Appendix K11 - GCS€¦ · 1.2 Site Description 1 2 WETLAND DELINEATION 3 2.1 Introduction 3 2.2 Legislation 4 2.3 Wetland Assessment 8 2.3.1 Methodology 8 2.3.2 Southern Site 8 2.3.2.1

Appendix K11 Wetland Delineation Report

INVESTEC

Proposed Corobrick North & South Mixed-use Development, Avoca, Ethekwini Municipality

Wetland Delineation Report

Date : 30 September 2012 Revision No. : 1 Project No. : 11706

SPECIALIST REPORT DETAILS

This report has been prepared as per the requirements of Section 32 of GNR 543 - Environmental Impact Assessment Regulations and the National Environmental Management Act (Act 107 of 1998)

Report prepared by: ……Greg Mullins…Pr.Sci.Nat.………………..

Expertise / Field of Study: … Ecologist ……………..

I, …Greg Mullins……. declare that this report has been prepared independently of any influence or prejudice as may be specified by the Department of Agriculture, Environmental Affairs and Rural Development.

Signed:………… …………………… Date:……30/ 09/ 2012…………

Date: 30th September 2012

Document Title: Corobrick North & South Mixed-use Development – Wetland Delineation Report

Author: Greg Mullins Pr.Sci.Nat.

Revision Number: 2

Checked by: Dr R Kinvig Pr.Sci.Nat.

Approved: Dr R.Kinvig Pr.Sci.Nat.

Signature:

For: Investec

PROPOSED COROBRICK NORTH & SOUTH MIXED-USED DEVELOPMENT, AVOCA, ETHEKWINI MUNICIPALITY

WETLAND DELINEATION REPORT

Contents Page

1 INTRODUCTION 1

1.1 Terms of Reference 1

1.2 Site Description 1

2 WETLAND DELINEATION 3

2.1 Introduction 3

2.2 Legislation 4

2.3 Wetland Assessment 8

2.3.1 Methodology 8

2.3.2 Southern Site 8

2.3.2.1 Wetland Unit 1 & 2 – Remnant Valley Head Wetlands 8

2.3.2.1.1 Landscape setting 8

2.3.2.1.2 Soil and Geology 8

2.3.2.1.3 Hydromorphic Conditions 8

2.3.2.1.4 Vegetation Composition 9

2.3.2.2 Wetland Unit 3 – Hillslope Seepage Wetland 9





2.3.2.3 Wetland Unit 4 – Hillslope Seepage Wetland 9





2.3.3 Northern Site 11

2.3.4 System 1 – Valley Bottom Wetland (Western system) 11





2.3.5 System 2 – Valley Bottom Wetland (Central system) 11





2.3.6 System 3 – Valley Bottom Wetland (Eastern system) 12





2.3.7 Umhlangane River Tributary 14

2.3.7.1 Landscape setting 14

2.3.7.2 Soil and Geology 14

2.3.7.3 Hydromorphic Conditions 14

2.3.7.4 Vegetation Composition 14

2.4 Wetland Impact Identification and Mitigation 15

2.4.1 Impacts to the Umhlangane Tributary 15

2.4.2 Direct Habitat Loss 15

2.4.3 Erosion and Stormwater Runoff 15

2.4.4 Pollution of systems and downstream habitat 15

3 CONCLUSION 16

Tables

Table 1: Relationship between degree of wetness (wetland zone), soil-physio-chemistry and vegetation (after Kotze et al, 1994)

Figures

Figure 1: Project Site with features and landmarks.

Figure 2: Cross section through a wetland, indicating how the soil wetness and vegetation indicators change along a gradient of decreasing wetness. (Reproduced from Kotze (1996), DWAF Guidelines).

Figure 3: Wetland mapping across proposed development site -. South

Figure 4: Wetland mapping across proposed development site - North.

INVESTEC prepared by: SiVEST Environmental Division 11706 – Corobrick North / South Mixed-use Development – Wetland Delineation Assessment Revision No. 1 30th September 2012 Page 1

PROPOSED COROBRICK NORTH & SOUTH MIXED-USED DEVELOPMENT, AVOCA, ETHEKWINI MUNICIPALITY

WETLAND DELINEATION REPORT

1 INTRODUCTION

SiVEST Environmental Division was appointed by Investec to carry out a Wetland Delineation of the proposed Corobrick North and South development sites as part of the initial planning and environmental authorisation process for the property.

