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Transnet Collapsed Bridge wetland Assessment Report

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WETLAND DELINEATION AND ASSESSMENT FOR THE RECONSTRUCTION OF TRANSNET COLLAPSED BRIDGE AT

VANDERBIJLPARK, SERVICE ROAD

28 January 2016


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APPROVED BY:

……………………………………

Nonkanyiso Zungu, Pr.Nat.Sci (MSc, Env. Mngt)

Wetland Specialist

Date: 28 January 2016

Indemnity

This report is based on survey and assessment techniques which are limited by time and budgetary constraints relevant to the type and level of investigation undertaken. The findings, results, observations, conclusions and recommendations given in this report are based on the author‟s best scientific and professional knowledge as well as information available at the time of study. Therefore the author reserves the right to modify aspects of the report, including the recommendations, if and when new information may become available from ongoing research or further work in this field, or pertaining to this investigation. Although the author exercised due care and diligence in rendering services and preparing documents, she accepts no liability, and the client, by receiving this document, indemnifies the author against all actions, claims, demands, losses, liabilities, costs, damages and expenses arising from or in connection with services rendered, directly or indirectly by the author and by the use of this document.

TITLE: WETLAND DELINEATION AND ASSESSMENT FOR THE

RECONSTRUCTION OF TRANSNET COLLAPSED BRIDGE AT

VANDERBIJLPARK, SERVICE ROAD

COMPILED BY:

FIELD ASSISTANTS:

LUFUNO NEMAKHAVHANI

APHIWE-ZONA DOTWANA

STATUS OF REPORT:

DOCUMENT CONTROL

FINAL

IN000048/2015

FIRST ISSUE:

28 January 2016


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EXECUTUVE SUMMARY

1. INTRODUCTION

Transnet Capital Projects, a specialist unit of Transnet SOC Ltd, has appointed SAZI

Environmental Consulting to undertake wetland specialist studies for the collapsed bridge on the

Transnet Freight Rail service road in Vanderbijlpark along Houtheuwel-Potchefstroom railway line.

The field assessment was undertaken in December 2015.

2. Approach and Methodology

Various data sources were utilised to obtain background information, including 1:50 000

topographical Maps, NFEPA maps, and BCP map;

A site visit was undertaken to confirm the boundaries of the wetland on site;

Wet-Health tool was used for the assessment of the present ecological status or health of

the wetland;

Eco-Services tool was used for the assessment of ecological importance and sensitivity of

the wetland; and

Impact assessment was undertaken using the principles of the IWWMP operational

guidelines developed by the Department of Water and Sanitation.

3. Wetland Assessment Results

a. Catchment description

The study area falls within the C22H quaternary catchment of the Upper Vaal Water Management

Area (WMA, 8). Major rivers in the WMA are the Vaal and its tributary, the Wilge River. Other

tributaries to this WMA include the Klip, Liebenbergsvlei, Waterval, Suikderbosrand and Mooi

Rivers (DWAF, 2003). The assessed area transects the Rietspruit River catchment, a tributary to

the Klip River.

b. Classification of wetlands

A wetland is defined as a transitional area 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 (National Water Act; Act No. 36 of 1998). A Channelled Valley Bottom (CVB)


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wetland was identified on site, with an approximate width of 1Ha. A CVB wetland is a wetland with

a river channel running through it. The CVB identified on site was associated with Rietspruit River

of the Upper Vaal Water Management Area.

4. WETLAND HEALTH ASSESSMENT

Wetland ecological status was assessed by considering impacts to wetland hydrology,

geomorphology and vegetation. A summary of the findings is outlined in this report.

Prominent land use features surrounding the delineated wetland and within the wetland, includes:

Railway line; Road network (N1 and unpaved road); culverts, collapsed bridge, Rietspruit

River; livestock grazing.

The overall health scores are outlined on the table below.

HGM Unit

Hydrology Impact Score

Geomorphology Impact Score

Vegetation Impact Score

Overall Impact score

Health Category

Rietspruit CVB wetland 3 0.1 1.6 2 C


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5. WETLAND ECOLOGICAL IMPORTANCE AND SENSITIVITY

The assessed wetland which is a Channeled Valley Bottom wetland consists of ecological function

such as biodiversity support due to the presence of the riparian habitat. The assessed area falls

under the important area and the ecological support areas of the SANBI BGIS conservation plan.

However, no rare or red data species were identified in this area during the site assessment.

6. ASSESSMENT OF IMPACT

The assessed area is a natural wetland with minimal current impacts. These impacts include; river

bank erosion, pollution, upstream sewage effluent, woody debris and foam, and the collapsed

bridge, which alters the river flow and further contributes to river bank erosion. The proposed

development will have a few impacts on the wetland during the construction phase. These impacts

will include wetland disturbances by human interference and temporary buildings (offices) that will

be on the “no wetland zone” of the wetland. The rerouting of the river will impact on erosion and

loss or disturbance of the ecosystem.

