RIVER MANAGEMENT PROGRAM

Transcription

1 RIVER MANAGEMENT PROGRAM FOR THE MAINTENANCE OF THE BANKS OF THE SMALBLAAR RIVER ON FARM 417/2, RAWSONVILLE, WORCESTER Prepared for: Deetlefs Family Trust FEBRUARY 2011 Prepared by: Boland Environmental Consultants CC PO Box 250, Worcester, 6849 Tel / Fax work@bolandenviro.co.za BolandEnviro CC 2011 All rights reserved 1

2 CONTENTS 1. BACKGROUND LOCATION AND SITE DESCRIPTION RELEVANT ACTIVITIES ACTIVITIES ASSOCIATED WITH RIVER DEGRADATION, EROSION AND FLOODING: PROPOSED RIVER MAINTENANCE ON FARM 417/2, WORCESTER: POTENTIAL DETRIMENTAL IMPACTS ASSOCIATED WITH THE MANAGEMENT ACTIONS: RIVER MANAGEMENT PROGRAM PROPOSED MITIGATION MEASURES EFFECTIVENESS OF THE MANAGEMENT ACTIONS ANNEXURES ANNEXURE A LOCALITY MAP ANNEXURE B SITE LAYOUT ANNEXURE C ENVIRONMENTAL AUTHORIZATION

3 1. BACKGROUND This River Management Program provides an operational framework with regards to the ongoing maintenance/repair of the banks of the Smalblaar River, on Farm 417/2, Worcester, hereafter referred to as the Property. Large scale quarrying of rock from within the Smalblaar River channel, downstream of the Property, appears to have destabilized the river bank to the point where active measures are needed to stabilize the banks and prevent erosion and damage to the Property during heavy rains and flooding. Maintenance work along the banks of the Smalblaar River is required on a regular basis to prevent the formation of bottlenecks (blockages within the river channel) and subsequent flooding and erosion and to prevent the periodically need for repair of resultant damage to vineyards and infrastructure. The National Environmental Management Act (Act 107 of 1998) (NEMA) makes provision for the identification and assessment of activities that are potentially detrimental to the environment and which require authorization from the relevant authorities based on the findings of an environmental impact assessment (EIA). According to the regulations of Section 24(5) of NEMA (EIA Regulations 2010), authorisation is required for the following listed activity related to the proposed river maintenance work on Farm 417/2, Worcester: Government Notice R546 of 2010, listed activities: 18 The infilling or depositing of any material of more than 5 cubic metres into, or the dredging, excavation, removal or moving of soil, sand, shells, shell grit, pebbles or rock from (i) a watercourse; (ii) the sea; (iii) the seashore; (iv) the littoral active zone, an estuary or a distance of 100 metres inland of the high-water mark of the sea or an estuary, whichever distance is the greaterbut excluding where such infilling, depositing, dredging, excavation, removal or moving is for maintenance purposes undertaken in accordance with a management plan agreed to by the relevant environmental authority; or occurs behind the development setback line. This EMP is required to conform to conditions as set out in the Acknowledgement of Receipt of the latest Application Form for Basic Assessment, issued by the Department of Environmental Affairs and Development Planning s (DEA&DP) on the 1st of October The EMP has been drafted taking into account the Western Cape Provincial Guideline for Environmental Management Plans (2005). The scope and the level of 3

4 detail have been adjusted to an appropriately restricted level, reflecting the following considerations: The assessment of impacts Mitigation & monitoring requirements Legal requirements The complexity of the project activities A key outcome of the EMP is that clear environmental objectives and supporting procedures need to be defined that specifically address those aspects of the proposed works and their maintenance which may have a significant detrimental effect on the environment. 2. LOCATION AND SITE DESCRIPTION The Subject Land is part of Farm 417 Portion 2, Worcester and is located in the Breede Valley Municipal area, 18 km south-west of Worcester and approximately 1 km south-west of Rawsonville. The Property, also known as Deetlefs Wine Estate, is owned by the Deetlefs Family Trust, hereafter referred to as the Landowner. The Property is situated adjacent to the Smalblaar River which flows in a north-eastern direction towards Rawsonville. The size of the Property is ha in extent while most of the property is under cultivation with vineyards (103 ha). Maintenance is required over an estimated 3.5 kilometres of the Smalblaar River along the southeastern border of the Property. The river bed along the subjected section of the Smalblaar River consists mostly of large boulders and pebbles while some sections consist of sand. The northern bank of the river (section where maintenance is required) is flanked entirely by vineyards from Deetlefs Estate. The lower section of the southern bank is flanked by vineyards on neighbouring farms (Farm 418/46, 421/RE and 697/RE). The upper section of the south-eastern bank, situated on the foothill of the Dutoits Mountain, also forms part of Deetlefs Estate and comprise natural Brandvlei Waboomveld vegetation (Cape Fine-Scale Project, Integrated Vegetation Layer) which is considered least threatened. This area, however, includes a large patch, directly adjacent to the river, that is severely infested with alien black wattle trees (Acacia mearnsii). This part of the Property is currently not under cultivation and there is currently no direct access to this site (will require access across the Smalblaar River). The Smalblaar River and riverine corridor (buffer area) is identified as an aquatic critical biodiversity area (CBA) by the CAPE Fine-Scale Project. CBAs represent the smallest geographical configuration of terrestrial and aquatic sites or features that are needed to maintain biodiversity pattern and ecological 4