1.1 Terms of Reference

SiVEST was required to carry out the following scope of work during this investigation:

Identify and delineate any surface water and wetland areas falling within the proposed development areas; and

Identify potential impacts that may arise from any development or associated infrastructure.

1.2 Site Description

The proposed development site comprises the main land holding currently forming part of the development planning process. The joint property is approximately 330 Ha in extent and consists of two approximately equal sized parcels of land separated by North Coast Rd.

The eastern edge of the site is defined by the N2 freeway. The western boundary is the R102. To the north is the Kindlewood Residential Estate. The southern edge of the site is the Piesang River and M25 (Fig 1).

The northern site is characterised by three sub catchments (including the Glen Anil Stream) that drain south west into the Umhlangane River. Hills and ridges on this portion are generally steep-sided and orientated in a north east / south west alignment. The majority of the northern site is planted to sugar cane. Those areas not farmed are currently being mined by Corobrick for clay and shale. Two areas of alien plant dominated forest exist on the south eastern corner of the property.

The southern site is dominated by the Corobrick brick factory, storage yards and management head office. The facility is located on the flat portion of the site adjacent to the confluence of the Umhlangane with the main trunk system. The topography of this portion is characterised by a single large ridge line running along the eastern edge of the site. The land slopes westward towards the floodplain and river. The upper portions of the slope are planted to sugarcane while the lower portions have been extensively mined and altered through years of brick making on site.

An extensive network of dirt tracks and farm roads traverses the sites. A number of these roads cross the Umhlangane tributary via concrete bridges. The wetland systems on the southern portion have been extensively modified as a result of the mining on site. Those systems on the north have been impacted but remain largely intact from a geomorphic and hydrological perspective.



2 WETLAND DELINEATION

2.1 Introduction

Wetlands are defined as those areas that have water on the surface or within the root zone for long enough periods through the year to allow for the development of anaerobic conditions. These conditions create unique soil conditions (hydric soils) and support vegetation adapted to these flood conditions.

In terms of Section 1 of the National Water Act (Act 36 of 1998), wetlands are legally defined as:

(1)…land which is transitional between terrestrial and aquatic systems where the water table is usually at or near the surface, or the land is periodically covered with shallow water, and which land in normal circumstances supports or would support vegetation typically adapted to life in saturated soil.

Hydric soils develop a grey or sometimes greenish or blue-grey colour, as a result of the chemical reduction of iron (gleying). Hydric soils that are seasonally flooded are characterised by the formation of mottles, which are relatively insoluble, enabling them to remain in the soil long after it has been drained. Consequently it is possible to identify wetland areas on the basis of soil colour, using a standard colour chart, as matrix hue and chroma decrease, while mottle hue and chroma initially increase and then decrease the more saturated the soils become (Table 1).

Table 1: Relationship between degree of wetness (wetland zone), soil-physio-chemistry and vegetation (after Kotze et al, 1994)

Degree of wetness

Temporary Seasonal Permanent / Semi-permanent

Soil Depth (0cm –10cm)

Matrix chroma: 1-3 Few / no mottles Low / intermediate OM Non-sulphuric

Matrix chroma: 0-2 Many mottles Intermediate OM Seldom sulphuric

Matrix chroma: 0-1 Few / no mottles High OM Often sulphuric

Soil Depth (40cm – 50cm)

Few / many mottles Matrix chroma: 0-2

Many mottles Matrix chroma: 0-2

No / few mottles Matrix chroma: 0-1

Vegetation Predominantly grass species

Predominantly sedges and grasses

Predominantly reeds and sedges

Vegetation distribution within wetlands is very closely linked to the flooding regime. Terrestrial plants are not tolerant of flooding within the root zone for periods long enough to cause anaerobic conditions, and are thus found on higher ground. The distribution of wetland plants is related to their tolerance of different flooding conditions, and their distribution within a system can be used as an indication of the wetness of an area.

Typically, indicators of soil wetness based on soil morphology correspond closely with vegetation distribution, since hydrology affects soils and vegetation in systematic and predictable ways. However, in systems where the hydrological regime has been modified due to human activities, vegetation distribution will not vary systematically with soil morphology. The response of vegetation to alteration of hydrological conditions is rapid (months/years), whereas the response of soil morphology to such alteration is slow (centuries). Therefore, lowering of the water table or reduction of surface flows, may lead to rapid establishment of terrestrial vegetation, whereas the soil morphology will retain indicators of wetness for a lengthy period.