7. CONCLUSION

The assessed area had minimal impacts and was moderately modified. The proposed activities will

also have low impacts during operational phase associated with alien invasion; and with proper

mitigation methods in place, impacts will be kept to a minimum. Based on the PES and EIS

assessments taken for the wetland study the current study approves the reconstruction of the

Transnet Collapsed Bridge.


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TABLE OF CONTENTS

EXECUTUVE SUMMARY ............................................................................................................... 3

TABLE OF CONTENTS .................................................................................................................. 6

LIST OF TERMS AND ABBREVIATIONS ....................................................................................... 8

1 INTRODUCTION ..................................................................................................................... 9

TERMS OF REFERENCE .............................................................................................. 11 1.1

DEFINITIONS AND LEGAL FRAMEWORK .................................................................... 11 1.2

2 APPROACH AND METHODOLOGY FOLLOWED ................................................................ 11

CONSULTED DATA SOURCES ..................................................................................... 11 2.1

DATA COLLECTION ...................................................................................................... 12 2.2

WETLAND DELINEATIONS ........................................................................................... 12 2.3

CLASSIFICATION OF WETLANDS ................................................................................ 13 2.4

EXISTING IMPACTS AND CATCHMENT CONTEXT ..................................................... 13 2.5

WETLAND HEALTH ASSESSMENT .............................................................................. 13 2.6

WETLAND ECOLOGICAL IMPORTANCE AND SENSITIVITY (EIS) .............................. 15 2.7

IMPACT ASSESSMENT ................................................................................................. 15 2.8

3 WETLAND ASSESSMENT RESULTS .................................................................................. 16

SITE DESCRIPTION ...................................................................................................... 16 3.1

CLASSIFICATION OF WETLANDS ................................................................................ 18 3.2

NATIONAL WETLAND INVENTORY (NWI) AND NFEPA .............................................. 21 3.3

4 WETLAND HEALTH ASSESSMENT .................................................................................... 23

HYDROLOGY ................................................................................................................. 23 4.1

GEOMORPHOLOGY ...................................................................................................... 24 4.2

VEGETATION................................................................................................................. 25 4.3

SUMMARY OF THE IMPACT SCORES ......................................................................... 26 4.4

5 WETLAND ECOLOGICAL IMPORTANCE AND SENSITIVITY (EIS) .................................... 27

6 ASSESSMENT OF IMPACT ................................................................................................. 28

Construction phase impacts ............................................................................................ 32 6.1

6.1.1 Loss and disturbance of wetland habitat .................................................................. 32

6.1.2 Alien Invasion of native species habitat .............................................................. 33

6.1.3 Water quality deterioration within wetlands ........................................................ 33


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Operational impacts ........................................................................................................ 33 6.2

6.2.1 Alien Invasion of native species habitat .............................................................. 34

6.2.1 Loss of natural habitat and ecological structure ................................................. 34

7 CONCLUSION ...................................................................................................................... 37

8 REFERENCES ...................................................................................................................... 38

LIST OF FIGURES

Figure 1: Layout map for the proposed collapsed bridge reconstruction study area ...................... 10

Figure 2: Wetland Hydro-Geomorphic setting ............................................................................... 13

Figure 3: The catchment and water resources adjacent to the study area ..................................... 17

Figure 4: Arial view of the assessed wetland associated with the Rietspruit River ......................... 18

Figure 5: Channelled valley bottom wetland within the study area ................................................ 20

Figure 6: NFEPA wetlands on site ................................................................................................ 22

LIST OF TABLES

Table 1: Health categories used by WET-Health for describing the integrity of wetlands ............... 14

Table 2: Ecological Importance and Sensitivity rating table ........................................................... 15

Table 3: Ranking scales for impact assessment ........................................................................... 16

Table 4: Description of the channelled valley bottom wetland ....................................................... 19

Table 5: Assessment of hydrological changes of the wetlands on the site .................................... 23

Table 6: Summary of impact scores and health category associated with changes in hydrology ... 24

Table 7: Assessment of geomorphological changes of the wetlands on the site ........................... 24

Table 8: Summary of the impact scores associated with geomorphological changes .................... 24

Table 9: Assessment of vegetation changes of the wetlands on the site ....................................... 25

Table 10: Summary of the Health scores associated with vegetation changes .............................. 25

Table 11: Summary of the wetland PES assessment .................................................................... 26

Table 12: Summary of the Overall Health scores .......................................................................... 26

Table 13: Generic hydrological functions performed by wetlands .................................................. 28

Table 14: current impacts observed on site ................................................................................... 29

Table 15: Summary of impacts associated with the proposed development .................................. 35


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LIST OF TERMS AND ABBREVIATIONS

BCP- Biodiversity Conservation Plan

Delineation – the technique of establishing the boundary of an aquatic resource such as a wetland or

riparian area.

