TRANSNET SOC LTD FEASIBILITY STUDY (FEL 3) FOR …€¦ · FEASIBILITY STUDY (FEL 3) FOR THE DEEPENING OF . BERTHS 203 TO 205 . PORT OF DURBAN . DESIGN REPORT – ... level in all

TRANSNET SOC LTD

FEASIBILITY STUDY (FEL 3) FOR THE DEEPENING OF

BERTHS 203 TO 205

PORT OF DURBAN

DESIGN REPORT –

EFFECTS OF CLIMATE CHANGE ON ENGINEERING DESIGN

ZAA 1370 | RPT | 028 REV F

23 January 2014

TRANSNET SOC LTD FEASIBILITY STUDY (FEL 3) FOR THE DEEPENING OF BERTHS 203 TO 205

PORT OF DURBAN DESIGN REPORT – EFFECTS OF CLIMATE CHANGE ON ENGINEERING DESIGN

ZAA 1370 | RPT | 028 Rev F January 2014

REVISIONS

REV DATE DESCRIPTION DESIGNED

BY CHECKED

BY APPROVED

BY

A 09 November 2012 Issued for Comment CJE JZ JZ

B 16 November 2012 Updated CJE JZ JZ

C 07 June 2013 Update after Client Review CJE MC JZ

D 27 June 2013 Additional References cited CJE JZ JZ

E 22 November 2013

Revised to address comments by Department of Environmental

Affairs – Issued for client review

CJE/MC MC/SZH/JZ JZ

F 23 January 2014 Revised to address comments by

Department of Environmental Affairs – Issued for use

CJE/MC MC/SZH/JZ JZ

AUTHORISATION

AUTHORISED BY NAME SIGNATURE DATE

DIRECTOR J ZIETSMAN

23 January 2014

This document, including all design and information therein, is Confidential Intellectual Property of ZAA Engineering Projects and Naval Architecture (Pty) Ltd.

Copyright and all other rights are reserved by ZAA Engineering. This document may only be used for its intended purpose.




CONTENTS

1.0 INTRODUCTION ....................................................................................................................................... 1

1.1 Background to report ...................................................................................................................................... 1 1.2 Project Background ......................................................................................................................................... 1 1.3 Scope of report ............................................................................................................................................... 1

1.3.1 Establishment of climate change affected parameters ................................................................. 1 1.3.2 Design impacts .............................................................................................................................. 2 1.3.3 Construction phase ....................................................................................................................... 2 1.3.4 Risk mitigation ............................................................................................................................... 2

2.0 CLIMATE CHANGE AFFECTED PARAMETERS ............................................................................................. 3

2.1 Design Approach ............................................................................................................................................. 3 2.2 Sea Level Rise .................................................................................................................................................. 3

2.2.1 Historic .......................................................................................................................................... 3 2.2.2 The South African Context............................................................................................................. 4 2.2.3 Global Sea Level Rise Predictions .................................................................................................. 4

2.2.3.1 Intergovernmental Panel on Climate Change ............................................................................... 4 2.2.3.2 UK Climate Projections Report June 2009 ..................................................................................... 6

2.2.4 Project Design Criteria ................................................................................................................... 6

2.3 Wind ................................................................................................................................................................ 7

2.3.1 Global Predictions ......................................................................................................................... 7 2.3.2 Project Design Criteria ................................................................................................................... 8

2.4 Storm Surge..................................................................................................................................................... 8

2.4.1 Project Design Criteria ................................................................................................................... 8

2.5 Other parameters ........................................................................................................................................... 8

2.5.1 Temperature ................................................................................................................................. 8 2.5.2 Rainfall ........................................................................................................................................... 9 2.5.3 Ocean Acidification........................................................................................................................ 9

3.0 IMPACTS ON DESIGN ............................................................................................................................. 10

3.1 Selection of cope level taking into account sea level rise and storm surge .................................................. 10

3.1.1 Predicted Water Levels to 2069 .................................................................................................. 10 3.1.2 Sensitivity Analysis – Predicted Water Levels at 2100 ................................................................ 11

3.2 Structural design of new quay walls and quay furniture .............................................................................. 11 3.3 Storm water system ...................................................................................................................................... 11 3.4 Concrete design for durability ....................................................................................................................... 11

4.0 IMPACT DURING CONSTRUCTION PHASE............................................................................................... 13

5.0 MITIGATION OF RISKS IN CONSTRUCTION AND OPERATIONAL PHASES ................................................. 13

6.0 CONCLUSION ......................................................................................................................................... 13

7.0 REFERENCES .......................................................................................................................................... 15

ANNEXURE ADDITIONAL REFERENCES ............................................................................................................ 1




GLOSSARY OF TERMS This section provides definitions of terms, symbols and acronyms used in this report. Chart Datum The plane or level to which water elevations (or depth soundings) or tide heights are referenced.

In Durban, Chart Datum is defined by the SA Navy Hydrographer as 0.913 metres below Land Levelling Datum. Chart Datum is the Lowest Astronomical Tide (LAT) level in all ports in South Africa. However it is defined by TNPA as 0.9 metres below this level (Chart Datum Port). The reference level referred to in this report is Chart Datum Port (CDP).

Climate Change Climate change as defined by IPCC usage refers to a change in the state of the climate that can be identified (e.g. using statistical tests) by changes in the mean and/or the variability of its properties, and that persists for an extended period, typically decades or longer. It refers to any change in climate over time, whether due to natural variability or as a result of human activity. This usage differs from that in the United Nations Framework Convention on Climate Change (UNFCCC), where climate change refers to a change of climate that is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and that is in addition to natural climate variability observed over comparable time periods.