Soil morphology forms the basis of wetland delineation nationally, following international protocols, mainly because it provides a long-term indication of the “natural” hydrological regime. However, soil morphology cannot be considered to necessarily reflect the current hydrological conditions of the site where the hydrological regime has been altered, and in such circumstances vegetation provides the best indication of the distribution of wetlands as it best reflects current hydrological conditions.


Figure 1: Cross section through a wetland, indicating how the soil wetness and vegetation indicators change along a gradient of decreasing wetness, from the middle to the edge of the wetland. (Reproduced from Kotze (1996), DWAF Guidelines)

Wetlands are known to perform a number of important functions within ecosystems. These include flood attenuation, sediment trapping, improving water quality and being areas of rich biodiversity. The disturbance or loss of wetlands has been directly linked with numerous natural disasters and species loss, both within South Africa and globally. What is important to note is that, should one of these wetland functions be greatly affected, this does not necessarily mean that other functions are not still intact. In other words should the flood attenuation function of a wetland have been greatly reduced through the cutting of vegetation across the site, this does not necessarily mean that the wetlands ability to purify water has also been lost. In many cases, obviously dependent on the degree and nature of disturbance, wetlands still maintain some degree of functionality.

2.2 Legislation

The protection and correct management of wetlands is entrenched in a number of places within South African Law. The following is an indication of the relevant legislation pertaining to development and wetlands and is by no means a full legal review.

The Constitution of the Republic of South Africa (108 of 1996)

The legal source for environmental law in South Africa is the Constitution of the Republic of South Africa (108 of 1996). The Constitution fundamentally altered the legal environment in South Africa and all laws must be interpreted within the context of the Constitution. After the Constitution the National Environmental Management Act (107 of 1998) and the Environmental Conservation Act (73 of 1989) are the most important pieces of Environmental Legislation. Under the Constitution greater emphasis has been given to improving the social environment. The Bill of Rights is fundamental to the Constitution of the Republic of South Africa, and in Section 24 states that:

Everyone has the right (a) to an environment that is not harmful to their health or well-being; and (b) to have the environment protected, for the benefit of present and future generations through reasonable legislative and other measures that (i) prevent pollution and ecological degradation; (ii)

Terrestrial Some erosion No baseflow No residual pools Terrestrial plants No mottles No wetland vegetation

Temporarily waterlogged Yellow-brown soils Few mottles Mixture of Terrestrial and

wetland plants Some Wetland Vegetation Intermittent baseflow

Seasonally waterlogged Mixture of wetland and

terrestrial grasses Significant wetland vegetation

(Hydrophilic grasses and sedges)

Deposition of Coarse material Seasonal Base Flow Often Residual Pools Grey soils Many mottles

Permanently waterlogged Significant Wetland Vegetation (Sedges, reeds, Bulrushes) Permanent Base Flow Permanent Inundation Grey soils Few mottles


promote conservation; and (iii) secure ecologically sustainable development and use of natural resources while promoting justifiable economic and social development.

National Environmental Management Act (107 of 1998)

NEMA is South Africa’s overarching environmental legislation and has, as its primary objective to provide for co-operative governance by establishing principles for decision making on matters affecting the environment, institutions that will promote co-operative governance and procedures for co-ordinating environmental functions exercised by organs of state and to provide for matters connected therewith (Government Gazette, 1998).

The Act provides for the right to an environment that is not harmful to the health and well being of South African citizens; the equitable distribution of natural resources, sustainable development, environmental protection and the formulation of environmental management frameworks. In addition there is recognition that development must be socially, environmentally and economically sustainable and that the disturbance of ecosystems and loss of biological diversity are avoided, or, where they cannot be altogether avoided, are minimised and remedied (Government Gazette, 1998).

Section 30 (1, 3 and 4) of the NEMA states that:

(1) (a) ‘‘incident’’ means an unexpected sudden occurrence, including a major emission, fire or explosion leading to serious danger to the public or potentially serious pollution of or detriment to the environment, whether immediate or delayed. (b) ‘‘responsible person’’ includes any person who; (i) is responsible for the incident; (ii) owns any hazardous (as listed in SABS 0228) substance involved in the incident; or (iii) was in control of any hazardous substance involved in the incident at the time of the incident; (3) The responsible person or, where the incident occurred in the course of that person’s employment, his or her employer must forthwith after knowledge of the incident, report through the most effective means reasonably available (a) the nature of the incident; (b) any risks posed by the incident to public health, safety and property; (c) the toxicity of substances or by-products released by the incident; and (d) any steps that should be taken in order to avoid or minimise the effects of the incident on public health and the environment to; (i) the Director-General; (ii) the South African Police Services and the relevant fire prevention service; (iii) the relevant provincial head of department or municipality; and (iv) all persons whose health may be affected by the incident.