5 processes while reducing risks of conflict with other land uses. The biodiversity management objectives for CBAs are to maintain natural land in a natural state, to rehabilitate degraded areas to a natural or near-natural state and to prevent further degradation. 3. RELEVANT ACTIVITIES Important note: This River Management Program provides an operational framework with regards to the ongoing maintenance along the banks of the Smalblaar River and does not make provision for typical construction, operational and decommissioning phases. Due to the un-predictive nature of riverine systems (water flow, flooding and the need for post-flood emergency repairs), limited detail is available regarding the temporal and spatial aspects of the specific management actions Activities associated with river degradation, erosion and flooding: Any activity which takes place in a river, especially with heavy machinery, has the potential to change the flow of water in a river. Other impacts include the destruction of habitat, river channel modification, river bed modification and riparian zone destruction. The removal of riparian plants leads to bank instability and provide a niche for the establishments of alien invasive plant species. Typically impacts to agri-riparian systems in the Western Cape associated with degradation of the riparian environment, flooding and erosion (King 2009) include: cultivation of alluvial soils in the floodplain channelisation of rivers bulldozing of naturally deposited sediments to open rivers using spoil (natural alluvium and/or clean builder rubble) to construct levees to protect crops from floods and invasion by alien woody plants within the riparian zone Activities that potentially cause river degradation, flooding and erosion along the subjected section of the Smalblaar River include large scale quarrying of rock from within the river channel down stream of the Property, cultivation along the entire subjected section of the river (restricting channel width) and extensive invasion by alien Acacia mearnsii (black wattle) within the river corridor and adjacent natural areas which further restricts the channel width and contributes to bank destabilisation. 5

6 3.2. Proposed river maintenance on Farm 417/2, Worcester: Maintenance activities along the subjected section of the Smalblaar River on Farm 417/2, Worcester aim at the protection of the riparian zone and the removal of bottlenecks or blockages which may impede on the water flow and may cause flooding and associated river bank erosion. Due to un-predictive aspects such as water flow, flooding and the need for post-flood emergency repair, limited detail is available regarding the temporal and spatial aspects of the specific management actions. Potential activities include: Protection and maintenance of the river corridor (buffer area) to prevent further degradation of the riparian zone. Removal of blockages caused by vegetation debris from the river channel. Opening of areas where deposited sediments cause bottlenecks within the river channel (using machinery where necessary). Removal and control of alien vegetation. Natural rehabilitation and stabilization of the river bank. Post flood emergency repairs. Permanent river protection works, such as the installation of fixed structures (gabions & groynes) is not considered as this stage. These activities may trigger additional listed activities in terms of the NEMA EIA Regulations The natural stabilization and protection of the river banks is considered as a primary permanent solution. Once a holistic River Management Program is in place for the entire Smalblaar River, the Landowner will become involved with the program and apply the applicable river management practices. The Landowner has already put much effort in stabilizing and protecting the banks of the Smalblaar River by encouraging Prionium serratum (Palmiet) to establish where the banks of the Smalblaar River is exposed. It is the Landowners intention to continuo with these practices Potential impacts associated with the management actions: Access across the Smalblaar River to clear alien trees (physical alteration to river bank) Disturbance and/or removal of indigenous riparian vegetation by machinery Soil erosion due to disturbances Decline in water quality (turbidity) Alien invasion into newly opened areas Further destabilisation of the river bank and degradation of the riparian zone 6

