the estuary – both at the mouth and in its upper reaches – is a major cause for concern in relation to the long-term sustainability of the system. Siltation at the mouth (behind the weir) has resulted in the formation of large shallow sand-banks which are gradually moving upstream and, amongst others, restricting the movement of fish. While this is not a new issue, there has been a failure to agree on a way forward on the matter, largely because of the complexity of the issue. Removing the weir, for example – which is the preferred option from a strictly ecological viewpoint – would have serious implications for the Marina infrastructure, and would result in the undercutting of the caissons which stabilise the channel near the mouth. Dredging, or digging out the channel on a regular basis would be prohibitively expensive and would impact the benthic ecology. It would also trigger a requirement for an EIA.
It was therefore suggested that:
- monitoring of the sediments should be undertaken as soon as possible so that hard data on the sediment build-up is generated. MT agreed to organise this; and
- Piet Huisinga – previously from CSIR – be invited to give a presentation to ZEMF reviewing outcomes of previous studies and outlining feasible options.
5.2 Vlei By-law
DG reported that the Vlei By-law has now been completely rewritten as the Recreational Water-use by-law in which activities are designated as:
Provision is also made for the appointment of Wardens.
The draft by-law will now go through a 2-step stakeholder consultation process:
- Stakeholder engagement around the various water bodies (i.e. users of specific water-bodies); and
- General public comment.
The stakeholder meetings for Zandvlei are likely to take place in October.
It was agreed to postpone the AGM to February
6. Dates and focus for next meeting/s
The next Forum meeting was scheduled for Monday 28th October at 18:00 depending on the availability of Piet Huisinga.
List of Attendees at the 9th Meeting of the
ZEMF on 28th August 2013.
||Pierre de Villiers
|| Dalton Gibbs
|| John Fowkes
|Peninsula Canoe Club
|Cape Bird Club
|| Gavin Lawson
|C & EC
|| Lynn Jackson
CAPE Estuaries Programme: Facilitation of the Estuary Management Plan (EMP) for the Zandvlei Estuary,
Muizenberg, Cape Town
9th Meeting of the Zandvlei Estuary Management Forum (ZEMF)
13:30 – 16:00 : 28th August, 2013
Zandvlei Sports Club (Yacht Club)
1. Welcome and introductions, apologies etc
2. Adoption of Minutes of ZEMF 8
3. Matters arising from the 8th ZEMF Meeting 3.1 Meeting on sewage spills
(LJ) 3.2 Proposal on financial support for Secretariat function (SF) 3.3 Health incidents & recreational activity in the vlei (SF)3.4 Legal action at Zeekoevlei re sewage spills
(DaG) 3.5 Status of contingency plan (DG) 3.6 Follow up on letter to Mr Asmal re pondweed
(SF) 3.7 Clarification of delay in declaration of City Reserves under PAA (PdV)
3.8 Origin of TOR for PAAC (SF)
4. Pondweed Management 4.1 Review of comments on recommendations of the Pondweed TWG (as made at ZEMF 8)
(KF) 4.2 Other Pondweed-related matters
5. Silting up of Zandvlei MouthDiscussion around article by Andy Killick
6. Any Other Business AGM
7. Dates and focus for next meetings in 2013.
Final Report of the ZEMF Pondweed Technical Working Group (TWG) on Pondweed Management for Comment (30 Aug 2013)
The pondweed, Potamogeton pectinatus, occurs naturally in Zandvlei and is an important component of the ecosystem, providing habitat for a variety of organisms, reducing nutrient loading and oxygenating the water. However, as a result of the high nutrient conditions, pondweed has been a problem in Zandvlei for many years, at times forming dense mats which restrict boating activities, exacerbate flooding, limiting light penetration, restricting current flow and thus increasing stagnation, and, when they start to decompose, causing unpleasant odours and raising nutrient levels. The pondweed in Zandvlei has therefore been managed since 1976 by harvesting it using a mechanical harvester and such mechanical harvesting of pondweed is an accepted practice around the world. Although the harvesting has been successful at times, there have been occasions when over-harvesting has led to collapses in the population (Harding, 1999) while at other times the excessive levels of pondweed have hindered recreational use of the estuary, created nuisance conditions and impacted on property values in the area. This situation continues despite the development of harvesting guidelines for the City by Southern Waters in 1999.
