Department of Environmental and Geographical Science Disaster

Department of Environmental and Geographical Science

Disaster Risk Science

Honours Thesis

Rainfall, Flooding and Infrastructure Damage in the Breede River Winelands Municipality: A Focus on Cut-off Low Events 2003 - 2008

Richard Donaldson 2009

Supervisor: Ailsa Holloway

ABSTRACTION

The BRWM is extremely at risk of flood events caused by cut-off lows. These cut-off lows are predicted to increase in severity and frequency due to climate change and natural variation. The Breede River flows through this area and due to the mountainous topography many tributary rivers flow from the mountains to the Breede River. The roads and bridges in the area are therefore increasingly vulnerable to flood events.

The environmental vulnerability caused by increased anthropogenic forcing (Aliens, water consumption, agriculture and urban development) and climate change contribute to the increasing vulnerability of infrastructure in the catchments of tributary rivers.

The management of the Breede River catchment has a large body of research to draw on and current strategies are competent and could solve many of the issues leading to environmental and infrastructural vulnerability. However, challenges develop in the implementation of these strategies and in the cooperation between departments in the municipality to mitigate the effects of flooding.

DECLARATION

I Richard Donaldson declare that this thesis s my own work and each contributor and quotation in this thesis has been cited and referenced. I understand that plagiarism is wrong and I I have not allowed, and will not allow, anyone to copy my work with the intention of passing it off as his or her own work

Signed

Date

TABLE OF CONTENTS

ABSTRACTION ...... I DECLARATION ...... II LIST OF FIGURES ...... V LIST OF TABLES ...... ERROR! BOOKMARK NOT DEFINED. ACRONYMS ...... VI DEFINITIONS ...... VI ACKNOWLEDGEMENTS ...... VII CHAPTER 1: INTRODUCTION ...... 1

1.1 BACKGROUND ...... 1 1.2 SEVERE WEATHER AND CLIMATE VARIABILITY IN THE BRWM ...... 3 1.3 AIMS AND OBJECTIVES ...... 3 1.4 LIMITATIONS ...... 4 1.5 ETHICAL CONSIDERATIONS ...... 5 1.6 ORGANISATION OF THESIS...... 5 CHAPTER 2: LITERATURE REVIEW AND CONCEPTUAL FRAMEWORK ...... 6

2.1 INTRODUCTION ...... 6 2.2 FLOODING AS A DISASTER RISK ...... 6 2.2.1 Flooding in a global context ...... 6 2.2.2 Flooding in South Africa focussing on the Western Cape ...... 8 2.3 FLOODING IN MOUNTAIN CATCHMENTS ...... 8 2.4 RISK DRIVERS FOR MOUNTAIN CATCHMENTS...... 9 2.4.1 Overview ...... 9 2.4.2 Agriculture and urbanisation in mountain catchments ...... 9 2.4.3 Infestation of alien vegetation in mountain catchments ...... 10 2.4.5 Impacts of wildfires on flooding in mountain catchments ...... 10 2.5 CLIMATE VARIABILITY AND CHANGE OF THE WESTERN CAPE ...... 11 2.6 PROPOSED CONCEPTUAL FRAMEWORK FOR THIS STUDY...... 12 CHAPTER 3 RESEARCH CONTEXT ...... 14

3.1 INTRODUCTION ...... 14 3.2 TOPOGRAPHY AND PHYSICAL CHARACTERISTICS...... 14 3.2.1 Topography ...... 15 3.2.2 Geology ...... 15 3.2.3 Lithology ...... 15 3.2.4 Vegetation ...... 16 3.2.5 Alien vegetation ...... 16 3.3 ENVIRONMENTAL AND INFRASTRUCTURAL VULNERABILITY IN THE BRWM ...... 17 3.3.1 Overview ...... 17 3.3.2 Current location of exposed critical infrastructure ...... 17 3.3.3 Current river conditions ...... 17 3.3.4 Disaster impacts and disruptions ...... 18 3.4 LOCAL CLIMATE AND WEATHER ...... 19 3.4.1 Current Conditions and future projections...... 19 3.5 HISTORICAL AND SOCIO-DEMOGRAPHIC PROFILE...... 20 3.5.1 History ...... 20 3.5.2 Demographic Profile ...... 20 3.6 ECONOMIC AND AGRICULTURAL PROFILE ...... 21 3.7 RECENT FLOOD AND SEVERE WEATHER HISTORY ...... 22

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3.7.1 Cut-off Low Pressure Systems ...... 22 3.7.2 Documented impacts ...... 23 CHAPTER 4: METHODOLOGY ...... 25

4.1 INTRODUCTION ...... 25 4.2 SECONDARY DATA COLLECTION ...... 25 4.2.1 Historic Rainfall Data and River Discharge Rates ...... 25 4.2.2 Wild Fires and Land use/ Land Cover ...... 26 4.2.3 Land use, Alien Infestation, Debris loading and Climate Change ...... 26 4.2.4 Recorded Economic Losses ...... 26 4.3 PRIMARY FIELD RESEARCH ...... 26 4.3.1 Semi Structured Interviews ...... 26 4.3.2 Direct Observations and Photographs ...... 27 4.3.3 Geo-Referencing Impacts and Vulnerabilities ...... 27 4.4 DATA CONSOLIDATION AND ANALYSIS ...... 27 4.4.1 Data Consolidation ...... 27 4.4.2 Data Analysis ...... 28 CHAPTER 5 FINDINGS ...... 30

5.1 INTRODUCTION ...... 30 5.2 RAINFALL AND PEAK RIVER DISCHARGE RATES TRENDS FOR SEVERE WEATHER 1980-2008 ...... 31 5.2.1 Rainfall trends 1980 – 2008 ...... 31 5.2.2 Peak Discharge Rate Trends in the Breede and Kogmanskloof Rivers 1980 – 2008 ...... 34 5.3 DESCRIPTION OF EXTREME WEATHER EVENTS 2003 – 2008 ...... 36 5.3.1 Rainfall ...... 36 5.3.2 Peak river discharge rates...... 38 5.4 RISK EXACERBATING FACTORS FOR RUN-OFF RISK...... 39 5.4.1 Land-use/ Land cover ...... 39 5.4.2 Wildfire occurrence ...... 40 5.5 ECONOMIC LOSSES 2003 – 2008 ...... 41 CHAPTER 6 ANALYSIS ...... 44

6.1 INTRODUCTION ...... 44 6.3 ANALYSIS OF PROXIMAL FLASH FLOOD HAZARD CONDITIONS FOR 2003, 2006, 2007,2008 ...... 46 6.4 ANALYSIS OF ADJUSTED ECONOMIC LOSSES ...... 47 6.5 SEVERE RAINFALL EFFECTS ANALYSIS IN RELATION TO CLIMATE CHANGE ...... 49 6.6 CURRENT MANAGEMENT STRATEGIES AND SOLUTIONS ...... 50 CHAPTER 7 DISCUSSION AND RECOMMENDATIONS ...... 51

7.1 INTRODUCTION ...... 51 7.2 MANAGERIAL RECOMMENDATIONS ...... 51 7.3 RESEARCH RECOMMENDATIONS ...... 52 REFERENCES ...... 54

MAPS AND GIS DATA ...... 57 APPENDIX A GENERAL GEOGRAPHIC CHARACTERISTICS ...... 58 APPENDIX B LAND USE/ LAND COVER AND WILDFIRES ...... 61 APPENDIX C EXPOSED INFRASTRUCTURE ...... 66 APPENDIX D FIELD PHOTOGRAPHS ...... 70

LIST OF FIGURES

FIGURE 1.1 THE SPATIAL EXTENT, MAIN TOWNS AND ROADS OF THE BRWM (WWW.AGIS.AGRIC.ZA/AGISWEB.AGIS.HTML) ...... 1

FIGURE 1. 2THE LOCATION OF THE BRWM WITHIN THE WESTERN CAPE PROVINCE AND SOUTH AFRICA (WWW.WIKIPEDIA.ORG) ...... 2

FIGURE 3. 1 GLOBAL DEATH TOLLS DUE TO FLOODING.WWW.EXTREMEWEATHERHEROES.ORG) ...... 7 FIGURE 3. 2 PROPOSED CONCEPTUAL FRAMEWORK ...... 13

FIGURE 5. 1 TRENDS FROM 1980-2008 IN THE AMOUNT OF RAINFALL, EVENTS AND DAYS OF RAINFALL PER YEAR (SAWS 2009) ...... 31 FIGURE 5. 2 THE NUMBER OF DAYS OF RAINFALL DURING EACH SEVERE WEATHER EVENT FROM 1980-2008 (SAWS 2009) ...... 32 FIGURE 5. 3 THE TOTAL AMOUNT OF RAINFALL THAT FELL DURING EACH SEVERE WEATHER EVENT FROM 1980-2008 (SAWS 2009) ...... 32 FIGURE 5. 4 THE FREQUENCY OF SEVERE WEATHER EVENTS PER YEAR 1980-2008 (SAWS 2009) ...... 33 FIGURE 5. 5 SHIFTING DISTRIBUTION OF SEVERE RAINFALL EVENTS IN THE BRWM FROM 1980-2008 (SAWS 2009) ... 33 FIGURE 5. 6 PEAK RIVER DISCHARGE RATES FROM 1980-2008 (DWAF 2009) ...... 34 FIGURE 5. 7 PEAK RIVER DISCHARGE RATES FROM 1980-2008 (DWAF 2009) ...... 35 FIGURE 5. 8 COMPARATIVE RAINFALL FOR SEVERE WEATHER EVENTS IN 2003, 2006, 2007, 2008 (SAWS 2009) ...... 37 FIGURE 5. 9 COMPARATIVE PEAK RIVER DISCHARGE RATES IN THE BRWM FOR SEVERE WEATHER EVENTS IN 2003, 2006, 2007, 2008 FOR ALL HYDROLOGICAL STATIONS (DWAF 2009) ...... 39 FIGURE 5. 10 NUMBER OF FIRES AND HECTARES BURNED PER YEAR 1976-2002 (WCNCB 2009) ...... 40 FIGURE 5. 11 DEPARTMENTAL DREAKDOWN OF ECONOMIC LOSSES AND PERCENTAGE CHANGE FROM 2003-2008 (INCEDENT REPORTS 2007, 2008, DIMP 2003, 2007) ...... 41