Drain – In the context of wetlands, refers to a natural or artificial feature such as a ditch or trench created for

the purpose of removing surface and sub-surface water from an area (commonly used in agriculture).

Ecological Importance – An expression of the importance of an environmental resource for the

maintenance of biological diversity and ecological functioning on local and wider scales.

Ecological Sensitivity – A system‟s ability to resist disturbance and its capability to recover from

disturbance once it has occurred.

Eco-Services- A Technique for Rapidly Assessing Ecosystem Services Supplied by Wetlands

EIS – Ecological Importance & Sensitivity.

GIS – Geographical Information Systems.

GPS – Global Positioning System.

Gulley (or erosion gulley) - A gully (commonly called a “donga”) is an erosion landform or feature, created

by running water eroding sharply into soil. Gullies generally resemble small ditches that can be several

meters in depth and width. Gullying or gully erosion is the process by which gullies are formed.

HGM – Hydro-Geomorphic.

IWWMP- Integrated Water and Waste Management Plan

MBCP – Mpumalanga Biodiversity Conservation Plan

NFEPA – National Freshwater Ecosystem Priority Areas, identified to meet national freshwater conservation

targets (CSIR, 2010).

PES – Present Ecological State, referring to the current state or condition of an environmental resource in

terms of its characteristics and reflecting change from its reference condition.

SANBI – South African National Biodiversity Institute

Wet-health- A Technique for Rapidly Assessing the health of a wetland


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1 INTRODUCTION

Transnet Capital Projects, a specialist unit of Transnet SOC Ltd, has appointed SAZI

Environmental Consulting to undertake wetland specialist studies for the collapsed bridge on the

Transnet Freight Rail service road in Vanderbijlpark along the Houtheuwel-Potchefstroom railway

line. The field assessment was undertaken in December 2015. The project entails the following

activities;

Demolition of existing bridge; and

Design and reconstruction of the collapsed bridge,

The site is located at 26.598674 S; 27.783168 E coordinates, and is within Transnet property.


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Figure 1: Layout map for the proposed collapsed bridge reconstruction study area


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TERMS OF REFERENCE 1.1

SAZI Environmental Consulting cc (SAZI), an independent company was requested to undertake

an assessment of wetlands. The activities for this assessment include the following:

Desktop assessment of the site;

A site visit to confirm the presence or absence of wetland areas along the collapsed bridge;

Assessment of the catchment;

Assessment of the Present Ecological Status of wetlands on site (Level 1, Wet-Health);

Assessment of Ecological Importance and Sensitivity of wetlands on site (Level 2, Eco-

Services); and

Impact assessment of the proposed activities on the wetlands.

DEFINITIONS AND LEGAL FRAMEWORK 1.2

In a South African legal context, the term watercourse is often used rather than the terms wetland,

or river. The National Water Act, 1998 (Act No. 36 of 1998) (NWA) includes wetlands and rivers

into the definition of the term watercourse (DWAF, 2005).

The NWA, defines a riparian habitat as follows: “Riparian habitat includes the physical structure

and associated vegetation of the areas associated with a watercourse, which are commonly

characterised by alluvial soils, and which are inundated or flooded to an extent and with a

frequency sufficient to support vegetation of species with a composition and physical structure

distinct from those of adjacent land areas”.

The NWA defines a wetland as “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”.

2 APPROACH AND METHODOLOGY FOLLOWED

CONSULTED DATA SOURCES 2.1

The following data sources were used to inform the assessment:


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1:50,000 imagery as well as latest Google Map Imagery for desktop assessment of the site;

NFEPA wetland coverage, which shows location of FEPA wetland sites;

C-Plan 3 to get information on areas highlighted for terrestrial biodiversity conservation in

the Gauteng Province;

Wet-Health tool for the assessment of the present ecological status or health of the

wetland; and

Eco-Services tool for the assessment of ecological importance and sensitivity of the

wetland.

DATA COLLECTION 2.2

The topographical data was obtained from the Surveyor General‟s 1:50 000 toposheet data for the

region, namely 2627DB. Contours were combined from the topographical map sheets to form a

combined contours layer.

WETLAND DELINEATIONS 2.3

The riparian zone and wetlands were delineated according to the Department of Water Affairs

(DWA, previously known as the Department of Water Affairs and Forestry -DWAF) guideline, 2007:

A practical guideline procedure for the identification and delineation of wetlands and riparian

zones.

The guidelines indicate that wetlands must have one or more of the following attributes:

Wetland (hydromorphic) soils that display characteristics resulting from prolonged

saturation;

The presence, at least occasionally, of water loving plants (hydrophytes); and

A high water table that results in saturation at or near the surface, leading to anaerobic

conditions developing in the top 50 centimetres of the soil.