2. Protocol for Pondweed Management
The TWG therefore recommends that a new protocol for the management of pondweed in Zandvlei be developed based on the following:
2.1. Desired outcomes of pondweed management
Given the ecological importance of pondweed, the overall objective of management efforts must be to achieve a sustainable level of pondweed in the system while at the same time preventing the development of conditions which affect the recreational use of the estuary, are a nuisance to residents or affect property values in the area. In other words, the pondweed levels must be sufficient to maintain the ecosystem services it normally provides (including habitat provision, oxygenation and nutrient sink services).
In addition to its ecological functions, Zandvlei has significant aesthetic and recreational value and is the primary attraction for the majority of residents in the area. It is used for formal and informal recreational activities - including inter alia bird-watching, picnicking, yachting, canoeing, boardsailing, kite-boarding and swimming - as well as a number of events such as the Rotary annual Dragonboat racing fundraiser, Scout regattas and annual Kontiki event, and has recently been used by international canoeing teams for training purposes.
It thus has a variety of socio-economic benefits for the area and needs to be managed accordingly. This includes keeping specified areas clear of pondweed, other nuisance plants and debris which tends to accumulate in some areas, especially the blind canals of the Marina. It should be noted that pondweed management treats the system symptomatically only in that the causal factors of the extensive pondweed growth (the elevated nutrient loads within the system arising from its location within an urban setting) are not addressed within this plan.
The specific proposed outcomes of pondweed management therefore include:
- The areas set aside for recreational activities (see Figure 1) to be kept clear of pondweed to a depth of 0.5m for all canals in the Marina, and to as deep as possible in the main body of the vlei. As the weed harvester can only cut to a depth of about one meter (such cutting is very slow) the cutting schedule in the main vlei should be synchronised with the mouth opening schedule so that maximal depth cutting can be carried out when the water depth is at its shallowest.
- A healthy pondweed reserve of 30% of the estuary area (see Figure 1) should be maintained;
- An improved understanding of pondweed dynamics in Zandvlei.
- The ensuring of adequate flow regimes within the system so that stagnation (and nutrient build-up in localised areas) does not occur.
- It should be noted that the harvesting of pondweed can act as an important nutrient sink. Pondweed senesces at the end of summer, dying back and releasing nutrients to the water column. It is important that timing of harvesting considers the growth of the pondweed biomass (and the resultant stripping of the water column of nutrients) and that the biomass is removed as solid plant matter before the senescence occurs.
2.2. Achieving the Outcomes
The harvesting guidelines developed in 1999 by Southern Waters recommended a harvesting frequency of 12 times a year in the recreational areas. Refinement of this frequency could be determined through a monitoring programme, which given the inter-annual variation in pondweed growth should be carried out as a multi-year programme. Such monitoring needs to consider the senescence and release of nutrients back to the water column.
Two proposed models for the management of pondweed in the Zandvlei system were discussed by the TWG, including a “Rotational Schedule” as previously maintained and an “On Request” model. The TWG identified that both models had advantages and disadvantages and proposed that a combination of these two models would be the best strategy. The Rotational Schedule model proposes that pondweed be harvested on a strict rotational schedule aimed at ensuring that a) pondweed biomass does not get out of control and b) acute management intervention be required when it does so. The “On Request” model proposes that pondweed be harvested on a stakeholder request basis to address the criteria of water flow, ecological function and recreational needs. For example, under this model recreational users may apply for clearing of particular areas, but such applications need to be made as far in advance of particular events as possible. Clearing should however be carried out close to the required dates to ensure that no re-growth has occurred.
The merging of these two models resulted in the following combined management model.
- During the period that harvesting was undertaken by City Parks, harvesting was carried out 7 times annually (twice in Summer, twice in Autumn, once in Winter and twice in Spring). This approach is generally regarded as having been successful for those periods when these targets were met (i.e. when the harvester was able to complete the required work). For at least the next year, all the areas to be harvested for recreational or ecological requirements, should be cut 7 times. This harvesting should be implemented according to a reasonably strict rotational schedule and should be monitored so as to be able to assess the effectiveness of these proposals and to provide a basis for any future adjustments;
- 20% of the pondweed reserve should be harvested once during the course of each year. Such harvesting should be carefully monitored;
- A strict and extensive harvesting schedule needs to be implemented at the start of the senescence at the end of summer. It should be noted that such harvesting is aimed at bulk removal of nutrients from the system and the removal of cut material needs to be ensured.