(4) The responsible person or, where the incident occurred in the course of that person’s employment, his or her employer, must, as soon as reasonably practicable after knowledge of the incident; (a) take all reasonable measures to contain and minimise the effects of the incident, including its effects on the environment and any risks posed by the incident to the health, safety and property of persons; (b) undertake clean-up procedures; (c) remedy the effects of the incident; (d) assess the immediate and long-term effects of the incident on the environment and public health.

The National Environmental Management Act (107 of 1998) extends legal liability beyond simply the person directly responsible for environmental degradation. In terms of the Act the land owner, his representatives and the person responsible for the environmental degradation will be liable for any costs of remediation if any construction were to take place within the Permanent / Semi-permanent and Seasonal boundary.

NEMA also governs the Environmental Impact Assessment process and the list of activities deemed, under the Act, to require either a Basic Assessment or a full Environmental Impact Study. According to Government Notice 544, 545 and 546 issued in terms of Section 24 of NEMA (Act 107 of 1998), a number listed activities directly or indirectly link to planning of development in and around wetlands and riparian areas.

National Water Act (36 of 1998) According to Section 2 of the National Water Act (36 of 1998), the purpose of the Act is to ensure that the countries water resources are protected in a sustainable and equitable manner for the benefit of all South Africans.

(2) The purpose of this Act is to ensure that the nation’s water resources are protected, used, developed, conserved, managed and controlled in ways which take into account amongst other


factors; (a) Meeting the basic human needs of present and future generations; (b) Promoting equitable access to water; (c) Redressing the results of past racial and gender discrimination; (d) Promoting the efficient, sustainable and beneficial use of water in the public interest; (e) Facilitating social and economic development; (f) Providing for growing demand for water use; (g) Protecting aquatic and associated ecosystems and their biological diversity; (h) Reducing and preventing pollution and degradation of water resources; (i) Meeting international obligations; (j) Promoting dam safety; (k) Managing floods and droughts and for achieving this purpose, to establish suitable institutions and to ensure that they have appropriate community, racial and gender representation.

Thus as the Public trustee (Section 3 (1)) it is National Governments responsibility, through the Minister of Water Affairs and Forestry, to ensure that water use is in the public interest (Section 2 (d)), aquatic ecosystems and biodiversity are protected (Section 2 (g)), and there is a reduction and prevention of pollution and degradation to water resources (Section 2 (h)).

In terms of Section 1 (xxiv) of the Act, a watercourse is defined as:

(xxiv)``watercourse’’ means -

a) a river or spring; b) a natural channel in which water flows regularly or intermittently; c) a wetland, lake or dam into which, or from which, water flows; d) and any collection of water which the Minister may, by notice in the Gazette, declare to be a

watercourse, and a reference to a watercourse includes, where relevant, its bed and banks.

Thus the development or modification of wetlands in any form falls is governed by the conditions stipulated in Chapter 4, Part 1 of the Act which sets out general principles for regulating water use.

Water use is defined broadly, and includes taking and storing water, activities which reduce stream flow, waste discharges and disposals, controlled activities (activities which impact detrimentally on a water resource), altering a watercourse, removing water found underground for certain purposes, and recreation. In general a water use must be licensed unless it is listed in Schedule I, is an existing lawful use, is permissible under a general authorisation, or if a responsible authority waives the need for a licence.

21. For the purposes of this Act, water use includes –

a) taking water from a water resource; b) storing water; c) impeding or diverting the flow of water in a watercourse; d) engaging in a stream flow reduction activity contemplated in section 36; e) engaging in a controlled activity identified as such in section 37(1) or declared under section

38(1); f) discharging waste or water containing waste into a water resource through a pipe, canal,

sewer, sea outfall or other conduit; g) disposing of waste in a manner which may detrimentally impact on a water resource; h) disposing in any manner of water which contains waste from, or which has been heated in,

any industrial or power generation process; i) altering the bed, banks, course or characteristics of a watercourse; j) removing, discharging or disposing of water found underground if it is necessary for the

efficient continuation of an activity or for the safety of people; and k) using water for recreational purposes. 22. (1) A person may only use water –

a) without a licence –

a if that water use is permissible under Schedule 1; b if that water use is permissible as a continuation of an existing lawful use; or c if that water use is permissible in terms of a general authorisation issued under section 39;

b) if the water use is authorised by a licence under this Act; or


c ) if the responsible authority has dispensed with a licence requirement under subsection (3).