During the site investigation the following indicators of potential wetlands were identified:

Terrain unit indicator;

Soil form indicator;

River channel indicator;

Soil wetness indicator; and


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Vegetation indicator.

CLASSIFICATION OF WETLANDS 2.4

The session below includes breaking the wetland units into Hydro-Geomorphic types (HGM);

which are defined based on geomorphic setting (e.g. hillslope or valley bottom), water source

(surface water dominated or sub-surface water dominated) and how water flows through the

wetland unit (diffusely or channelled). Each wetland unit distinguished based on Hydro-

Geomorphic type, were assessed individually. Figure 2 below indicates the wetland Hydro-

Geomorphic setting of inland wetlands in South Africa as well as wetland classification applied on

wetlands for assessment.

Figure 2: Wetland Hydro-Geomorphic setting

EXISTING IMPACTS AND CATCHMENT CONTEXT 2.5

Using available information, existing impacts to the wetlands and within the delineated micro-

catchment were mapped and described.

WETLAND HEALTH ASSESSMENT 2.6

A level 2 Wet-Health method was used to determine the health of the wetland on site, thus

describing their Present Ecological status (PES) (Macfarlane, et al. 2008). This method utilises

geomorphology, hydrology and vegetation to determine the health of a wetland. The hydrology

module assesses the landuse descriptors (irrigation, level of reduction or increase in flows, Hydro-

Geomorphic setting of the wetland and extent of canalisation and gully formations). The vegetation

module assesses the level of vegetation transformation, which is indicated by level of alien species


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invasion, terrestrial species encroachment and encroachment by indigenous invasive species.

The geomorphology module captures deviations in the sedimentary inputs and outputs to and from

wetlands that are consequence of human activities.

Values range from Class A (largely natural) to Class F (critically modified). Table 1 describes the

overall HGM health categories and their scores. This is calculated as 10 -impact scores to get the

overall impact score.

Table 1: Health categories used by WET-Health for describing the integrity of wetlands

HEALTH

CATEGORY DESCRIPTION Min Score

A Unmodified, natural. 0 – 0.9

B

Largely natural with few modifications. A slight change in ecosystem

processes is discernable and a small loss of natural habitats and

biota may have taken place.

1 – 1.9

C

Moderately modified. A moderate change in ecosystem processes

and loss of natural habitats has taken place but the natural habitat

remains predominantly intact.

2 – 3.9

D Largely modified. A large change in ecosystem processes and loss

of natural habitat and biota and has occurred.

4 – 5.9

E

The change in ecosystem processes and loss of natural habitat and

biota is great but some remaining natural habitat features are still

recognizable.

6 – 7.9

F

Modifications have reached a critical level and the ecosystem

processes have been modified completely with an almost complete

loss of natural habitat and biota.

8 – 10

An overall wetland health score was calculated by weighting the scores obtained for each module

and combining them to give an overall combined score using the following formula:

Overall health rating = [(Hydrology*3) + (Geomorphology*2) + (Vegetation*2)] / 7.

This overall score assists in providing an indication of wetland health/condition which can in turn be

used for recommending appropriate management measures.


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WETLAND ECOLOGICAL IMPORTANCE AND SENSITIVITY (EIS) 2.7

An assessment of the importance and sensitivity of wetland systems using the Wetland EIS

(Ecological Importance and Sensitivity) assessment tool was undertaken using the outcomes of

the WET-Health assessment and other valuable information gathered in the field as well as

available desktop information. The tool includes an assessment of three components:

Biodiversity support;

Landscape scale importance; and

Sensitivity of the wetland to floods and water quality changes.

The maximum score for these components was taken as the importance rating for the wetland

which is rated using Table 2, below.

Table 2: Ecological Importance and Sensitivity rating table

RATING EXPLANATION

None, Rating = 0 Rarely sensitive to changes in water quality/hydrological regime.

Low, Rating =1 One or a few elements sensitive to changes in water

quality/hydrological regime.

Moderate, Rating

=2

Some elements sensitive to changes in water quality/hydrological

regime.

High, Rating =3 Many elements sensitive to changes in water quality/ hydrological

regime.

Very high, Rating

=4

Very many elements sensitive to changes in water quality/ hydrological

regime.

IMPACT ASSESSMENT 2.8

The information gained from the functional integrity and EIS assessments was used to inform an

assessment of the likelihood and significance of potential impacts associated with the proposed

mining activities. The following methodology (Table 3) has been adopted from the DWA‟s

Operational Guideline, 2010 entitled “Operational Guideline: Integrated Water and Waste

Management Plan”.