LIST OF TABLES

TABLE 3. 1 HISTORY OF FLOODING IN THE BRWM (SAWS 2009) ...... 22 TABLE 3. 2 RAINFALL AND AFFECTED AREAS FOR SELECTED SEVERE WEATHER EVENTS (INCEDENT REPORTS 2007, 2008, DIMP 2003, 2007) ...... 24

TABLE 4. 1 DATE CONSOLIDATION AND ANALYSIS ...... 27

TABLE 5. 1 TOTAL BREAKDOWN OF ECONOMIC LOSSES AND PERCENTAGE CHANGE FROM 2003-2008 (INCEDENT REPORTS 2007, 2008, DIMP 2003, 2007) ...... 43 TABLE 5. 2 ALL MUNICIPAL LOSSES FOR THE BRWM AND PROVINCIAL ROADS (DIMP 2009) ...... 43

TABLE 6. 1 SUMMERY OF TREND AVERAGES AND PERCENTAGE CHANGE OVER TIME ...... 44 TABLE 6. 2 TOTAL RAINFALL PER SEVERE WEATHER EVENT IN MM (SAWS 2009) ...... 46 TABLE 6. 3 MUNICIPAL ADJUSTED LOSSES AND PROVINCIAL ROADS 2003-2008 ...... 47 TABLE 6. 4 ALL ADJUSTED LOSSES FOR FLOOD EVENTS 2003-2008 (INCEDENT REPORTS 2007, 2008, DIMP 2007, 2003) ...... 47 TABLE 6. 5 COMPARISON OF MAXIMUM RAINFALL AND ADJUSTED TOTAL MUNICIPAL AND PUBLIC INFRASTRUCTURE LOSSES ...... 48 TABLE 6. 6 CORRELATION BETWEEN MAXIMUM RAINFALL AND ECONOMIC LOSSES...... 49

ACRONYMS

SAWS South African Weather Services DWAF Department of Water Affairs and Forestry AGIS Agricultural Geo-referencing Information System DiMP Disaster Mitigation for Sustainable Livelihoods Programme DEAT Department of Environmental Affairs and Tourism BOCMA Breede Overberg Catchment Management Agency NWRS National Water Resources Strategy WCNBC Western Cape Nature Conservation Board

DEFINITIONS

Cut-off low: Unstable and intense cold front that has become displaced equatorially out of the normal westerly current (Tyson and Preston- Whyte 2000). Climate Change: The change in the climate over a period of time that can be attributed to anthropogenic activity and natural variability (Midgley 2005). Debris Loading: The build up of debris in a river against a structure. Vulnerability: Conditions that can cause and increase in the susceptibility of an environment, structure or person to the impacts of a disaster.

ACKNOWLEDGEMENTS

I would like to thank all those who helped me with research. I would especially like to thank Dr Ailsa Holloway for always making time to help me, giving me guidance and assistance throughout my research.

I would like to thank the Cape Winelands Disaster Management, Breede River Winelands Disaster Management, the Breede River Winelands Traffic department, SAWS and DiMP for providing me with information and data to assist my research.

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CHAPTER 1: INTRODUCTION

1.1 Background

The Breede River Winelands Municipality (BRWM) lies in the middle catchment of the Breede River and is an important economic region of the Western Cape. The majority of its economic value lies in the agricultural sector, namely viticulture and fruit farming (BRWM IDP 2009). The sustainability and growth of this sector relies on an appropriate public infrastructure to service it. However, the greatest threat to this infrastructure comes from riverine flooding associated with severe weather events (DiMP 2007).

Figure 1.1 The spatial extent, main towns and roads of the BRWM (www.agis.agric.za/agisweb.agis.html)

Figure 1. 1The location of the BRWM within the Western Cape Province and South Africa (www.wikipedia.org)

Since 2003 there have been four severe weather events which have triggered significant damage to infrastructure in the BRWM. These extreme weather events cause an increasingly larger amount of damage with each event and therefore increase the cost of recovery due to construction inflation (DiMP 2007).

Severe weather events in the Western Cape come in the form of cut-off low pressure systems, which have increased in frequency and severity in recent years (Midgley 2005). The increase in frequency and severity of severe weather events will cause an increase in the cost of recovery, have a harmful effect on the economic output of the BRWM and increase the economic vulnerability of the population (DiMP 2007).

The overall economic loss caused by flooding has increase substantially from 2003 to 2008 and a large portion of this loss is attributed to road and bridge failure (DiMP 2007). The overall cost of flood events in the Western Cape has increased for R200 Million in 2003 to nearly R1Billion in 2008 (DiMP 2003, 2007, Incident Reports 2007, 2008).

1.2 Severe Weather and Climate Variability in the BRWM

The experience of repeat flood events in the BRWM illustrates the municipality’s exposure to severe weather and underlines the need to better understand the relationship between climate variability and sustainable development in municipalities such as the BRWM.

Climate variability and change has been identified as one of the most important influencing factors on severe weather events. The Western Cape is predicted to have a decrease in annual rainfall but an increase in the severity and frequency of severe weather events. There is also likely to be an increase in the average temperature which will have an effect on the soil moisture and moisture availability. The change in the climatic conditions will have a considerable effect on land use, land cover, alien vegetation infestation and wild fires, although there is currently no certainty as to what the effects will be (Midgley 2005).

1.3 Aims and Objectives

This project aims to investigate rainfall, riverine flooding and associated economic losses in the BRWM, with a specific focus on cut-off low events from 2003-2008.

To determine the aims of this thesis, the following objectives were met:

Examining and identifying trends in severe rainfall events from 1980- 2008 Examining and documenting trends in peak river discharge rates associated with specific heavy rainfall events from 1980-2008 Exploring potential changes in vegetative run-off exacerbating land cover due to wildfires from 1976-2002 Reviewing cut-off low events from 2003-2008, with respect to rainfall, peak river discharge and associated infrastructure loss within the municipality.

1.4 Limitations

There were a number of limitations experienced during the research process. There was difficulty in acquiring accurate economic loss data for specific infrastructure that had been damaged or destroyed and therefore some gaps in the data appear. Adjusting economic data to the year 2000 inflation level was problematic in that the calculation used to adjust economic data was at a national level and therefore inaccurate for all aspects of the reconstruction process (eg. Local building material, labour, transport.).

The presentation of GIS data was limited and due to a lack of in-depth knowledge of sophisticated software and is therefore slightly inaccurate in some cases.

Data from DWAF were restricted in robustness and therefore establishing a correlation between peak river discharge rates, rainfall and economic losses was problematic. Many of the smaller rivers in the Breede river catchment do not have accurate hydrological stations to measure river discharge rates, however using the Breede and Kogmanskloof gives a general understanding of discharge rates during severe weather events for the entire catchment.

Due to the lack of weather stations in the area, rainfall was only recorded in the urban centres and not in the higher altitude regions where different amounts of rainfall would be expected. This has a great effect when analysis the characteristics of a severe weather event in a mountain catchment as rainfall in the upper catchment is often more dangerous that rainfall on low- lying areas, as the steep rivers in the upper catchment will cause an increase in river discharge velocity.

1.5 Ethical Considerations

Certain consideration had to be taken into account during this study. The names of officials spoken to and interviewed during the research were not named, only there job title or place of work will be presented. Sensitivity will be used when highlighting challenges that influence municipal management and when discussing disaster losses. Copies of this thesis will be sent to all stakeholders as well as those interviewed.

1.6 Organisation of Thesis

The thesis will be organised into six chapters Chapter 1: Introduction Chapter 2: Literature review and presentation of the conceptual framework used Chapter 3: Research context description Chapter 4: presents the primary and secondary data collection methods and consolidation of the data collected Chapter 5: Presents the economic and physical findings of the research Chapter 6: Presents a conclusion with recommendations

CHAPTER 2: LITERATURE REVIEW AND CONCEPTUAL FRAMEWORK

2.1 Introduction

This chapter provides an overview of the major areas of literature that informed this study, specifically: Flood hydrology in mountain catchment areas including different types of flooding. The local environmental factors that influence riverine flooding was also focussed on, including land-use/ land- cover in relation to flood risk and wildfire impacts. Severe weather meteorology and flooding as a significant disaster risk on a global and local scale. This chapter concludes with the proposal conceptual framework for the organisation of this study.

2.2 Flooding as a Disaster Risk

2.2.1 Flooding in a global context

Endangering floods constitute a significant global risk. Between 1970 and 1999, flooding was associated with 90% of all deaths attributed to natural disasters and the economic losses, number of people affected and livelihoods lost has increased significantly over time. The increase in losses has been attributed to possible changes in the climate, but in most cases, it is due to a states inability to cope with disasters and, uniformed planning and development (Thomalla et al 2006).

There is currently a movement in the academic research towards an integrated approach between disaster risk reduction and climate change adaptation. This approach hopes to reduce the mitigate the losses sustained in future disaster events, namely flooding, by implementing preventative measures based on climate change predictions. This will mean that people can adapt to climate change and increase their resilience to disasters (Thomalla et al 2006).

Figure 3. 1 Global death tolls due to flooding.www.extremeweatherheroes.org) Figure 2.1 indicates the number of deaths due to all natural disasters as well as for floods, cyclones and earthquakes. There is an increasing trend in death tolls for all natural disasters between 1800 and 2000.