- Clearing within 2m from the banks should be limited to securing access to the central channel and must be undertaken by residents. Requests from residents to use the harvester to cut pondweed within this area should not be entertained;
- Projects on the monitoring and assessment of pondweed harvesting and growth should be undertaken in collaboration with CPUT. In particular the following data may be useful
- Weekly photographic monitoring from selected vantage sites such as Boyes Drive could provide an important source of long-term information.
- The number of harvested loads by area within the system
- An initial review of the frequency of coots within the monthly / quarterly CWAK counts may provide some historic data as proxy for pondweed biomass.
- Stakeholders may apply for clearing of particular areas, but such applications need to be made as far in advance of particular events as possible to allow for adequate planning. However, cutting should however be carried out close to the required dates to ensure that no re-growth has occurred.
2.3. Challenges of these management models
2.3.1. Harvesting Demand and Supply
Based on the map in Figure 1, approximately 61.5 ha of Zandvlei (recreational areas including the Marina canals) need to be cut 7 times per year. In addition, 20% of the pondweed reserve area should be cut once a year. This means that a total of 436.1 ha need to be cut/year. Assuming a cutting rate of 0.14ha/hour (Southern Waters), 3115 machine hours/year are required to complete the schedule. In addition, provision needs to be made for maintenance and downtime as a result of weather conditions and machine failure. Based on records for the past year, the average number of operational hours achieved by the harvesting machine per day was between 5 and 6 – for periods when the machine was actually functional. However, these records also indicate a 20% downtime. On this basis, and assuming a 5-day week, the current complement of 1 harvesting machine and a single driver/operator delivers less than half of the hours required to complete the schedule. Realistically then, the only option available to meet the required schedule is to:
A. Make a second machine and driver available. The second weed harvester was transferred by City Parks to Little Princess Vlei in with little consultation to Zandvlei users. It is recommended that the rationale for this transfer of this resource be reviewed including:
- The size, extent and biomass of invasive aquatic plant material in the Little Princess Vlei system (where the majority of material is believed to be “Parrot’s feather”)
- The efficacy of cutting “Parrot’s feather” with the transferred weed harvester. It is believed that the transferred machine is not optimal for this system.
- The use of the Little Princess Vlei system as a recreational facility including its comparable value to Zandvlei as a training facility for sporting disciplines at an international level,
B review of the purchase agreement of the harvester as it possibly may have been originally purchased for the Marina da Gama.
C. have a relief driver so that harvesting is not affected by driver illness and, when necessary, can be extended into weekends or after hours (should the weather be conducive);
D. reduce downtime by improving maintenance and addressing other operational issues.
2.4. Cutting Operational Management Strategy
In order to overcome the above challenges it is recommended that:
- The second machine should be returned to Zandvlei on a permanent basis as each transfer costs R60 000 return in terms of a crane and special flatbed trailer;
- The current Zandvlei machine has been re-engineered and maintained to the required specifications; however, the City could consider the holding of critical spares to reduce downtime;
- A GPS should be installed on the machine to monitor the time and locations at which the harvester is operating;
- Additional resources should be provided to Biodiversity Management so that additional drivers can be trained with a view to increasing the efficiency of machine utilisation (increased number of hours/day) and prevent downtime as a result of illness;
- The possibility of utilising barges to transport cut material from the harvester to the shore should be investigated with a view to increasing the time available for cutting. Such barges should be designed to be able to collect floating rafts of cut weed when these occur;
- Proper provision must be made to ensure that harvested material is removed from the banks of the estuary on a timeous basis.
- A Robust framework for monitoring and analyses of the efficacy of the harvesting schedule needs to be in place.
Figure 1. The proposed clearing of pondweed for recreational requirements.
List of Commonly Used Acronyms
|| Biodiversity Management Branch
|| City of Cape Town
|| Cape Peninsula University of Technology
||Co-ordinated Waterbird Annual Census
|DEA & DP
||Department of Environment Affairs and Development Planning
||Estuary Management Plan
||Imperial Yacht Club
||National Environmental Management: Protected Areas Act
||Protected Area Advisory Committee
||Provincial Coastal Committee
||South African Police Services
||Technical Working Group
|W & S
|| Water and Sanitation Department
||Zandvlei Estuary Management Forum