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Table 3: Ranking scales for impact assessment

DURATION (D) MAGNITUDE (M)

5 - Permanent 4 - Long term (ceases with operational life) 3 - Medium term (5-15 years) 2 - Short term (0-5 years) 1 - Immediate

10 - Very high/do not know 8 - High 6 - Moderate 4 - Low 2 - Minor

SCALE (S) PROBABILITY (P)

5 - International 4 - National 3 - Regional 2 - Local 1 - Site 0 - None

5 - Definite/do not know 4 - Highly probable 3 - Medium probability 2 - low probability 1- Improbable 0 - None

SIGNIFICANCE POINTS (SP) = (D+M+S) X P

HIGH (H) = >60 POINTS

MODERATE (M) = 30-60 POINTS

LOW (L) = <30 POINTS

NO SIGNIFICANCE = 0

POSITIVE IMPACT

The maximum value of significance points is 100. Environmental effects could therefore be rated

as either high (H), moderate (M), or low (L) significance, as seen above. The impact score for the

current assessment will be calculated in section 7.

3 WETLAND ASSESSMENT RESULTS

SITE DESCRIPTION 3.1

The collapsed bridge is located within the Transnet Freight rail line in Vanderbijlpark along the

Houtheuwel-Potchefstroom railway line, and forms part of the Transnet service road. The site is

located in Rietspruit 535 IQ farm. The site falls under the Jurisdiction of the Emfuleni Local

municipality in Vanderbijlpark, Gauteng Province.

The area falls under the C22H quaternary catchment and forms part of the Upper Vaal Water

Management Area refer to figure 3. The collapsed bridge crosses the Rietspruit River which is a

tributary to the Klip River. The assessed area is approximately 1ha in size. The surrounding area is

dominated by agricultural holdings and service roads.


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Figure 3: The catchment and water resources adjacent to the study area


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CLASSIFICATION OF WETLANDS 3.2

A wetland is defined as a transitional area 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 (National Water Act; Act No. 36 of 1998). A Channelled Valley Bottom (CVB)

wetland was identified on site, with an approximate width of 1ha located at 26.598674 S;

27.783168 E coordinates. A CVB wetland is a wetland with a river channel running through it. The

CVB identified on site was associated with Rietspruit River of the Upper Vaal Water Management

Area. Figure 4 depicts an overall picture of the assessed wetland with an Arial view of the

collapsed bridge.

Figure 4: Arial view of the assessed wetland associated with the Rietspruit River

Table 4 gives a description of the wetland type identified on site. Figure 5 thereafter indicates the

delineated wetland on site.


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Table 4: Description of the channelled valley bottom wetland

WETLAND TYPE DESCRIPTION

Channelled Valley

Bottom

Linear fluvial, net depositional valley bottom surfaces which have a

straight channel with flow on a permanent or seasonal basis. Episodic

low is thought to be unlikely in this wetland setting. The straight

channel tends to flow parallel with the direction of the valley (i.e. there

is no meandering), and no ox-bows or cut-off meanders are present in

these wetland systems. The valley floor is, however, a depositional

environment such that the channel flows through fluvially-deposited

sediment. These systems tend to be found in the upper catchment

areas.


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Figure 5: Channelled valley bottom wetland within the study area


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NATIONAL WETLAND INVENTORY (NWI) AND NFEPA 3.3

The Atlas of Freshwater Ecosystem Priority Areas in South Africa (Nel et al, 2011) which

represents the culmination of the National Freshwater Ecosystem Priority Areas project, a

partnership between SANBI, CSIR, WRC, DEA, DWA, WWF, SAIAB and SANParks, provides a

series of maps detailing strategic spatial priorities for conserving South Africa‟s freshwater

ecosystems and supporting sustainable use of water resources. Freshwater Ecosystem Priority

Areas (FEPA‟s) were identified through a systematic biodiversity planning approach that

incorporated a range of biodiversity aspects such as ecoregion, current condition of habitat,

presence of threatened vegetation, fish, frogs and birds, and importance in terms of maintaining

downstream habitat. High water yield areas and high groundwater recharge areas were also

identified as part of the project.

Based on the recently published Atlas of Freshwater Ecosystem Priority Areas in South Africa (Nel

et. al., 2011), the proposed project is within a channelled valley bottom wetland area, as seen in

figure 6.


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Figure 6: NFEPA wetlands on site


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4 WETLAND HEALTH ASSESSMENT

Wetland ecological status was assessed by considering impacts to wetland hydrology,

geomorphology and vegetation. A summary of the findings is outlined in this report.

Prominent land use features surrounding the delineated wetlands, and within the wetlands,

includes:

Road network;

Railway network;

Livestock grazing;

Rietspruit River;

Agricultural holding;

Collapsed bridge;

Walkways; and

Alien invasive species.