Recent literature reflects a shift towards assessing the relationship between flood damage (realised risk) and vulnerability. There is often no political reaction to risk perception and vulnerability until the realised risk of a flood is analysed (Messner 2005). Wisner and Blaikie’s pressure and release model show this relationship as Risk = Hazard X Vulnerability. This model therefore attributes the cause of vulnerability to the social and geophysical aspects and the hazard to the climatic conditions. After a disaster occurs, the realised risk can then be discovered (Wisner 2004)

2.2.2 Flooding in South Africa focussing on the Western Cape

The Western Cape experiences regular flood events, some triggered by seasonal winter rainfall and others by severe weather events, such as cut-off lows. Flooding is common throughout the Western Cape and occurs yearly. Cut-off lows have become more common in the East of the province and have cost the province millions of rands in economic damage each year due the recent increasing numbers and severity of cut-off lows (Midgley 2005). Due to the variation in topography flooding in mountain catchments is often fast (flash floods) and very damaging. Once water has reached the middle and lower catchments of rivers, water moves at a slower rate but inundates a larger area. Therefore the worst affected areas are those that are situated in the upper catchment as smaller tributaries that may be dry for most of the year have a rapid discharge rate during flood event and therefore cause the most damage (Douglas 2007).

2.3 Flooding in Mountain Catchments

Flooding is influenced by many factors, including: weather, topography, location, different land-use/ land-cover, flow and runoff rates, and types of watercourses. These determine the specific type of flooding an area will be exposed to (Douglas 2007).

With particular attention to mountainous regions, riverine flooding can occur at either a slow rate due to snowmelt or a fast rate due to flash flooding (NDMC, SAWS). Riverine runoff from mountain catchments is often the most damaging due to the narrow channels and speed of water travelling down a steep gradient. When this water reaches an urban area, obstructions in the watercourse can also cause a surge in the water level and flood the urban area causing losses (Douglas 2007).

2.4 Risk Drivers for Mountain Catchments

2.4.1 Overview

Surface runoff occurs when rainfall exceeds the infiltration capacity of the topsoil layer. The capacity of the topsoil to infiltrate rainwater can be increased or decreased due to many external forces. For example, if less water is able to infiltrate the soil due to man made hard surfaces or the presence of water resistant soil due to a recent wildfire, then the surface runoff will increase causing an increase in flood water and possible losses (Douglas 2007).

2.4.2 Agriculture and urbanisation in mountain catchments

Agriculture and urban development can increase surface runoff by increasing hard surfaces. This is known as surface sealing which decreases the infiltration ability of soils. The inappropriate proximity of agriculture and urban structures to riverbanks in the floodway will have the effect of removing natural riparian vegetation which acts as a buffer to reduce the speed of flood water and increasing steep river banks causing increased runoff. Infrastructure, such as that which is constructed across river obstructing the natural watercourse, can cause a surge in water levels due to vegetative debris loading during a flood event (Douglas 2007).

Agriculture changes the natural vegetation profile of the catchment by increasing or decreasing the biomass of the area. This will create an imbalance in the natural hydrological cycle and increasing or decreasing surface runoff (Bellot 2001). In areas with hard surfaces, tilling of the land can reduce runoff, whilst in saturated soil areas afforestation can increase evapotranspiration and reduce the water table (Naef 2002). The intensity of tillage and deep plough can however cause a macropore effect, decreasing the infiltration of water and causing an increase in surface runoff (Bronstert 2002).

2.4.3 Infestation of alien vegetation in mountain catchments

Similarly, infestations of alien vegetation increase the potential severity of flooding in severe weather events. The infestation of riparian zones by wooded aliens in particular, causes a 50% reduction the richness of understorey natural vegetation. Riparian vegetation acts as a buffer zone and reduces surface runoff during a flood event. It also controls the flow of materials downstream. The removal of riparian vegetation zones and the increasing infestation of alien vegetation will therefore cause an increase in surface and riverine runoff during a flood event. There is also an increased sediment build up underneath alien vegetation and the removal of alien vegetation during a flood (DWAF 2004).

During a flood event alien vegetation is susceptible to removal by flood waters. A river acts as an important corridor for the spread of alien vegetation. Flooding causes gaps or patches to form in the landscape, which are highly susceptible to infestation by aliens and therefore assist in the further spread of alien vegetation into areas previously free of aliens (Foxcroft 2008).

2.4.5 Impacts of wildfires on flooding in mountain catchments

Anthropogenic influences and alien vegetation can in some cases increase the natural fire cycle. Fires followed closely by severe weather events can be responsible for an increase in debris loading and surface runoff. Fires in the upper catchment of rivers will cause the removal of the riparian vegetation zone and if severe enough, can cause soils to become water repellent, due to a change in the chemical make up of the soils. This can lead to a decreasing in the channel hydraulic roughness and increase fire hardened surface. These two factors can lead to an increase in overland flow. In addition, the burning of riparian vegetation leaves behind large amounts of wooded debris while the loosening of roots reduces soil cohesion leading to an increase in soil erosion, thus there is a significant increase in the availability of loose sediment and vegetation that can move downstream during a flood event at higher speeds, increasing the risk of debris loading and causing infrastructural vulnerability (Cannon 2000).

2.5 Climate variability and change of the western cape

Although the influences of climate change are still being debated, several changes are anticipated for the Western Cape. Rainfall is predicted to decreases, while temperature and evapouration is expected to increase, causing the soils to dry out, leading to increased erosion and runoff. With the decrease in water availability both commercial and subsistence farming is likely to decrease with a potential for the occurrence of extended droughts (Midgley 2005).

Given these changing scenarios, the spread of alien vegetation may increase. This however depends on many variables, such as water availability and CO2. An increase in the frequency of high pressure systems, could cause an increase in berg winds and therefore and increase in fire risk (Midgley 2005).

There is current atmospheric research towards other causal factors behind the current climate variability trends that could influence the atmospheric patterns over the Western Cape. These include the Southern, Antarctic and Stratospheric Quasi-Biannual Oscillations. The full effect of these oscillations on Southern African climate is still not completely known (Van Aalst 2006). Following the Mississippi floods of 1993, much of the blame was attributes to anthropogenically induced climate change. However, recent other studies have show that the increasing rainfall during the 20th century may also be attributed to natural variation (Changnon 2005).

Many severe weather events in the Western Cape have occurred since 2003. These have been mainly attributed to cut-off low-pressure systems. Atmospheric factors that may influence the frequency of cut-off lows include the relationship between cut-off lows and La Nina. The Semi Annual Oscillation may also influence the cut-off low frequency, however no relationship was found to exist between cut-off low frequency and El Nino (Singleton 2006)

2.6 Proposed Conceptual Framework for this Study

The proposed conceptual framework for this thesis has been adapted from the disaster risk-pover approach in the 2009 global assessment report on disaster risk reduction. The framework shows the link between the municipal hazard drivers, exacerbating hazard drivers, proximal flood hazard and the realized risk.

The conceptual framework proposes a hypothetical chain of causation beginning with municipal scale hazard drivers. These drivers include the under funding of the municipality, poor management of the river catchment and the possible impacts of climate change and variability. These factors lead to the exacerbating hazard drivers, which include an increase in alien vegetation, wildfires, steepening riverbanks, infringement of urban and agriculture onto flood plains and a decrease in riparian vegetation. When combining these exacerbating hazard drivers, the outcome is a general increase in hard surfaces and general river catchment ecological decline. A combination of the municipal scale and exacerbating hazard drivers cause the third order hazards of increased run-off velocity and debris loading. When the hazard of a cut-off low with severe rainfall is introduced, the risk becomes realised in terms of major economic losses and repeat losses.

Figure 3. 2 Proposed conceptual framework

CHAPTER 3 RESEARCH CONTEXT

3.1 Introduction

The specific research context for this study is informed by a combination of the diver’s landscape that characterises the BRWM. Along with the heavy dependence on agriculture and a significant exposure to severe weather that has been associated with major economic losses. These are described below.

3.2 Topography and Physical Characteristics

Figure 3.1 Topography and physical characteristics of the BRWM

3.2.1 Topography

The BRWM lies in the Cape Fold mountain range in the middle catchment of the Breede River. There are three main mountainous regions that divide the municipality namely, the Waboomberg to the north, the Langeberg in the centre and the Riviersonderendberg to the south. The towns of Robertson, Ashton, Montagu and Bonnievale are situated near the Langeberg and therefore all experience a similar climate, precipitation and vegetation. McGregor is situated in the south, near the Riviersonderendberg. It is situated in a rain shadow and therefore receives less precipitation then the other towns and higher temperatures, it is also located at a higher altitude and not in a river valley, therefore has less exposed vulnerability (www.deat.gov.za/Enviro- Info/prov/intro.htm).

3.2.2 Geology

The underlying geology of the area is very diverse due to the topography. The areas around Robertson and Ashton show fluvial deposits and enon formations, due to the large amounts of riverine runoff in from the Langeberg Mountains. Areas around Montagu, Bonnievale and McGregor contain Table Mountain group and Bokkeveld group geology (Ninham Shands 2003) (See appendix A).

3.2.3 Lithology

The lithology in the Robertson and Ashton area is composed of conglomerate and sandstone whilst the areas around Montagu, Bonnievale and McGregor also contain sandstone along with shale and siltstone (Ninham Shands 2003). This lithology could be attributed to the erosivity of the Langeberg mountain above Robertson and Ashton, whilst other areas have more gentle slopes and therefore experience less erosion (www.agis.agric.za/agisweb/agis.html) (See Appendix A).

3.2.4 Vegetation

Vegetation biomes in the BRWM are similar to that of the rest of the Western Cape due to its similar climate and rainfall patterns. The majority of the vegetation biomes in the area consist of Fynbos, Rynosterveld, grassland, shrublands and some areas of forests. Forested areas are concentrated in the high altitude regions and to a lesser degree in riparian zones. Veld types around the low lying Robertson, McGregor and Bonnievale areas consist of Karoo and Karriod. The Langeberg and Montagu areas consist of Sclerophyllous bush types and False Sclerophyllis bush types whilst the Ashton area and lower Kogmanskloof River consist of temperate and transitional forest and scrub types (Ninham Shands 2003) (See Appendix A)

3.2.5 Alien vegetation

The Western Cape is one of the most heavily invaded provinces by alien vegetation. The worst effected areas in the Western Cape lie in the mountainous and coastal areas. Approximately 47% of the Breede River catchment is invaded by aliens. The most heavily infested areas are riparian vegetation zones in the upper catchments of tributary rivers to the Breede River and along the banks of the Breede River (La Maitre 2000).