As development or modification of watercourses / wetlands is not included in Schedule 1, a license is required to carry out any activity involving a wetland.

In terms of Section 1 (xv) of the Act, pollution is defined as:

(xv) … the direct or indirect alteration of the physical, chemical or biological properties of a water resource…

It is broadly recognised that wetlands are beneficial in terms of stream flow regulation, flood attenuation and water purification. Any construction activity that takes place within a wetland may be considered to be an activity that is potentially harmful to both aquatic and non-aquatic organisms and generally reduce local water quality.

Part 4 of the National Water Act (36 of 1998), deals with pollution prevention, and in particular the situation where pollution of a water resource occurs or might occur as a result of activities on land. The person who owns, controls, occupies or uses the land in question is responsible for taking appropriate measures to prevent pollution of water resources and if these measures are not taken, the catchment management agency concerned may itself do whatever is necessary to prevent the pollution or to remedy its effects, and to recover all reasonable costs from the persons responsible for the pollution.

In terms of Section 19 (1 and 2) of the National Water Act (36 of 1998);

(19) (1) An owner of land, a person in control of land or a person who occupies or uses the land on which

(a) Any activity or process is or was performed or undertaken; or;

(b) Any other situation exists, which causes, has caused or is likely to cause pollution of a water resource, must take all reasonable measures to prevent any such pollution from occurring, continuing or recurring.

(2) The measures referred to in subsection (1) may include measures to –

(a) Cease, modify or control any act or process causing the pollution; (b) Comply with any prescribed waste standard or management practice; (c) Contain or prevent the movement of pollutants; (d) Eliminate any source of the pollution, (e) Remedy the effects of the pollution; and (f) Remedy the effects of any disturbance to the bed and banks of a watercourse.

Conservation of Agricultural Resources Act (43 of 1983)

The aim of CARA is to provide for control over the utilisation of the natural agricultural resources within South Africa and to promote the conservation of soil and water resources, indigenous vegetation and the control of invasive plants.

In terms of Section 3 of the Act, soil conservation works are defined as;

(1)…work which is constructed on land for – (a) The prevention of erosion or the conservation of land which is subject to erosion; (b) The conservation of improvement of the vegetation or the surface of the soil; (c) The drainage of superfluous surface or subterranean water; (d) The conservation or reclamation of any water source, or; (e) The preventing of the silting of dams and the pollution of water…

The Act goes on to state in Section 12, that;

(12) (1) (a) A soil conservation work shall, except where otherwise provided in this Act or a scheme, be maintained by every land user of the land concerned and his successor in title at his own


expense in a manner, which, in the opinion of the executive officer, will ensure the continued efficiency thereof…

Thus in terms of the Act the land owner or land user is responsible for the maintenance of all soil conservation works located on his property. As already discussed, it is broadly recognised that wetlands provide a number if valuable functions, including, stream flow regulation, flood attenuation and water purification. Consequently the maintenance and improvement of the structure and function of wetlands furthers the aims of the Conservation of Agricultural Resources Act (43 of 1983).

In order to achieve the aims of CARA the Minister of Agriculture may prescribe control measures which are to be complied with by all land users, and include;

(6)…(e) The utilisation and protection of vleis, marshes, water sponges, water courses and water sources.

2.3 Wetland Assessment

2.3.1 Methodology

Sampling was carried out across the proposed development site. At each sample point, soil was sampled at 0-10cm and 40-50cm. The value and chroma were recorded for each sample, as well as the degree of mottling. Vegetation sampling was carried out in a 5m radius surrounding each of the sample sites.

Mapping of the wetland was carried out using ArcGIS 9 and was based on the field data collected. Soil and vegetation change indicated the interface between wetland and non-wetlands. These boundaries were then extrapolated to follow local contours, but also took into account the hydraulic conductivity of the soils and their effect on drainage.

2.3.2 Southern Site

2.3.2.1 Wetland Unit 1 & 2 – Remnant Valley Head Wetlands

These wetland units have been assessed together as they occupy largely the same landscape unit and more importantly, they have both been impacted in the same way. Historically these wetlands would have drained westwards on to the floodplain of the Umhlangane tributary. The mining activities on the site have effectively removed all of the wetland between the tributary and the mid-slopes of the systems. All that now remains are small areas of wetland in the heads of these systems.

2.3.2.1.1 Landscape setting

The remaining wetland areas lie in the valley heads created by the undulating terrain. The systems are characterised by seepage elements and some valley bottom characteristics before draining into artificial channels created through the mining area.