HYDROLOGY 4.1

The channelled valley bottom wetland on site was associated with the Rietspruit River; and has a

natural hydrology. Major hydrological impacts observed on site include; the collapsed bridge which

alters the water flow, and artificial water inputs from storm water channels. Water quality is

generally poor and the water chemistry is similar throughout the wetland, this is caused by sewage

effluent from the sewage treatment plant located upstream the Rietspruit River in Evaton.

Table 5 summarises the assessment of the hydrological changes of the wetland on site, and table

6 gives a summary of impacts scores and health category associated with changes in hydrology.

Table 5: Assessment of hydrological changes of the wetlands on the site

HGM Unit Overall Impact Score Health Category

Channelled valley bottom 3 C


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Table 6: Summary of impact scores and health category associated with changes in hydrology

IMPACT CATEGORY

DESCRIPTION SCORE HYDROLOGICAL HEALTH CATEGORY

None No discernible modification or the modification is such that it has no impact on hydrological integrity.

0 – 0.9 A

Small Although identifiable, the impact of this modification on hydrological integrity is small.

1 – 1.9 B

Moderate The impact of this modification on hydrological integrity is clearly identifiable, but limited.

2 – 3.9 C

Large The modification has a clearly detrimental impact on hydrological integrity. Approximately 50% of hydrological integrity has been lost.

4 – 5.9 D

Serious The modification has a clearly adverse effect on hydrological integrity. Well in excess of 50% of the hydrological integrity has been lost.

6 – 7.9 E

Critical

The modification is so great that the ecosystem processes of this component of hydrological health are drastically altered. 80% or more of the hydrological integrity has been lost.

8 – 10 F

GEOMORPHOLOGY 4.2

Geomorphological impacts associated with the assessed area, include the river bank erosion

caused by the collapsed bridge and the meandering state of the river.

Table 7 summarises the assessment of geomorphological changes of the wetland on site; Table 8

explains the impact scores associated with the geomorphological changes.

Table 7: Assessment of geomorphological changes of the wetlands on the site


Channelled valley bottom 0.1

A

Table 8: Summary of the impact scores associated with geomorphological changes

Threat Category Description Score

GEOMORPHOLOGY HEALTH

CATEGORY

None No discernable threat or the threat is such that no impact on wetland geomorphic integrity could be expected.

0 – 0.9

A


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Small Although identifiable, the threat posed could only be expected to have a small impact on wetland integrity.

1 – 1.9 B

Moderate The threat posed could be expected to have an identifiable, but limited impact on wetland integrity.

2 – 3.9 C

Large The threat posed could be expected to reduce wetland integrity by approximately 50%.

4 – 5.9 D

Serious The threat posed could be expected to reduce wetland integrity in excess of 50%.

6 – 7.9 E

Critical The threat posed could be expected to destroy ecosystem processes.

8 – 10 F

VEGETATION 4.3

Vegetation plays an important role in wetlands. Vegetation cover in a wetland helps the wetland to

hold water for longer periods of time and reduce run-off. The assessed wetland consisted of

common vegetation throughout the assessed area and the dominant vegetation time observed on

site was; Thermeda Triandra (red grass); Heteropogon contortus (Spear grass); hyparrhenia hirta

(Thatching grass). Other vegetation observed on site included the Typha capensis which was

predominant within the permanent zone of the wetland. Major impacts on vegetation includes the

presence of alien invasion species; Arundo Donax (Giant reed); Phragmites australis (Common

reed); Eucalyptus camaldulensis (River red gum); salix babylonica (Weeping willow). Alien

invasion species mentioned above are commonly known its consumption of water leading to drying

of wetlands, which is a major impact to wetlands.

Table 9 summarises the assessment of changes in vegetation of the wetland on site; Table 10

explains the impact scores associated with the changes in vegetation.

Table 9: Assessment of vegetation changes of the wetlands on the site


Channelled valley bottom 1.6

B

Table 10: Summary of the Health scores associated with vegetation changes

DESCRIPTION Score HEALTH Category

Vegetation composition appears natural. 0 – 0.9 A


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A very minor change to vegetation composition is evident at the site.

1 – 1.9 B

Compositional changes are evident but the site still contains mostly species expected in the reference state. Vegetation composition has been clearly altered but still contains a large proportion of natural species expected in the reference state.

2 – 3.9 C

Vegetation composition has been largely altered and introduced, alien and/or ruderal species are abundant but most characteristic wetland species are usually still present.

4 – 5.9 D

Vegetation composition has been substantially altered but some characteristic species remain, although the vegetation consists mainly of introduced, alien and/or ruderal species.

6 – 7.9 E

Vegetation composition has been totally or almost totally altered, and if any characteristic species still remain, their extent is very low.

8 – 10 F

SUMMARY OF THE IMPACT SCORES 4.4

When the results of the three modules detailed above are combined, the PES results for the

wetlands are shown in Table 11. Table 12 explains the summary of the overall health impact score.