7 4. RIVER MANAGEMENT PROGRAM The overall goal for ongoing maintenance along this section of the Smalblaar River on Farm 417/2, Worcester is to undertake management practices in a way that will: Ensure that activities are properly managed in respect of environmental aspects and impacts. Reduce the risk of future flooding and erosion. Prevent damage to vineyards and infrastructure. Prevent further degradation of the Smalblaar River corridor which falls within an aquatic CBA. Initiate and encourage the natural stabilisation and rehabilitation of the river banks PROPOSED MITIGATION MEASURES Objective: Protection of the Smalblaar River corridor Whenever possible, maintenance activities should be planned to avoid unnecessary disturbance to the river corridor. Mitigation: Action/control A riverine / ecological buffer area must be respected and maintained between the edge of the Smalblaar River and existing vineyards on the Property. This buffer area must be at least 32 m where the riparian zone is currently undeveloped. Should the clearing of additional areas on the Property for new vineyards be authorized, it should allow for a minimum buffer of 40 meters between the rivers edge and new vineyards. This buffer may include an unsurfaced farm track to a maximum width of 6 meters, providing for a minimum of 34 meters undisturbed buffer. No further development may take place within the riverine corridor. No waste, building rubble or wine pressings may be dumped in the river channel or riparian zone. No permanent roads, bridges or structures may be permitted across the Smalblaar River. Objective: Access across the Smalblaar River Access across the Smalblaar River is undesirable. However, should this be required, such access must be properly managed. Mitigation: Action/control Vehicular access across the Smalblaar River should be prevented as far as possible. 7

8 No permanent roads or structures may be permitted across the Smalblaar River. Should such access be required, it must be limited to temporary access during the lowest flow of Smalblaar River (summer months). Access should also be restricted to one site where it will cause least disturbance i.e. where the water is shallowest, where the channel is narrowest and where indigenous riparian vegetation will not be disturbed. Stands of Prionium serratum (palmiet) on the river bank should not be disturbed in any way (by crossing the river) as these plants play an essential role in stabilising the river bank. The banks of the river should be stabilized (packed stones) at the access points to prevent soil erosion and the river bed should be protected with loosely packed stones obtained from the immediate vicinity (no construction is envisaged). Objective: Removal of debris or driftwood blockages in the river channel Where debris and driftwood result in blockages that may be a potential risk for backwater build-up and flooding, removal of such blockages from the river channel is desirable. Mitigation: Action/control Removal of blockages must be conducted by hand wherever possible. Use of machinery should only be as a last resort. All debris or driftwood must be removed and properly disposed off. No dumping of debris or driftwood should be allowed in the riparian zone (river channel and buffer areas). Objective: Opening of bottlenecks caused by deposited sediments Modifying long stretches of the river channel is not desirable. Un-impacted reaches of rivers with refugia (hiding places) are a critical component of natural river ecosystems and play an important role in maintaining biodiversity. Mitigation: Action/control Minimise the spatial extent of disturbance Maintain physical diversity (habitat diversity such as pools and riffles) where it exists, or create it where it has been removed by management actions. The frequency of maintenance activities within specific sites should be considered to enhance recovery (i.e. prevent too frequent repetition of site-specific activities). Control timing of maintenance activities (prevent work immediately prior to high flows or floods). Spoil material must not be dumped on riparian or bank habitats. Spoil material should preferably be removed from the buffer area or used to fill erosion sites elsewhere along the river bank. 8

9 Cleared areas (where vegetation has been damaged or removed by earthmoving machinery) should be re-vegetated with natural riparian vegetation. Limit the use of earthmoving machinery within the river channel. Manual labour (wheelbarrow and shovels) should always be considered first and used wherever possible. Machinery should be checked for oil and fuel leaks before and after earthmoving in the riparian zone. Objective: Control alien vegetation Alien black wattle trees (Acacia mearnsii) is a major problem within the Smalblaar river and adjacent natural areas. These plants use a lot of water, restricts the channel width and tend to block up river systems and contributes to bank destabilisation. Alien vegetation can become a major problem in disturbed/open areas caused by management actions. Mitigation: Action/control Eradicate all alien black wattle trees from the Smalblaar River, as well as the riverine buffer areas. Implement measures to remove and control alien trees in adjacent natural areas in the medium to long-term. Debris of cleared alien trees should be removed from the site. No dumping of wood debris should be allowed within adjacent natural areas or within the riparian zone. Monitor newly opened areas for the establishment of alien vegetation. Re-vegetate cleared or disturbed areas with natural riparian vegetation. Ongoing, annual alien clearing (follow-up control) should be implemented Objective: Rehabilitation and natural stabilization of the river bank and buffer area Although restoration to pre-disturbed condition is often nearly impossible, the safe-guarding or increasing of the range of habitats along a section of the river would improve diversity in plant and animal components. Mitigation: Action/control Any erosion sites should be repaired as soon as possible. All foreign material currently within the riparian zone that can be removed i.e. building rubble, garden refuse and winery byproduct / waste, should be removed as soon as possible. No herbicide spraying should take place within the riverine buffer, except in the case of control of Pennisetum clandestinum (kikuyu grass), where only focus herbicide (kikuyu specific) should be used. Re-vegetation the riverine buffer area with suitable locally indigenous riverine species, to supplement what is already there. 9