2.3.2.1.2 Soil and Geology

The systems are characterised by the presence of shallow bedrock and low soil permeability in the lower reaches. This is further supported by the steep incised nature of the valley and the exposed rock faces. The valley heads in which the intact wetlands remain, along the eastern boundary, appear to be sandier in nature (perhaps suggesting the reason why these areas were not mined).

2.3.2.1.3 Hydromorphic Conditions

Runoff from the surrounding slopes is likely to drain rapidly into these systems as a result of the sandier nature of the soils on the catchment head. The generally narrow nature of the systems confines flow through the remnant valley bottoms until the drains. At this point flow is rapidly directed into the Umhlangane tributary. Limited retention can be expected from the sandy catchments. This is reflected in the presence of predominantly temporary wetland characteristics, with minimal seasonal wetland noted.


2.3.2.1.4 Vegetation Composition

Vegetation composition of both systems was entirely sugar cane. No notable indigenous vegetation was identified in the remnant systems.

2.3.2.2 Wetland Unit 3 – Hillslope Seepage Wetland

This small wetland unit lies on the eastern edge of the site and drains in an easterly direction towards the N2 freeway. The wetland is moderately impacted and has been utilised for sugar cane farming for a number of years and maintains a limited biodiversity value.


The system lies on a steep east facing slope within a shallow drainage depression. The system exists largely as an expression of the groundwater movement on the hillside.


The site is characterised by the presence of shallow bedrock and low soil permeability. This is further supported by the steep incised nature of the valley and the exposed rock faces.


The steep topography, shallow rock and thin soil covering of this system results in groundwater flow remaining close to the soil surface as it moves downslope. This is then expressed as hillslope seepage.



2.3.2.3 Wetland Unit 4 – Hillslope Seepage Wetland

This wetland unit lies on the south eastern corner of the site. The system is planted to sugar cane and has a shallow central drain to facilitate rapid removal of unwanted moisture. The system drains in a south easterly direction, into the Umhlangane River.


The system lies in a broad, relatively shallow basin on the lower hillside of the site. The relatively gentle slope has promoted diffuse flows in the system and thus the need to install a drain to allow farming to continue in the system.


The site is characterised by deeper soils than the systems assessed above. Being lower on the slope, colluvial deposition has occurred and resulted in thicker soil profiles. Some bedrock elements were noted surrounding the system, but appear not to influence the system greatly.


The broader, bowl shaped nature of the system and catchment has resulted in slower movement of water through the systems and the development of a wider wetted perimeter. Finer sediments in the colluvial deposits also serve to slow drainage in the system. A linear drain has been dug through the centre of the system to facilitate drainage.





2.3.3 Northern Site

2.3.4 System 1 – Valley Bottom Wetland (Western system)

This wetland lies in a shallow linear depression between the R102 and a steep hillside on the property. It is likely that the road bed historically encroached into a broader system flowing across this portion.


The system lies in a constricted valley bottom drainage line. Gentle topography has resulted in deposition of sediments and the formation of a permanent unchannelled system. The wetland has been impacted through construction of the R102, together with a bridge as part of the internal road network.


The system comprised predominantly of fine sediment deposits. Colluvium and alluvium from the catchment have been carried downslope into the system where, as a result of the change in topography, deposition has occurred. The slope to the east of the system is relatively steep and some underlying rock elements were noted.


The movement of water through the wetland on this portion of the site is predominantly via runoff from higher in the catchment. No doubt some lateral inputs can be expected from the surrounding slopes, but the majority of the hydrological input is from off of the site. The system drains into the Umhlangane tributary.


The system was predominantly permanent in nature. Species identified in the wetland included Phragmites australis, Typha capensis, Cyperus dives, Coix lacryma-jobi, Ludwigia octovalvis, Aneilema aequinoctiale, Imperata cylindrica, Cyperus sphaerospermus and Cynodon dactylon

A number of alien invasive plants were noted within the system. Most notable was an extensive stand of Ipomoea purpurea. In addition stands of Lantana camara, Chromolaena odorata, Arundo donax, Schinus terebinthifolius and Melia azedarach were all noted within or adjacent to the wetland.

2.3.5 System 2 – Valley Bottom Wetland (Central system)

This wetland system lies in a small forked valley. The wetland drains west into the Umhlangane tributary. The site is extensively farmed with clay extraction activities occurring on the surrounding slopes.


The wetland systems lie in relatively broad valley with a gentle westward slope. The natural systems would have been unchannelled wetlands, however artificial drains have subsequently been excavated to facilitate farming reducing the wetted perimeter of the system.