Table 11: Summary of the wetland PES assessment

HGM Unit

Hydrology Impact Score

Geomorphology Impact Score

Vegetation Impact Score

Overall Impact Score

Health Category

Rietspruit CVB wetland 3 0.1 1.6 2 C

Table 12: Summary of the Overall Health scores

DESCRIPTION Score HEALTH Category

Unmodified, natural. 0 – 0.9 A

Largely natural with few modifications. A slight change in

ecosystem processes is discernible and a small loss of natural

habitats and biota may have taken place.

1 – 1.9 B

Moderately modified. A moderate change in ecosystem

processes and loss of natural habitats has taken place but the

natural habitat remains predominantly intact

2 – 3.9 C


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Largely modified. A large change in ecosystem processes and

loss of natural habitat and biota and has occurred.

4 – 5.9 D

The change in ecosystem processes and loss of natural habitat

and biota is great but some remaining natural habitat features

are still recognizable.

6 – 7.9 E

Modifications have reached a critical level and the ecosystem

processes have been modified completely with an almost

complete loss of natural habitat and biota.

8 – 10 F

5 WETLAND ECOLOGICAL IMPORTANCE AND SENSITIVITY (EIS)

Ecological Importance and Sensitivity is a concept introduced in the reserve methodology to

evaluate a wetland in terms of:

Ecological importance;

Hydrological functions; and

Direct human benefits.

The ecological importance of the assessed channeled valley bottom wetland was assessed based

on terrestrial and aquatic biodiversity.

The assessed wetland which is a Channeled Valley Bottom wetland consists of some ecological

functions which include biodiversity support due to the presence of the riparian habitat. The

assessed area falls under the important area and the ecological support areas of the conservation

plan. However, no rare or red data species were identified in this area during the site assessment.

These wetland types are important for flood attenuation due to their vegetation cover which is of

hydrological importance. Also they are generally important for their slow release of water during

low rainfall periods, and this is important in areas where livestock grazing is a source of livelihood.

Direct human benefits associated with this wetland included the livestock farming.

The hydrological function of the Channelled Valley Bottom wetland type is described in Table 13

below. These wetland types are thought to have a high erosion control function and limited water

quality enhancement ability.


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Table 13: Generic hydrological functions performed by wetlands

WETLA

ND

HYDRO

-

GEOMO

RPHIC

TYPE

Source of

water

maintaining

the wetland1

HYDROLOGICAL FUNCTIONS POTENTIALLY PERFORMED BY

THE WETLAND

Flood

attenuation

Stream flow

augmentati

on Erosi

on

contro

l

Potential for water quality

enhancement

Surface

Sub-

surface

Sediment

trapping

Phosp

hate

removal

Nitrates

Toxicants

Earl

y

wet

sea

son

Late

wet

sea

son

Earl

y

wet

sea

son

Late

wet

sea

son

1. Valley

bottom -

channell

ed

* * + 0

0

0 ++ + + + +

6 ASSESSMENT OF IMPACT

The assessed area is a natural wetland with few current impacts. These impacts include; river

bank erosion, livestock grazing, stock piling of concrete drain pipes located directly on the wetland,

woody debris and, sewage effluent, and the collapsed bridge, which alters the river flow and further

contributes to river bank erosion (refer to table 14).

Water source: 0 Contribution usually small

* Important contribution

Rating:

0 Function unlikely to be performed to any significant extent

+ Function likely to be present at least to some degree


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Table 14: current impacts observed on site

Woody debris

Collapsed bridge


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Alien invasive encroachment

Riverbank erosion

Alien invasive species


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Soil erosion

Livestock grazing


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Stock piling

Construction phase impacts 6.1

The proposed development will have a few impacts on the wetland that will be experienced during

the construction phase of the bridge. These impacts and their mitigation measures are discussed

below;

6.1.1 Loss and disturbance of wetland habitat

Mitigation:

Avoid additional wetland loss by limiting construction activities to as small an area as

possible;

Mark wetland areas with „No-Go‟ signage;

Limit all activities within the demarcated areas;

Include environmental awareness aspects into the site induction program to ensure all

construction staff are aware of the location and importance of wetland habitats;

Establish emergency response measures and a clearly defined chain of communication to

rapidly deal with any unforeseen impacts to wetlands, e.g. spills;

Regular cleaning up of the wetland areas should be undertaken to remove litter;


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No stockpiling of material may take place within the wetland areas and temporary

construction camps and infrastructure should also be located outside the wetland footprint;

Existing roads must be used as far as possible for access during construction; and

Re-vegetate cleared soil after construction for the control of soil erosion and water capacity

6.1.2 Alien Invasion of native species habitat

Mitigation:

Eradication of invasive species and weeds during the construction phase;

Removal of alien invasive species and monitoring of the environment to keep invasive

species to a minimum should they occur;

Removal of alien invasive species to allow native vegetation to grow to its potential; and

All daily activities that could involve the generation of waste should be restricted to the

construction site and away from any watercourse.