The middle Breede River catchment and Kogmanskloof catchment constitute the most infested sub catchments in the Breede River catchment. The most predominant species include Acacias, Eucalyptus, Prosopis and Hakea. These are larger wooded trees that consume more water then the natural riparian vegetation thereby reducing the natural runoff of rivers. The need for these aliens to consume large amounts of water causes them to naturally infest riverine areas, out competing the natural vegetation and spreading at a greater speed. Predictions for future reductions in runoff show a current 8% decreasing in runoff, increasing to 32% by 2040. The approximate cost of removing alien vegetation in the Middle Breede and Kogmanskloof catchment stood at R18.5 million (Ninham Shands 2003) (see appendix B).

3.3 Environmental and infrastructural vulnerability in the BRWM

3.3.1 Overview

Currently the towns and infrastructure of the municipality are situated in areas that are susceptible to yearly flooding. Due to the mountainous topography, most access routes in the municipality cross rivers and the towns of Robertson, Ashton and Montagu are located in close proximity to rivers. (IDP 2009)

3.3.2 Current location of exposed critical infrastructure

The current vulnerable infrastructure can be clearly seen in appendix C. These maps show the vulnerable roads and bridges that cross rivers in or near urban areas. Appendices E show the photographic images of vulnerable bridges and roads.

All rivers hold the potential to cause large scale infrastructural failure in the event of a flood. The rivers in the BRWM can vary in the extent of damage they cause due to there proximity to infrastructure and agriculture. The towns of Montagu, Aston and Robertson suffer the greatest economic losses during flood events and have the highest levels of exposed infrastructure. Therefore the status of catchments on the Keisies, Kingna, Kogmanskloof, Willemnels, Droe and Hoop rivers is an important factor in understanding the vulnerability of infrastructure situated on these rivers.

3.3.3 Current river conditions

The upper catchments of the Hoop, Droe and Willemnels rivers have high levels of alien infestation and fall into a fire risk area that has seen many fires in the recent past. Agriculture is practiced in the form of viticulture and fruit farming on the banks of the rivers high in the catchment. These rivers flow through the town of Robertson (Ninham Shands 2003, www.agis.agric.za/agisweb/agis.html).

The Keisies and Kingna rivers flow into the town of Montagu and combine into the Kogmanskloof River. The catchment of the Kingna and Keisies rivers lie to the West and East of Montagu and support viticulture and fruit farming. Many tributaries flow to these rivers from the Langeberg and Waboomberg mountains. Alien infestation levels appear higher in the Kingna catchment, with well preserved riparian zones in some places. The river valleys are narrow and therefore road infrastructure lies close to the rivers. The two rivers converge at the Voortrekker Bridge (Ninham Shands GIS 2003, www.agis.agric.za/agisweb/agis.html).

3.3.4 Disaster impacts and disruptions

During flood events Montagu is effectively cut into three parts Access South is cut at the Voortrekker Bridge and access North East and West is cut at the Badens Bridge and van der Merwe Bridge. The Kogmanskloof River flows through the only pass in the Langeberg mountains and the R62 road is therefore vital for the transport connection in the area. The Kogmanskloof pass road is very low lying on the floodplain of the river and infested with Alien. The River flows through Ashton on its way to the Breede River and cuts access to the East during flood events (Ninham Shands GIS 2003) During flood events Robertson is effectively cut in half and access to the west is cut at the R60 bridge, whilst access to the east is cut by the kogmanskloof river in Ashton. Roads linking these towns to Bonnievale and McGregor are also affected by debris, rockfalls and water which can make them inaccessible at times. (www.agis.agric.za/agisweb/agis.html).

3.4 Local Climate and Weather

3.4.1 Current Conditions and future projections

The BRWM experiences a Mediterranean climate with cool wet winters and warm dry summers. During the summer months, the average maximum temperature is 25ºC - 30ºC with an average rainfall of 0 – 10mm. During the winter months, the average maximum temperature is 15ºC - 20ºC with an average rainfall of 25mm – 40mm of rainfall. This gives and average annual rainfall of approximately 400mm. (www.saexplorer.co.za/southafrica/climate/robertson_climate.asp, www.agis.agric.za/agisweb/agis.html).

These averages vary across the municipality due to the varying topography, which causes an increase or decrease in temperature and rainfall caused by orthographic rainfall and rain shadows. Areas of higher altitude receive more precipitation due to orthographic rainfall and can receive between 400mm – 1600mm of rainfall per annum (Ninham Shands 2003) ( see appendix A).

Future predictions for the Western Cape show an increase in temperature and evapouration. This will lead to a drying of soils and hardening of surfaces causing an increase in runoff during rainfall. Rainfall could become augmented by the topography of the BRWM with predictions of an increase in rainfall at higher altitudes and a decrease of rainfall in lower plains. This could be caused from a weakening of the synoptic forcing whereby there is an increasing frequency of weak low pressure systems causing increased high altitude rainfall. A decrease in rainfall days is predicted causing an increase in the severity and frequency of extreme weather events (Midgley et al 2005).

3.5 Historical and Socio-Demographic Profile

3.5.1 History

The towns of Robertson, Montagu and McGregor were founded in the mid 19th century as service towns to the local agricultural population. Montagu was seen as a vital access point for transport into the interior and was therefore situated at the Northern entrance to the Kogmanskloof valley. The development of the towns of Bonnievale and Ashton came in the late 19th century as a product of railway stations. The area began cultivating vineyards and orchards when settlers arrived but became better known for the ostrich feather industry. After WWI, the ostrich industry collapsed and attention began to increasingly turn towards the cultivation of vineyards. In the 1940’s the town of Ashton began canning fruit causing an increase in orchard cultivation along the Keisie and Kingna rivers. Agriculture has remained the Municipalities largest source of revenue and employment (BRWM IDP 2009).

3.5.2 Demographic Profile

The Breede River Winelands Integrated Development Plan for 2009 (IDP) estimates that the current population is 80 100. The Coloured population group makes up the largest majority with approximately 70% followed by the White and Black groups at approximately 15% each. Afrikaans is the predominant language spoken in the area. The urban areas in the municipality are currently growing at a steady rate as people move into the towns from rural areas due to the current economic downturn of the agricultural industry. Reports also show a slow pattern of migration of people towards the economically growing areas of Southern Coastal regions. There is however a seasonal migration of labour to the rural areas at harvest times and an increase in seasonal holidaymakers to the growing number of Breede River holiday resort (BRWM IDP 2009). As of the 2001 consensus, the BRWM was reported to have an employment rate of 88%, with the majority of employment being attributed to the primary sector and approximately only 15% employed in skilled or semi skilled labour (www.statssa.gov.za).

3.6 Economic and Agricultural Profile

The BRWM makes a 12% contribution to the Western Capes GDP, with agriculture comprising 19% of the local GDP and employing 11% of the labour force on approximately 800 farms. In resent years the agricultural sector has been negatively affected by the volatility and strengthening of the Rand, increased international competition, increased production costs and the declining quality of agricultural research and development. 30% of the arable land in the BRWM is has been identified for land redistribution, however only 2.4 % of that land has so far been redistributed. (BRWM IDP 2009).

The majority of land-use in the area is attributed to agriculture. The majority of land in proximity to major rivers is used for viticulture, with some areas along the Kogmanskloof, Keisies and Kingna rivers being used for Orchards. Agricultural areas situated away from the main water sources are used for dry crops and grazing. The Major rivers in the area flow through valleys, the largest being the Breede River Valley, much of the region is mountainous and not suitable for agriculture. Dryland crops are found further from rivers and are more common north of the Langeberg. The intensity of agriculture diminishes further north as rainfall is less and the terrain is less conducive to agriculture and more suited to grazing (BRWM IDP 2009).

Agriculture in the BRWM has been growing at a historic rate of 14% per year but has decrease to just 0.7% due to spatial constraints (Ninham Shands 2003). In order to maximise profits and find space for the constant and historic growth there is a need to cultivate as much as possible, which includes cultivating as close to the river bank as possible and as high in the catchment as possible. This often involves bulldozing out into a river bed with a reduced river.

Future projections for land-use and cover remain uncertain, however climate change reports have predicted that there may be a decrease in viticulture due to decreasing rainfall (Carter 2006) and an increase in alien vegetation due to many variables (Midgley 2005).

3.7 Recent Flood and Severe Weather History

Flooding in the BRWM is not uncommon, however due to the large spatial extent of the area and mountainous topography, the damages caused by heavy rainfall can vary significantly. Since 1980 there have been 8 severe flood events that have recorded heavy economic losses (DiMP 2003, 2007). The most damaging flood events occur when large amounts of rain fall over a shorter duration. It is often difficult to determine the exact amount of rain that falls due to the topography of the area (Singleton 2006).

Decade Years with Years with Total floods with floods with number or large losses little losses flood events 1980-1989 1981 1982, 1989 3 1990-1999 1991, 1993, 1994, 1998 5 1996 2000-2008 2003, 2006, 2004, 2005 6 2007, 2008

Table 3. 1 History of flooding in the BRWM (SAWS 2009)

Since 2003, four severe weather events associated with cut off lows have been reported. These four events have been associated with infrastructural failures and large scale economic loss.

3.7.1 Cut-off Low Pressure Systems

A cut-off low pressure system is an unstable and intense cold front that has become displaced equatorially out of the normal westerly current. It continues to move Eastwards as slower rate then a normal cold front therefore releasing larger amounts of rain over a smaller area (Tyson and Preston-Whyte 2000).

Southern Africa experiences on average eleven cut-off lows per year, the area covered and severity of these cut-off lows vary greatly (Singleton 2006).

3.7.2 Documented impacts

The recent increase in the construction of holiday resorts and residences close to rivers in the area and the location of houses in the pre-existing towns are all exposed to flooding (BRWM IDP 2009). In 2008 many holiday homes in the Avalon Springs resort were washed away. Construction on river banks or within flood plains increases the risk of soil erosion and increased debris loading. The current management strategy of reinforcing river banks using gabions as retaining walls may be a risk driver (BRWM IDP 2009).