The systems appear to lie largely on sands. Deposition and colluvial movement have created broader valley lines and diffuse flow. The mining of clay in the immediate vicinity of the system suggests that some reduced permeability could exist.


The system is likely to receive hydrological inputs from the surrounding slopes. The deeper sandy soils are likely to provide a more sustained percolation of water into the wetland (versus the shallow


soils on other parts of the site). The slower, diffuse movement of water in the system has resulted in broader more resilient systems than elsewhere on site. The potential for perching of the watertable is also possible given the high incidence of clays on this part of the site.


The majority of the wetland was planted to sugar cane. However portions of the system immediately adjacent to the drains contained indigenous hydrophytic elements. Species identified included Cyperus dives, C. sphaerospermus, Typha capensis, Ludwigia octovalvis, Imperata cylindrica, Cynodon dactylon and Stenotaphrum secundatum. Given the propensity for the entire system to burn as part of the sugar cane harvesting process, alien plant invasion was limited. Some isolated elements of Chromolaena odorata, Lantana camara and Ipomoea purpurea were noted.

2.3.6 System 3 – Valley Bottom Wetland (Eastern system)

This system is linked with a narrow valley bottom element and a portion of riparian habitat linked with the Glen Anil Stream. The wetlands occupy incised valleys and drain from adjacent to and beneath the N2 in a westerly direction before joining the larger Umhlangane tributary.


This small valley bottom / riparian system lies within a series of narrow valley lines. The steep sloping sides of the valley have limited the width of the wetland. Some colluvial deposition was noted. Its likely that the farming practices have promoted some erosion on the surrounding slopes. The Glen Anil Stream occupies a narrow incised channel and the system is believed to function largely as a channelled valley bottom wetland.


The systems appear to lie largely on sands. Deposition and colluvial movement have created broader valley lines and diffuse flow. The mining of clay in the immediate vicinity of the system suggests that some reduced permeability could exist.


Hydrological inputs into the system are via groundwater discharge from the adjacent slopes into both the wetland and stream. Secondly, inputs from the broader catchment of the Glen Anil Stream can be expected too. The system is likely to be prone to high flows during peak storm events.


As above, the majority of the wetland was planted to sugar cane. Areas of the systems were however found to include indigenous hydrophytic elements. Species identified included Phragmites australis, Cyperus sphaerospermus, Typha capensis, Ludwigia octovalvis, Imperata cylindrica, Cynodon dactylon and Stenotaphrum secundatum.

In addition, alien invasive elements were also prevalent. The woody portions of the stream course were dominated by Schinus terebinthifolius. In addition, stands of Lantana camara, Chromolaena odorata and Melia azedarach were also noted.



2.3.7 Umhlangane River Tributary

The Umhlangane River flows just west of the Corobrick site and elements of the floodplain form the western boundary of the site. A tributary of this system flows in an east to west direction across both properties. The tributary roughly bisects the northern site before forming the northern boundary of the southern site immediately adjacent to the R102.

2.3.7.1 Landscape setting

The river meanders across the site. Its course across the northern portion of the property is characterised by steep slopes running directly into the river course, together with some, though limited floodplain elements.

The river has wider floodplain elements on the southern portion of the site, associated with the confluence with the trunk system and the broadening of the catchment. The floodplain has been highly developed on this portion as a result of the Corobrick Complex and subsistence agriculture. The Corobrick site includes large fill platforms that have been extended across large portions of the floodplain to create level areas outside of the flood risk zone.

2.3.7.2 Soil and Geology

The upper steam course has eroded though finer grained colluvial sediments and in areas, minor bedrock elements were exposed. Some deposition was noted in this portion. However erosion appears limited given the well vegetated nature of the upper system.

The southern floodplain is was characterised by a confined steam course as a result of the fill platforms on the southern edge of the stream. Soil structure across this portion shifted from colluvial to alluvial deposits. Typically courser grained sands and silts were found on this area.

2.3.7.3 Hydromorphic Conditions

Inputs into the system are via the broader quaternary catchments of the main tributary, as well as the Glen Anil Stream. In addition, inputs can be expected from the wetland systems and as a result of direct ground and surface water recharge from the surrounding slopes. The tributary is likely to receive significant additional inputs via the municipal stormwater system. This is likely to increase the peak flow volumes and velocities during high rainfall events.