6.1.3 Water quality deterioration within wetlands

Mitigation:

Store and handle potentially polluting substances and waste in designated, bunded

facilities;

Waste should be regularly removed from the construction site by suitably equipped and

qualified operators and disposed of in approved facilities;

Locate temporary waste and hazardous substance storage facilities a minimum of 32m

from any wetland edge; and

Keep sufficient quantities of spill clean-up materials on site.

Operational impacts 6.2

Impacts envisaged during the operational phase includes, livestock grazing, alien invasion and

sewage effluent, none of these impacts will result from the Transnet reconstructed bridge.

Mitigation measures of these impacts are summarised below;


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6.2.1 Alien Invasion of native species habitat

Mitigation

Removal of alien invasive species during maintenance of the railway to keep alien species

to a minimum

6.2.1 Loss of natural habitat and ecological structure

Mitigation

Maintenance vehicles should be restricted to the Transnet access road to reduce any

further natural habitat loss

Refer to table 15 for a summary of impacts Associated with the bridge reconstruction.


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Table 15: Summary of impacts associated with the proposed development

Aspect Impact

Positive/negative

impact Probability Duration Scale Magnitude Significance/Risk

Impact

Significance

Mitigation

Required

Land clearing

Habitat

destruction Negative 4 2 1 6 36

Moderate

Yes

Land clearing

Soil loss/soil

erosion Negative 2 2 1 6 18

Low

Yes

Stream rerouting

Loss of

ecosystem Negative 3 2 1 8 33

Moderate

Yes

Toxic chemicals

from

construction

vehicles (oil,

petrol, brake

fluid etc.)

Alteration of

water quality

and water

pollution Negative 3 2 1 4 21

Low

Yes

Domestic waste

disposal

(littering)

Alteration of

water quality

and water

pollution Negative 4 2 1 4 28

Low

Yes


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Human

dispersal of

alien

seeds/sapling by

construction

vehicles, shoes,

clothes.

Alien

invasion of

native

species

habitat Negative 4 5 2 6 52

Moderate

Yes


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7 CONCLUSION

The assessed area had minimal impacts and was moderately modified. The proposed activities will

also have low impacts during operational phase associated with alien invasion; and with proper

mitigation methods in place, impacts will be kept to a minimum. Based on the PES and EIS

assessments taken for the wetland study the current study approves the reconstruction of the

Transnet Collapsed Bridge.


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8 REFERENCES

Davies B. and Day J. 1998. VANISHING WATERS. University of Cape Town Press. Rondebosch,

Cape Town, South Africa.

Basson, M.S. and Rossouw, J.D. 2003. Upper Vaal Water Management Area; Overview of water

resources availability and utilisation. National Water Strategy; Department of Water Affairs and

Forestry.

Kotze, D.C., Marneweck, G.C., Batchelor, A.L., Lindley, D.S. and Collins, N.B. 2009. Wet-

Ecoservices: A TECHNIQUE FOR RAPIDLY ASSESSING ECOSYSTEM SERVICES SUPPLIED

BY WETLANDS.

Macfarlane, D.M., Kotze, D.C., Ellery, W.N., Walters, D., Koopman, V., Goodman, P. & Goge, C.

2009. WET-HEALTH: A TECHNIQUE FOR RAPIDLY ASSESSING WETLAND HEALTH,

VERSION 2.

Nel, J.L., Driver, A., Strydom, W.F., Maherry, A., Petersen, C., Hill, L., Roux, D.J., Nienaber, S.,

van Deventer, H. Swartz, E. and Smith-Adao, L.B. 2011. ATLAS OF FRESHWATER

ECOSYSTEM PRIORITY AREAS IN SOUTH AFRICA: MAPS TO SUPPORT SUSTAINABLE

DEVELOPMENT OF WATER RESOURCES. Water Research Commission, Gezina. WRC Report

No. TT 500/11

OLLIS, D.J., SNADDON, C.D., JOB, N.M. & MBONA, N. 2013. Classification System for Wetlands and

other Aquatic Ecosystems in South Africa. User Manual: Inland Systems. SANBI Biodiversity Series

22. South African National Biodiversity Institute, Pretoria.

Directorate Water Resource Classification. Department of Water Affairs, South Africa, July 2011.

CLASSIFICATION OF SIGNIFICANT WATER RESOURCES IN THE OLIFANTS WATER

MANAGEMENT AREA (WMA 4): Integrated Units of Analysis (IUA) Delineation Report. Report

No: RDM/WMA04/00/CON/CLA/0311


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m: 084 800 0187

e: [email protected]

a: B16 Lone Creek, Waterfall Park, Vorna Valley, Midrand, 1684

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