It is easy to attribute blame for the damages caused by a flood to poor engineering, however it is often the case that previous designs were no built to withstand the current scale of disaster events on a changing landscape (Changnon 2005).

Table 3.3 below reflects the scale of economic losses associated with cut-off lows from 2003 to 2008. The total losses for all areas affected stands at nearly R3 Bil, with the BRWM suffering R41 mil (DiMP 2003, 2007).

Date Heaviest Rainfall in Areas Affected BRWM Areas Affected Other Damage Recorded BRWM 23-26 March 2003 Montagu 180mm Montagu, Ashton, Eden and Overberg R 212 422 663

Robertson Districts 22-24 August 2006 Tot-u-Diens 65mm Robertson, Montagu Eden and Overberg R 510 469 497

Districts 20-22 November 2007 McGregor 65mm McGregor, Robertson Eden and Overberg R 1 181 436 762

Districts 10-13 November 2008 Tot-u-Diens 115mm Montagu, Ashton, Eden and Overberg R 949 251 792

Robertson Districts

Total Damages R 2 853 580 715

Table 3. 2 Rainfall and affected areas for selected severe weather events (Incedent reports 2007, 2008, DiMP 2003, 2007)

CHAPTER 4: METHODOLOGY

4.1 Introduction

This research was undertaken as a descriptive case study to identify the flash flood hazards and contributing risk factors that increase the likelihood of public infrastructure failure during cut-off low weather events in the BRWM. As such it required the collection and review of a diverse range of secondary data sources as well as primary data collection through field visits to the municipality.

4.2 Secondary Data Collection

A wide range of secondary data sources were drawn on for this study, these included: Historic rainfall data Recent data on river discharge rates associated with flood events Land use/ land cover change data for the area Data on the recent wild fires Economic loss data for failed or damaged public infrastructure due to flash flooding Additional data on alien infestation

4.2.1 Historic Rainfall Data and River Discharge Rates

Historic rainfall data from the years 1980 to 2008 sourced from the South African Weather services (SAWS), with data from the Robertson, Ashton and Montagu weather stations specifically informing trends for severe weather events. Data were collected from the Department of Water affairs and Forestry (DWAF) to determine river discharge rates during flood events and determine trends in peak discharge rates.

4.2.2 Wild Fires and Land use/ Land Cover

Fire history data for the area were collected from the Western Cape Nature Conservation Board (WCNCB) Scientific Services GIS. Similarly land use data were collected from the Agricultural Geo- Referenced Information System (AGIS) in the form of GIS data. GIS data were also collected from the Ninham Shands 2003 report on the Breede River.

4.2.3 Land use, Alien Infestation, Debris loading and Climate Change

The data on these subjects were collected through current print journals and relevant reports.

4.2.4 Recorded Economic Losses

Economic data on damaged or destroyed public infrastructure due to flash flooding were sources directly form the municipal engineer, the traffic department and DiMP.

4.3 Primary Field Research

Primary field research took place over 10 days from June to August. It comprised semi-structured interviews with selected informants, as well as field observations

4.3.1 Semi Structured Interviews . The BRWM disaster manager was interviewed along with the municipal engineer and head of the traffic department, to gain an understanding of the infrastructure vulnerability and a history of flood losses.

4.3.2 Direct Observations and Photographs

All areas of the towns and major roads exposed to flash flooding in the municipality were observed and 29 bridges were photographed. This was done to compare historic photographs taken after flood events, to determine repairs and current vulnerability. River bank observations, observed the current status of the rivers and their riparian vegetation, along with alien vegetation infections

4.3.3 Geo-Referencing Impacts and Vulnerabilities

All roads and bridges in close proximity to rivers are seen as being vulnerable to damage during a flood event and therefore geo-referencing of all vulnerable areas took place. Google Earth, current topographic maps and street maps were used to geo-reference vulnerable areas.

4.4 Data Consolidation and Analysis

4.4.1 Data Consolidation

The diversity of secondary data sets necessitated systematic consolidation over time and space, and in specific relation to documented flash flood events. This is summarised in table 4.1 below. Data set and Consolidation Rationale Source Method Historic Excel To determine rainfall general trends and Rainfall changing rainfall patterns during severe (SAWS) weather events River Excel To document peak discharge rates during discharge severe weather events and identify overall Rates trends (DWAF) Wild fires Excel To determine the general wildfire severity and (WCNCB) frequency trend Economic Excel To determine the losses sustained to public losses infrastructure from 2003 - 2008 Table 4. 1 Date consolidation and analysis

4.4.2 Data Analysis

Rainfall Daily data for Robertson, Ashton and Montagu for 1980 – 2008 were consolidated to determine the annual average rainfall, number of annual rainfall events and number of days of recorded rainfall. To determine the temporal distribution of severe weather events, the heaviest amount of rain per day from any of the three weather stations was calculated. While this generated a higher then average value, it emphasised the potential for heavy precipitation days for the purpose of generating trends over time. A rainfall event was defined as one or more consecutive days of rainfall where more then 1mm of rainfall fell per day, 1267 of these rainfall events were identified and then ranked according to the total amount of rainfall that fell over all days of the event. The upper quartile consisted of rainfall events were more then 90mm of rainfall had fallen. Therefore a severe weather event was defined as one or more consecutive days where the total rainfall was greater then 90mm and 55 were identified. These severe weather events were then graphed to determine trends in the number of days per event, the amount of rainfall per event, the yearly frequency and monthly distribution of events.

Daily rainfall data for specific severe weather events from 2003 – 2008 were collected and compared to each other and the thirty year trend.

Peak discharge rates In order to establish peak river discharge rates associated with severe weather events, the dates of the severe weather events established above were identified. Peak discharge rates for the Breede and kogmanskloof Rivers were then calculated against the identified severe weather events. These were then graphed to identify trends in peak river discharge rates to severe weather events from 1980 – 2008.

Peak river discharge rates were also identified for specific severe weather events from 2003 -2008. Data was collected from the Peitersfontain, Kogmanskloof, Keisers and Breede River East and West. The western station is located after the Kogmanskloof joins the Breede River. These were compared with rainfall data and with the peak river discharge trends from 1980.

Wildfires

Wildfire data from the Langeberg Mountains was collected from 1976 -2002. This data yearly frequency of fires was compared with the amount of hectares burned yearly and with each fire to determine if there was a trend.

Economics

Due to inflation, all costs were adjusted to be equivalent to losses sustained in 2000. The reason for this is to determine whether the damage caused by floods is merely increasing due to inflation or that the level of destruction is greater (Leiman). Economic data was broken up to determine the exact costs for infrastructure failure in the BRWM and compared from 2003 – 2008 to establish trends.

CHAPTER 5 FINDINGS

5.1 Introduction

The findings of this thesis are numerous, complex and often interconnect separate areas of study. They describe rainfall and river discharge rate trends from 1980-2008 including evidence of past severe weather events, and a comparison of the flood events from 2003 – 2008 including their economic losses, rainfall and hydrological difference. They also examine land use and cover in the municipality including risk drivers. Lastly, this chapter seeks to identify the vulnerable public infrastructure exposed to flash flood events as well as current management strategies.

The priority focus of the research was on the urban areas that are most affected by severe weather events. For this reason, data for determining rainfall trends, land use, land cover and fires focussed on the areas surrounding the towns Robertson, Ashton and Montagu. The towns of McGregor and Bonnievale suffer less from flood events due to their location and geography. All important tarred roads in the municipality were taken into account when assessing the vulnerability of public infrastructure and economic losses.

5.2 Rainfall and Peak River Discharge Rates Trends for Severe Weather 1980-2008

5.2.1 Rainfall trends 1980 – 2008

Annual Trends of Rainfall events, Days of Rainfall and Average Annual Rainfall R2 = 0.0033 R2 = 0.0022 R2 = 0.0374

140 140

120 130

100 Events 120 Days

Amount 80 Linear (Amount) 110 Linear (Events) 60 (mm) Rainfall Linear (Days)

100

90 20

0 80 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 Figure 5. 1 Trends from 1980-2008 in the amount of rainfall, events and days of rainfall per year (SAWS 2009)

Figure 5.1 shows the linear trend in rainfall patterns across the BRWM. These findings show a small and steady decrease in the number of days in which rainfall is recorded by 1.83% and the annual amount of rainfall recorded by 12.5%. The figure shows an increase in the amount of rainfall events recorded per year by 4.77%.

Days of Rainfall in + 90mm Rainfall Events

8 DaysRainfall of

1981 1981 1981 1981 1982 1982 1983 1983 1985 1987 1988 1989 1989 1990 1991 1992 1992 1992 1993 1993 1994 1994 1994 1994 1995 1995 1995 1996 1996 1997 1997 1997 1997 1998 1998 1998 2000 2000 2001 2002 2003 2004 2004 2005 2005 2006 2006 2006 2006 2007 2007 2007 2008 2008 1980 Figure 5. 2 The number of days of rainfall during each severe weather event from 1980-2008 (SAWS 2009)

Total Amount of Rainfall in + 90mm Rainfall Events

500

450

400

350

300

250

200 Amount of Rainfall

150

100

1981 1981 1981 1981 1982 1982 1983 1983 1985 1987 1988 1989 1989 1990 1991 1992 1992 1992 1993 1993 1994 1994 1994 1994 1995 1995 1995 1996 1996 1997 1997 1997 1997 1998 1998 1998 2000 2000 2001 2002 2003 2004 2004 2005 2005 2006 2006 2006 2006 2007 2007 2007 2008 2008 1980 Figure 5. 3 The total amount of rainfall that fell during each severe weather event from 1980-2008 (SAWS 2009)

Figures 5.2 and 5.3 Show the linear trends in severe weather events. The figures show an increase in the volume of rain recorded per event by 32% and a 21% decrease in the number of days over which the rainfall was recorded. This therefore indicates that during a severe weather event, more rainfall falls over fewer days.