2.3.7.4 Vegetation Composition

The river and floodplain were characterised by a mix of indigenous hydrophytes and a high number of invasive alien species. Indigenous elements included Phragmites australis, Cyperus dives, C. sphaerospermus, Typha capensis, Coix lacryma-jobi, Ludwigia octovalvis, Imperata cylindrica, Cynodon dactylon and Stenotaphrum secundatum.

Alien species included Ipomoea purpurea, Lantana camara, Chromolaena odorata, Schinus terebinthifolius, Arundo donax, Pennisetum purpureum, Melia azedarach, Acacia mearnsii and Solanum mauritianum.


2.4 Wetland Impact Identification and Mitigation

Development of the property is likely to result in impacts to the wetland systems. In the absence of a specific development layout, the following issues have been identified as some of the key impacts likely to face the systems on site.

2.4.1 Impacts to the Umhlangane Tributary

Impact: Development of the sites in close proximity to the Umhlangane Tributary has the potential to further impact on this system and affect onsite and downstream habitat integrity.

Mitigation: All proposed development must be suitably setback from the main tributary and the feeder streams. System buffers should allow for the establishment of a functional corridor along the riparian corridor. Management and enhancement of these areas should be a priority within the development.

In this regard it is important to note that the Umhlanagne catchment is currently being used as a flagship system within the Ethekwini Municipality’s Climate Change Adaptation Program. It is advisable that the relevant departments are engaged within the City regarding anything planned within the catchment

2.4.2 Direct Habitat Loss

Impact: Development of the site may result in encroachment or the loss of wetland habitat on the property.

Mitigation: In order to limit the loss of wetland on the property the generally accepted mitigation hierarchy must be followed for the assessment and planning of development. Impacts should be avoided – mitigated and finally offset, in that order. Development of the site should look to not impact or influence the systems in a negative way. Where this is not possible the impact should be quantified and mitigation proposed to reduce the scale of the negative impact. The remaining or residual impact that is not possible to be mitigated must then be offset.

2.4.3 Erosion and Stormwater Runoff

Impact: Increased hardened surfaces and modification to the catchments on site could result in a significant alteration to the runoff and drainage patterns on the property. .

Mitigation: The development of a comprehensive Stormwater Management Plan is critical in avoiding negative impacts associated with the development. Runoff generated must be locally attenuated and carefully released into the surrounding systems in a manor close to the current status quo. Systems should be put in place to allow diffuse infiltration closer to source rather than piping to attenuation pond and point release of flows. Mitigation must include management of envisaged impacts for both the wetland and riparian systems on site.

2.4.4 Pollution of systems and downstream habitat

Impact: Typically industrial development results in increased risk of contamination and water pollution given the nature of the land use and the increased runoff. Spills or leaching of materials stored on site could entre local watercourses and have negative impacts on the fauna and flora of these systems

Mitigation: The design of the top-structures on the sites must take cognisance of this risk and the stormwater management systems for these sites must be designed in such a way that potentially contaminated runoff from risk areas drains to sewer, whereas runoff from areas considered generally ‘cleaner’ can be directed into the stormwater systems. By separating the ‘gray’ and ‘black’ runoff, the risk of pollution can be notably reduced.


3 CONCLUSION

The wetland and riparian assessment of the site identified the presence of a number of systems. The integrity of these habitats ranged from largely intact to highly modified. Current and historic land uses have had significant impacts on the integrity and functioning of the wetlands and riparian areas on the site. It is likely that without careful and correct planning development of the site will result in further degradation of the systems on site. Mitigation steps must be put in place to avoid and limit impacts.

The focus for any habitat restoration should be around the Umhlangane Tributary and the Glen Anil Stream. Wetland on the northern site should be the prime area of avoidance and mitigation planning.

Should any clarity be required with regards to any of the procedures contained within this Wetland Delineation Report, please contact SiVEST.

Greg Mullins Pr.Sci.Nat. Senior Environmental Scientist Environmental Division SiVEST

SiVEST Environmental Division 4 Pencarrow Crescent, La Lucia Ridge Office Estate, Umhlanga Rocks. 4320 PO Box 1899, Umhlanga Rocks. 4320 South Africa Tel +27 31 581 1500 Fax +27 31 566 2371 Email [email protected] www.sivest.co.za Contact Person: G.Mullins

Documents

Appendix K11 - GCS€¦ · 1.2 Site Description 1 2 WETLAND DELINEATION 3 2.1 Introduction 3 2.2 Legislation 4 2.3 Wetland Assessment 8 2.3.1 Methodology 8 2.3.2 Southern Site 8 2.3.2.1