10 Essential species that can be planted include Calopsis paniculata, Psoralea aphylla (bloukeur), Diospyros glabra (vliebos, kraaibessie), Virgilia oroboides (keurboom), Rhus angustifolia (smalblaar; the river is probably named after this species), Metrosideros angustifolia (also known as smalblaar), Brachylaena neriifolia (waterwitels), Ilex mitis (Cape holly), Merxmuellera cincta (vleigras), Willdenowia incurvata (zonkwasriet), Dodonaea angustifolia (sandolien, ysterbos), and Brabejum stellatifolium (wild almond; Van Riebeeck s hedge). It is important that each is planted in suitable microhabitat some species are dependant on groundwater access, others prefer drier sites. Prionum serratum (palmiet) should be encouraged to establish along the edge of the river. Plantlets must be propagates from existing individuals and planted along the edge of the river to stabilise the banks. Restore physical (habitat) diversity along the river banks. All visible alien plants should be removed annually. The bio-physical environment of different section along the Smalblaar River will have site specific management implications. The following schema should be used for defining and describing specific environmental features for specific work sites. This information must be used as a guideline in the implementation of the proposed mitigation measures and site specific management actions: Hydrophysical environment Physical flow of water River bed Banks Riffles and rapids Unbroken Pools Sand Gravel Cobbles Rock Soil Peat Clay Cobbles Natural bush Condition of the bank and land-use Palmiet Alien Plants Field Infrastructure Cliffs (Source: Proposed Framework for the Second Phase of the Langtou River Project, C. de Villiers 2010) High flow Low flow 10

11 4.2. Effectiveness, risks and assumptions of the management actions The implementation of this River Management Program and the proposed actions on Farm 417/2, Worcester, along the identified sections of the Smalblaar River, should not negatively impact the downstream aquatic or botanical environments. This management plan aims to conserve the river corridor and eradicate alien invasive plants. Up-steam sources of alien vegetation as well as down-stream river practices may however impede on the management goals. A holistic River Management Program for the entire Smalblaar River will be more effective, as all properties along the river will be engaged in the development of the plan and proposed management actions. This management plan could form a preliminary foundation of the formulation of a broader River Management Program. The mitigation actions proposed in this River Management Program are based on general river management practices. Due to the un-predictive nature of riverine systems (flood events and not knowing where or when blockages or bottlenecks may form) limited detail is available regarding the temporal and spatial aspects of the specific management actions. More information may be required prior to the implementation of site specific actions. It is recommended that an ecologist be appointed to establish the status quo of the river ecosystem along the identified sections of the river (to identify and map distinctive environmental features). The ecologist should also ideally be available during the implementation of management actions to provide further input. 5. ANNEXURES Annexure A Locality map Annexure B Site layout Annexure C Environmental Authorization (when issued) 11

12 Annexure A Locality map Farm 417/2 Figure A1. Locality map of the area surrounding Farm 417/2 (Groot Eiland), Worcester (sourced from Government topo-cadastral map 3319) Farm 417/2 Figure A2. Locality map showing the boundary of Farm 2/417 and the surrounding area (sourced from 1: Government topo-cadastral maps 3319CB) 12

13 Annexure B Site layout 13

14 Deetlefs Wine Cellar Area severely infested with black wattle Figure B1. Proposed section of the Smalblaar River, between red markings, where ongoing maintenance is required. 14

15 B C A Figure B2. Map showing the boundary of Deetlefs Estate. Continuous maintenance has to be performed between Point A B, on the banks along the Smalblaar River. This section gets damaged (flooding and erosion) yearly with winter rains. A bottleneck (blockage) that caused extensive flooding was removed in 2009 (Point C). Future maintenance are required to prevent such blockages and subsequent flooding and erosion. 15

16 Annexure C Environmental Authorization (when issued) 16