Frequency of Severe Events

2 Number of Events of Number

1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008

Figure 5. 4 The frequency of severe weather events per year 1980-2008 (SAWS 2009)

Figure 5.4 shows the number of severe weather events recorded per year. The linear trend shows a marked increase in the frequency of severe weather events in the BRWM by 53%.

Monthly Distribution of Severe Events

4 1980-1989 1990-1999 2000-2008 3

0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Figure 5. 5 Shifting distribution of severe rainfall events in the BRWM from 1980-2008 (SAWS 2009)

Figure 5.5 shows a significant change in the distribution of severe weather events from 1980-2008. There is an apparent shift of severe weather events from the spring season in March and April to the mid winter season in July. This could account for the increasing economic cost due to the appearance of severe weather events at a time of year when the ground could already be saturated from winter rainfalls. The figure also shows an increase in the frequency of severe weather events later in the year, peaking in November.

5.2.2 Peak Discharge Rate Trends in the Breede and Kogmanskloof Rivers 1980 – 2008

Breeder River West Discharge Rate Peaks during Severe Weather Events

1200

1000

800

600 DischargeRates

400

200

6/04/1982 2/07/1985 4/07/1996 5/04/1997 8/05/1998 2/07/2001 6/10/2004

30/11/1980 25/04/1981 23/06/1983 28/08/1988 21/06/1989 24/06/1991 22/07/1992 11/04/1993 19/04/1994 23/12/1994 29/11/1995 21/11/1996 16/11/1997 18/05/1999 24/01/2000 23/03/2003 10/03/2005 19/05/2006 22/07/2006 19/05/2007 21/11/2007 12/11/2008 Figure 5. 6 Peak river discharge rates from 1980-2008 (DWAF 2009)

Kogmanskloof River Discharge Rate Peaks during Severe Weather Events 5 4.5 4 3.5 3

2.5

DischargeRates 2

1.5

0.5

6/04/1982 2/07/1985 4/07/1996 5/04/1997 8/05/1998 2/07/2001 6/10/2004

25/04/1981 23/06/1983 28/08/1988 21/06/1989 24/06/1991 22/07/1992 11/04/1993 19/04/1994 23/12/1994 29/11/1995 21/11/1996 16/11/1997 18/05/1999 24/01/2000 23/03/2003 10/03/2005 19/05/2006 22/07/2006 19/05/2007 21/11/2007 12/11/2008 30/11/1980 Figure 5. 7 Peak river discharge rates from 1980-2008 (DWAF 2009)

Figures 5.6 and 5.7 show and increase in discharge rates for the Kogmanskloof and Breede river West (Measuring Station to the West of Kogmanskloof tributary). The Breede River and Kogmanskloof show an increase of 83% and 58% respectively.

5.3 Description of Extreme Weather Events 2003 – 2008

5.3.1 Rainfall

Rainfall March 2003

200 180 McGregor 160 140 Rhebokskraal 120 Robertson 100 80 Ashton 60 Montagu Rainfall(mm) 40 Tot-u-Diens 20 0

23 24 25 Date

Figure 5.7a

Rainfall August 2006

200 180 160 McGregor 140 Rhebokskraal 120 Robertson 100 Ashton 80

60 Montagu Rainfall(mm) 40 Tot-u-Diens 20 0 21 22 23 24 Date Figure 5.7b

Rainfall November 2007

200 180 160 McGregor 140 Rhebokskraal 120 Robertson 100 80 Ashton

60 Montagu Rainfall (mm) Rainfall 40 Tot-u-Diens 20 0 20 21 22 Date

Figure 5.8c

Rainfall November 2008

200

180 160 McGregor 140 Rhebokskraal 120 Robertson 100 80 Ashton

60 Montagu Rainfall (mm) Rainfall 40 Tot-u-Diens 20

0 10 11 12 13 Date

Figure 5.8d

Figure 5. 8 Comparative rainfall for severe weather events in 2003, 2006, 2007, 2008 (SAWS 2009)

Figure 5.8a, b, c, d show rainfall across the BRWM in four cut-off low events. The 2003 and 2008 events were of similar intensity, affecting a similar spatial extent.

The 2006 event, whilst not generally high rainfall values, was preceded my heavy rainfall earlier in the month adding to the saturation of the ground and therefore the increase in runoff and extent of the damage.

The 2007 event was concentrated in the Eden District, however there was significantly enough rainfall in the BRWM to cause some damages to infrastructure. During all of these events, significant rainfall is recorded in the McGregor area, however very little damage is sustained.

5.3.2 Peak river discharge rates

Peak River Discharge Rates 16

10 2003 2006 8 2007

Discharge 2008

0 Keiser Breede East Pietersfontien Kogmanskloof Figure 5.9a peak river discharge rates (2003, 2006, 2007, 2008)

Peak River Discharge Rates 1200

1000

800

2003 2006 600 2007

Discharge 2008

400

200

0 Breede West

Figure 5.9b peak river discharge rates (2003, 2006, 2007, 2008)

Figure 5. 9 Comparative peak river discharge rates in the BRWM for severe weather events in 2003, 2006, 2007, 2008 for all hydrological stations (DWAF 2009)

Figure 5.9 a and b show the peak discharge rates of all measured rivers in the BRWM. The Breede River and Pietersfontein River show and increase in discharge rates from 2003 to 2008. The Kogmanskloof River shows a similar discharge rate in 2003 and 2008.

5.4 Risk Exacerbating Factors for Run-off Risk

5.4.1 Land-use/ Land cover

The direct observations of the Hoop, Willem Nels, Droe, Kogmanskloof, Kingna and Keisies Rivers and catchments focusing on land use/ land cover, revealed densely populated wooded alien vegetation in the upper catchment, with severely diminished undergrowth of natural vegetation. The rivers studied, were densely populated with reeds and visible vegetation debris on sand banks in the centre of the rivers.

Agriculture is predominantly viticulture and orchards in close proximity to riverbanks with bulldozing being conducted along riverbanks in order to maximise cultivation area. Riverbanks where in many cases unnaturally steepened due to erosion, especially in urban centres. High levels of siltation could be seen underneath bridges and scouring was present against the riverbanks near most urban areas (See Appendix E.

5.4.2 Wildfire occurrence

Number of Fires and Hectares Burned per Year

2 6 9000 R = 0.0273 2 8000 R = 0.0354 5 7000 4 6000 Number of Fires Per Year 5000 3 Total Hetares per Year 4000 Linear (Total Hetares per Year) Linear (Number of Fires Per Year)

2 3000 Hectares(Ha) Number of Fires of Number 2000 1 1000

0 0

1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 1976 Figure 5. 10 Number of fires and hectares burned per year 1976-2002 (WCNCB 2009)

From figure 5.10 shows the number of wildfires and hectares burned per year from 1976-2002. An increasing trend in the number of fires per year by 21% from 1976–2002 can be observed. The amount of hectares burned per year has increased by 154% from 1976–2002, showing a clear increase in the frequency and spatial intensity of wildfires from 1976-2002. The Langeberg Mountains are situated in a high risk fire area. The natural vegetation has a natural fire cycle in order to germinate. (WCNCB 2009)

5.5 Economic Losses 2003 – 2008

Economic losses for each flood event are normally clustered in five general areas. Losses are specially classified for national government, provincial government local districts and municipalities, as well as private and other sectors.

Total losses for Severe Weather Events

R 1,400

R 1,200 Nat. Govt Dpt R 1,000 Prov. Govt Dept. R 800 Municipalities

R 600

Rnds (Million)Rnds Subtotal for Private and Other Sectors R 400 Total for Event

R 200

R 0 Mar 2003 Aug 2006 Nov 2007 Nov 2008 % Inc 2003- 2008

Figure 5. 11 Departmental dreakdown of economic losses and percentage change from 2003-2008 (Incedent reports 2007, 2008, DiMP 2003, 2007)

Figure 5.10 shows the breakdown of economic losses and percentage increase form 2003 – 2008. The economic losses show only the main departments and cover the costs for the entire flood event across all spatial areas it covered.

Damages Represented in ZAR (Million) Departments March August November 2007 November 2008 Total Average Percentage 2003 2006 losses per Increase 2003- event 2008 National Government Tansnet 5.0 5.0 1.3 DWAF 13.8 2.9 8.9 16.3 41.9 10.5 17.8 SanParks 1.8 10.6 12.4 3.1 SanRal 87.7 1.8 89.5 22.4 Subtotal National Gov 13.8 92.4 24.6 18.1 148.9 37.2 30.8 Provincial Government Housing 28.9 187.5 216.4 54.1 Agriculture 89.6 109.9 178.9 748.3 1126.7 281.7 735.1 Cape Nature (DEAT) 1.1 3.4 8 12.6 3.1 Education 1.7 2.6 4.3 1.1 Provincial Roads 78.6 90.8 408.2 117 694.6 173.7 48.8 Public Works 13 13 3.2 Social Development 1.5 1.4 0.1 3 0.8 -93.8 Emergency Services 0.1 0.1 Health 0.3 0.3 0.1 Subtotal Provincial Gov 172.7 248.6 784.4 865.3 2071 517.7 401.1 All District and Local Municipalities 6.9 103.7 372.5 65.9 549 137.3 851.6 Other Sector Eskom 1.6 1.6 0.4 Spoornet 47.2 47.2 11.8 Telkom 0.7 0.7 0.2 Subtotal Other Sector 1.6 47.9 49.5 12.4 Private Sector SA Insurance Agency 3.2 17.8 21 5.3 Bellair Dam 14 14 3.5 Irrigartion Boards 0.2 0.2 Subtotal Private Sector 17.4 17.8 35.2 8.8 Total 212.4 510.5 1181.4 959.3 2853.6 713.4 346.9

Table 5. 1 Total breakdown of economic losses and percentage change from 2003-2008 (Incedent reports 2007, 2008, DiMP 2003, 2007)

Table 5.1 shows the changing patterns of total loss for the entire area affected by the disaster. For all events, the provincial government shouldered most of the cost. For the 2007 and 2008 events, the private and other sector costs could not be accurately reflected.

Damages represented in ZAR March August November November Average loss percentage Damage 2003 2006 2007 2008 Total per event increase Municipal Roads & Bridges 3,500,000 800,536 68,048 4,132,000 8,500,584 2,125,146 18.1 Provincial Roads 0 5,479,980 2,043,000 12,950,000 20,472,980 5,118,245 136.3 Irrigation 0 0 0 291,000 291,000 72,750 Electrical (Poles & Cables) 387,415 0 0 6,221,178 6,608,593 1,652,148 1505.8 Sewage 686,400 257,964 0 770,000 1,714,364 428,591 12.2 Waterworks and Supply 58,200 0 0 1,340,000 1,398,200 349,550 2202.4 Houses 700,000 0 0 123,000 823,000 205,750 -82.4 Stormwater Drainage 10,000 0 0 10,000 2,500 * Other Municipal Damages 149,000 360,000 0 942,807 1,451,807 362,952 532.8 Total 5,481,015 6,908,479 2,111,048 26,769,985 41,270,527 10,317,632 388.4129151 Table 5. 2 All municipal losses for the BRWM and Provincial Roads (DiMP 2009)

Table 5.2 shows the breakdown of municipal losses for the BRWM as well as losses for provincial roads located in the BRWM.

CHAPTER 6 ANALYSIS

6.1 Introduction

The data gathered during this investigation illustrates rainfall, peak discharge rate and wildfire trends at a municipal scale that has occurred between 1980 -2008. These findings have been analysed with the data collected from the four severe weather events in study and the economic losses to determine correlations, and causes form 2003 -2008.

6.2 Analysis of Municipal Scale Flash Floods and Exacerbating hazard drivers

Trends Beginning End Average Percentage Change in Value Value trend over time (%) Annual Rainfall 1980-2008 Number of event 41 42 44 4.7 Volume of Rainfall (mm) 364 781 540 -5.5 Days of Rainfall 101 108 111 1.8

Severe Rainfall Events 1980- 2008 Frequency per year 1 2 2 53 Volume of Rainfall (mm) 140 175 144 32 Duration 6 6 5.8 -21 Peak River Discharge Rates (1980-2008) Kogmanskloof River (m3/s) 0.2 4.3 1.2 58 Breede River (m3/s) 15 1100 179 83 Wildfires 1976-2002 Hectares Burned per Fire (Ha) 954 50 Number of Fires Per Year 2 1 1.8 33 Hectares Burned per Year (Ha) 200 50 1742 133 Table 6. 1 Summery of trend averages and percentage change over time

Table 6.1 summery all the findings over the past 30 years and shows whether they have increased or decreased over time. There is a slight increase in the number of days of rainfall and number of events per year, but there is a decrease in the amount of rainfall per year. This will have implications on the land use and cover of the area with a change in the rainfall amount and pattern. Less annual rainfall will also have impacts on the runoff and infiltration rates.

The findings show a large increase in total rainfall and frequency of severe weather events and show a decrease in the numbers of days over which rainfall is recorded during these events. This means that more rainfall is falling over fewer days which will increase the intensity of the storms and time between these storms will decrease.

Both the Breede and Kogmanskloof rivers show a massive increase in recorded peak discharge rates during a severe weather event. There could be many reasons for this increase, including alien vegetation, agricultural and urban encroachment,

Fire intensity data up to 2008 was unfortunately not available so data from 1976- 2002 was used and the data given was only for the Langeberg nature reserve. These findings do show a marked increase in wild fires frequency and spatial extent. The causes of this increase are broad and could be from either arson, increased temperatures or increased field burning. One possible theory is that the increase in wild fires is caused in part by the increase in alien vegetation but also the increase in temperatures. The effects of wildfires are a hardening of the surface due to the creation of water impervious soils and an increase in erosion and loss plant material. This could lead to the increase in discharge velocity and debris loading seen in during the four flood events in study.

The finding correlate with the projections of Midgley 2005 and Singleton 2006 in that both papers stated that for the Western Cape: Severe weather intensity and frequency would increase, annual rainfall would decrease and fire frequency and intensity would increase.

6.3 Analysis of Proximal Flash Flood Hazard Conditions for 2003, 2006, 2007,2008

SAWS Month/ Year Weather Station March August November November 2003 2006 2007 2008 Montagu (mm) 243 53 60 133 Robertson (mm) 83 112 65 148 Ashton (mm) 80 88 48 106 Average for specific 135 84 57 129 event (mm) Average for Severe 144 144 144 144 weather events (1980- 2008) Table 6. 2 Total rainfall per severe weather event in mm (SAWS 2009)

Table 6.2 shows the total rainfall to fall at three weather stations in the BRWM for each event. From this, it indicates where the majority of the rain fell and therefore which areas would be the most effected. During the March 2003 flood, Montagu received most of the rainfall, which explains why it received most of the damage and why the losses were focussed in that area and along the Kogmanskloof pass.

The August 2006 event was a combination of two events that cut-off lows, three weeks apart. The second event had the most effect on the BRWM, and that effect was focused mainly in the Robertson area. The reason that the cost of this event was as high as the 2003 event could have been due to the fact that the ground was already saturated from the previous less severe event.

The November 2007 event did not have a significant effect on the BRWM in comparison to the other three events, and rainfall was far lower then the average for severe weather events. However it did have a large impact to the East of the BRWM.

The November 2008 event had a similar spatial extent and severity as the March 2003 event but was far more devastating in terms of cost. The possible reason for this could be a thunderstorm recorded in the karoo the day before the event caused the Keisies to be in flood and when this was combined with the cut-off low, the runoff was escalated. Another factor that could have caused the escalation in damages was the fact that the rainfall was more dispersed during this event and not only focused on Montagu but also Robertson.

6.4 Analysis of Adjusted economic losses

Damages represented in ZAR Percentage March August November November Average loss increase Damage 2003 2006 2007 2008 Total per event 2003-2008 Municipal Roads & Bridges 2,882,799 564,465 44,514 2,455,788 11,992,361 2,998,090 -15 Provincial Roads 0 3,863,982 1,336,436 7,696,623 25,673,397 6,418,349 99 Irrigation 0 0 0 172,951 291,000 72,750 Electrical (Poles & Cables) 319,097 0 0 3,697,457 6,927,690 1,731,922 1059 Sewage 565,358 181,892 0 457,637 2,461,614 615,403 -19 Waterworks and Supply 47,937 0 0 796,407 1,446,137 361,534 1561 Houses 576,560 0 0 73,103 1,399,560 349,890 -87 Stormwater Drainage 0 7,051 0 0 17,051 4,263 * Other Municipal Damages 122,725 253,839 0 560,342 1,828,371 457,093 357 Total 4,514,475 4,871,229 1,380,950 15,910,309 52,037,181 13,009,295 252

Table 6. 3 Municipal adjusted losses and provincial roads 2003-2008

Damages represented in ZAR Department March 2003 August 2006 November 2007 November 2008 Total Nat. Govt Dpt 11.4 65.2 16.1 10.7 103.3 Prov. Govt Dept 142.2 175.3 513.1 514.3 1344.9 ALL District and Local Municipalites 5.7 73.2 243.7 39.1 361.7 Subtotal for Other Sectors 1.3 33.8 0.0 0.0 35.1 Total for Event 175.0 359.9 772.8 564.2 1871.9

Table 6. 4 All adjusted losses for flood events 2003-2008 (Incedent reports 2007, 2008, DiMP 2007, 2003)

Table 6.3 shows a significant increase in municipal losses for the BRWM over time with the majority of losses being associated to roads and bridges. There does appear to be a decrease in the losses associated with municipal roads and bridges, while provincial roads losses have increased by nearly one hundred percent. The reason for this is unclear due to the lack of specific road geo referencing. Another anomaly to be explained is the fact that the losses for the BRWM in 2006 were similar to that of 2003, even though the rainfall average was much less.

Table 6.4 shows an increase across all sectors. The most significant increase is that of the provincial government, while the national government is paying less when comparing all events.

Max total Adjusted total Adjusted municipal Roads and bridges rainfall municipal losses for roads & bridges and as a percentage of (mm) the BRWM (ZAR) provincial roads for the total losses (%) BRWM (ZAR) March 2003 243 4,514,475 2,882,799 64 August 2006 123 4,871,229 4,428,446 91 November 2007 108 1,380,950 1,380,950 100 November 2008 160 15,910,309 10,152,411 72 Ave Rainfall – 144 Severe Weather Events Percentage -32 252 252 increase 2003- 2008

Table 6. 5 Comparison of maximum rainfall and adjusted total municipal and public infrastructure losses

Table 6.5 shows a comparison of the total rainfall per flood event and the total municipal losses and the municipal public infrastructure losses. Total rainfall tends to be decreasing with time, while total losses and infrastructure losses have increased by 252%. Infrastructure also accounts for the highest percentage of total municipal losses and therefore would appear to be the most affected by and costly consequence of severe weather events.

Correlation Total Adjusted Municipal Adjusted Municipal Losses Infrastructure Losses Max Rainfall 0.14 0.04

Table 6. 6 Correlation between maximum rainfall and economic losses

Table 6.4 shows the correlation between maximum rainfall and municipal and infrastructural losses from 2003 to 2008. The correlation is very weak and therefore indicating that rainfall is not the only factor associated with escalating economic cost of severe weather events.

It also indicates that between 2003 and 2008, that rainfall has not followed the 1980- 2008 climate trends and the total rainfall during these events has decreased rather then increased. This finding is important as it underlines the climatic variability of different spatial scales especially when looking at a small spatial and temporal scale. This study also indicates that rainfall is not the only aspect associated with damage during a severe weather event and that losses should be attributed to both anthropogenic and natural factors.

6.5 Severe Rainfall Effects Analysis in Relation to Climate Change

The findings above relate very closely to the projections made by Midgley 2005 and Singleton 2009. In that they predicted the increasing severity and frequency of cut-off lows over the South Africa and in particular over the Western Cape. Unfortunately due to inaccurate data from DWAF it is impossible to know the actual trends of discharge rates but they do show an increase in discharge over the past thirty year and it is believed that data capturing was more efficient in the past. This therefore shows that for rainfall and discharge is during severe weather events are increasing with time as projects have shown. However when looking at the four events in study, it would appear that the rainfall is decreasing and their, with inaccurate discharge rates it is difficult to assign responsibility for the increase in economic losses. If we take the increase in discharge rates over time to be correct and therefore these four events have had an increase in discharge rates, and the cause for this increase in discharge is not rainfall, then one need’s to look at the hazard drivers on different scales to determine causation.

Other aspects that may influence the increase economic cost of severe weather events due to climate change are the increase in hard surfaces due to increased temperature and the increase in Orographic rainfall which means that more of the rainfall is falling at a higher altitude and would therefore explain the decrease in rainfall seen at the current SAWS weather stations in the low lying urban areas. This increase in Orographic could also cause an increase in the discharge velocity thereby increasing the damage caused to infrastructure.

6.6 Current Management Strategies and Solutions

Currently the management of the Breede River catchment falls under the Breede Overberg Catchment Management Agency (BOCMA). A recent strategy has not been publicly released by BOCMA so the management assessed in this thesis is the National Water Resource Strategy, Water Management Area 18: Breede River. This document was released in 2004 and is still relevant to issues present today. The strategy does show and integrated and holistic approach to managing the catchment, the challenges arise in the implementation of these strategies and the cooperation between departments (NWRS 2004).

The observed current solutions to infrastructural failure include the repairing and reinforcing of roads and bridges. River banks are being reinforced by gabion retainers to decrease erosion and maintain the current river channel (IDP 2009). The current strategy at the present leans more towards recovery then mitigation as more emphasis and money is placed on making water available to people, agriculture and possible future transfer schemes then disaster mitigation (NWRS 2004).

CHAPTER 7 DISCUSSION AND RECOMMENDATIONS

7.1 Introduction

Flooding in the BRWM has and will continue to cause damage to public infrastructure with an increasing cost of recovery in the future. The causes for this increasing level of destruction are anthropogenic and nature, and are highly complex and interconnected. Responsibility cannot be attributed to one factor as all forcing factors act to the increasing vulnerability of infrastructure. The management of the catchment must therefore be integrated with a holistic approach. The cooperation of all key stakeholders is vital.

7.2 Managerial Recommendations

The two most damaging forces during a flood event are the velocity of the river discharge rates and debris loading. Reducing these two factors could assist in reducing the vulnerability of infrastructure downstream.

Possible recommendations to assist in the reduction of runoff during a severe weather event could be the removal of all alien vegetation in the riparian zone and the restoration of the natural riparian vegetation and river banks. This will create a buffer zone to slow the runoff. Similarly a limitation should be enforced to ensure cultivation and construction is not performed in the natural riparian zone (NWRS 2004).

Due to the uncertainty of future predictions for climate variability, the possible changes in land use and cover are unknown. Therefore any further construction and development in the BRWM needs to take the most accurate climate variability predictions into account when planning development. The Western Cape and especially the fast growing Cape Town Metropolitan will likely suffer from severe water limitations in the future with the reduction in annual rainfall and the increasing population. Therefore possible transport schemes of water out of the BRWM may be necessary. This possible reduction in water availability needs to be taken into consideration for future development and riverine management (NWRS 2004).

DWAF has released a highly competent strategy with the NWRS in 2004 which covers many integrated and holistic approaches to dealing with the impacts of climate change and anthropogenic forces on the water availability. Many of the recommendations for increasing the water availability are the same recommendations given for reducing infrastructure vulnerability. The challenge of the implementation of these recommendations comes in the form of costs, skills and cooperation between departments (NWRS 2004).

Bridge infrastructure will always be vulnerable to severe weather events. For some of the bridges and causeways in the urban areas it may be impossible to redesign and rebuild due to the costs and practicalities. Currently many bridges are being reinforced with concrete and river banks will gabions. It is still unclear as to weather these techniques will be successful but they are currently the only options for municipal engineers.

7.3 Research Recommendations

Many climate change reports predict an increase in higher altitude rainfall across the Western Cape and a decrease on the lower level plains (Midgley 2005). Climate change predictions are well known for larger areas such as the whole of the Western Cape but predictions on a local level are also very important. Therefore in a mountainous region like the BRWM further research into the changing rainfall patterns and the increase in high altitude rainfall are vital for flood prevention planning.

There is a poor understanding of future changes in land use and cover due to climate change and therefore future research into understanding how farmers may react to climate change is vital. The change in vegetation cover, alien vegetation and fire patterns will also need to be further researched to assist in the prevention of increased runoff and debris loading. Further studies into the hydrology of the small rivers running through the towns and the tributaries of the Breede are important because at present the data for even the larger rivers is incomplete. It is therefore vital to gain an understanding of the river behaviour before committing to a restoration programme that may not be best suited to the river.

The research into making public infrastructure more resilient to flooding is important as the economic cost of recovery increases with every flood event, it should be prudent to spend more money on mitigation now and less on long-term recovery.

REFERENCES

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Department of Water Affairs and Forestry, South Africa. 2003. Invasive Alien Plants. Prepared by J Larson and W Karnish of Ninham Shands (Pty) Ltd in association with MBB Consulting Engineers and Jakoet & Associated as part of the Breede River Basin Study. DWAF Report P H 00/00/2002

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Appendix A General Geographic Characteristics

Figure 1A Annual rainfall distribution across the BRWM. Rainfall tends to increase with altitude (Ninham Shands 2003)

Figure 2A Distribution of veld types. Sclerophyllous and False Sclerophyllous bush types are dominant in the Langeberg mountains which are highly infested with aliens and have a high fire risk (www.agis.agric.za/agisweb/agis.html).

Figure 3A Shows the areas most susceptible to erosion are in the higher altitude, especially in the Langeberg mountains which are highly infested with aliens and have a high fire risk (www.agis.agric.za/agisweb/agis.html)

Figure 3A Underlying Geology of the BRWM (Ninham Shands 2003) Figure 4A Lithology of BRWM (Ninham Shands 2003)

Appendix B Land Use/ Land cover and Wildfires

Figure 1B Basic land cover in the BRWM. Light blue and green are cultivated. The heaviest cultivation is along the Breede River and other tributary catchments (www.agis.agric.za/agisweb/agis.html)

Figure 2B Farming areas. Red shows irrigated area which is concentrated in the riverine areas. Almost all area has bee demarcated to farming (www.agis.agric.za/agisweb/agis.html) 61

Figure 3B Tree density is concentrated to the higher altitudes and riverine areas. Many of these trees are aliens or plantations. (www.agis.agric.za/agisweb/agis.html)

Figure 4B The fire risk areas are concentrated in the higher attitudes and Breede river valley. The highest fire risk area is in the upper catchments in the Robertson area. This could cause an increase in the runoff of the Hoop, Droe and Willen Nels rivers into Robertson (www.agis.agric.za/agisweb/agis.html) 62

Figure 5B Land use/ Cover in the Robertson area. Cultivation is taking place very high in the catchment of the rivers in the Langeberg Mountains and Alien infestation is prevalent in the upper catchments. (Ninham Shands 2003)

Figure 6B Land-use/ Land cover in the Ashton Area. The Kogmanskloof and Langeberg Mountain show high levels of infestation along the riparian zones of the rivers (Ninham Shands 2003).

Figure 7B Land-use/ Land cover in the Montagu Area. Cultivation is intense along both the Keisies and the Kingna Rivers. Alien vegetation appears to be low. The path of the rivers is slightly distorted to the North due to the scale of the map (Ninham Shands 2003)

Appendix C Exposed Infrastructure

Red = Exposed Infrastructure Green = Agriculture in upper catchments

Robertson Area

Figure 1C Infrastructure exposed along the Hoop, Droe and Willem Nels River, through the urban centre of Robertson. There is intense agriculture along all of these rivers in the upper catchments. (www.agis.agric.za/agisweb/agis.html)

Ashton Area

Figure 2C Exposed infrastructure along the Kogmanskloof pass. (www.agis.agric.za/agisweb/agis.html)

Montagu Area

Figure 3C Exposed infrastructure along the Keisies and Kingna River which merge to form the Kogmanskloof River. Montagu has the potential to be split in three during a flood event (www.agis.agric.za/agisweb/agis.html) 67

Robertson

Figure 4C Shows exposed infrastructure in Robertson and where photographs were taken. Many of the river crossing are causeways and therefore have to potential to be cut with every large rainfall event. Robertson can also effectively be cut off to the East when the Willem Nels River floods the R60 access root. (Map Studio)

Montagu

Figure 5C Shows exposed infrastructure and photographs taken. The areas circled twice show areas of extreme exposure. These include the Avalon Springs Resort which suffered large losses during the 2008 event and the Voortrekker bridge which is situated in a shallow valley with very low clearance above the water, at the converging point of two rivers. (Map Studio)

Appendix D Field Photographs

Photos Numbered according to figures 4C and 5C

Photo 1 Kogmanskloof pass. The road is situated very close to the river and not elevated above the flood plain. The narrowness of the valley means that discharge velocity could be high in the Kogmanskloof River especially due to the fact that it is a combination of the Kingna and Keisies Rivers by this stage. (not on map)

Photo 2 The Voortrekker Bridge. Kingna runs underneath whilst the Keisies runs on the left behind the man made barrier. The clears between the

water and the bridge is very small and mush of the underneath of the bridge is silted up by debris.

Photo 8 wooded Alien infestations in the Riparian zone of the Kinga river in Montagu

Photo 13 The proximity of agriculture on the right to the Kogmanskloof River in Ashton. The fruit canning factories on the left have been damaged during many of the floods

Photo 19 Shows the close proximity of urban structures to the Hoop River in Robertson and the ultimate consequences

Photo 26 The current management solution of reinforcing the riverbanks to stop erosion could have the effect of increasing discharge rates due to the canalization of river and lack of a buffer zone.

Photo 27 River bank steepening due to erosion and alien vegetation.

Photo 21 Current management solution which involves the reinforcing of bridges with concrete and stones on either side of the bank