Cope Level Level of the top of the quaywall relative to CDP.

Cyclone An atmospheric system characterised by rapid inward circulation of air masses about a low pressure centre. Cyclones are usually accompanied by very high speed winds and stormy, destructive weather. Cyclones circulate counter-clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.

Design Life The Design Life of a structure or facility is the Useful Life (Economic Life) of that entity (in this case 50 years), at a required level of service.

Fetch The area within which Seas are generated by a wind having a fairly constant direction and speed. Fetch is sometimes used synonymously with Fetch Length.

HAT Highest Astronomical Tide level

IAP Interested and Affected Party during the Environmental Impact Assessment (EIA) process.

IPCC Intergovernmental Panel on Climate Change.

LAT Lowest Astronomical Tide level.

ML ML (Mean Level) is the mean of the heights of MHWS, MHWN, MLWS, MLWN.

MHWS Mean High Water Springs.

MHWN Mean High Water Neaps.

MLWN Mean Low Water Neaps.

MLWS Mean Low Water Springs.

Neap Tide A tide occurring near the time of quadrature of the moon with the sun. The neap tidal range is normally between 10% and 30% lower than the mean tidal range.

Pressure Deficit Pressure Deficit is the atmospheric pressure reduction resulting from a high wind due to causes such as a cyclone (hurricane). This causes a vertical rise in water level that contributes to Storm Surge.

PRDW Prestedge Retief Dresner Wijnberg Pty Ltd - consulting port and coastal engineers.




RCP Representative Concentration Pathways adopted by the IPCC for its Fifth Assessment Report (AR5). These describe four possible future climate scenarios based on greenhouse gas concentration trajectories.

Seas Waves caused by wind at the time and place of observation.

Ships Waves Ships Waves are waves generated by a vessel such as a ship or boat moving through the water.

SLR Long term vertical Sea Level Rise caused by long term Climate Change effects.

Spring Tide A tide that occurs at or near the time of a new or full moon and which rises and falls the highest and lowest respectively above and below Mean Sea Level.

Still Water Level Still Water Level is the vertical level of the water surface (in metres) relative to Chart Datum, in the absence of waves.

Storm Surge The term Storm Surge describes the rise above normal water level on an open coastline due to the action of wind stress on the water surface. Storm surge resulting from a cyclone also includes the vertical rise in water level due to atmospheric pressure reduction (Pressure Deficit), as well as that due to wind stress. In this report Storm Surge is deemed to also include Wave Setup.

Swell Wind generated waves that have travelled out of their generating area. Swell generally exhibits a more regular and longer wave period and has flatter crests than waves within their fetch. The latter waves are known as Seas.

Tide The Tide is the periodic rising and falling of the water that results from gravitational attraction of the moon and sun and other astronomical bodies acting on the rotating earth.

Tidal Range Difference in height between consecutive high and low water levels.

TNPA Transnet National Ports Authority.

Waves An undulation of the surface of a body of water such as the ocean or estuary.

Wave Amplitude Wave Amplitude is height of the water surface level above or below the still water level. The maximum Wave Amplitude is approximately equal to half the Wave Height. This is true for linear waves, but not for non-linear waves.

Wave Crest Wave Crest is the highest part of the wave above Still Water Level.

Wave Trough Wave Trough is the lowest part of the wave below Still Water Level, between successive Wave Crests.

Wave Height The vertical distance between the Wave Crest and the preceding Wave Trough.

Wave Length The horizontal distance (metres) between successive wave crests (or troughs).

Wave Period The time (in seconds) for a wave to traverse a distance equal to one Wave Length.

Wave Setup Wave Setup is the vertical increase of the water surface, over and above normal surge elevation, caused by the onshore mass transport of water by wave action alone.

Wind Setup The term Wind Setup describes the vertical rise in water level on the leeward side of a body of water due to wind stresses on the surface of the water.

Wind Waves Waves which are formed and generated by the wind.



ZAA 1370 | RPT | 028 Rev F January 2014 Page | 1

1.0 INTRODUCTION

1.1 Background to report

This report explains the basis of the approach that has been adopted in the Project Design Premise to account for the effects of long term climate change on the marine engineering design of the proposed Berth 203 to 205 Berth Deepening Project at Pier 2 in the Port of Durban. The report was originally produced in response to a query raised by an Interested and Affected Party (IAP) during a public meeting which was part of the Environmental Impact Assessment (EIA) process. The EIA process and the application for a Record of Decision (ROD) to authorise the project are vital components of the planning and execution of this upgrade project.

The report has been modified in different revisions in order to explain the content in greater clarity as a result of additional queries and comments from other IAPs. This Revision F has been rephrased in order to make it more understandable to the general public. It is emphasised that it has not been necessary to change the Basis of Design in any way as a result the EIA process. This Revision F of the report contains no modified information, other than that obtained from papers and reports published since earlier revisions of this report. The report further addresses the issues raised by the Department of Environmental Affairs in its letter Ref 14/12/16/3/3/2/275 signed on 21 October 2013 issued in response to the initial EIA Report.

The report does not purport to be a research paper on the subject of climate change and sea level rise (SLR). The report reviews and summarises the available literature relating to parameters affected by climate change that are relevant to the marine engineering design for this project. A list of material that has been reviewed is contained in Section 7.0 and in the Annexure. 1.2 Project Background

This report has formed part of the FEL3 level design being undertaken by ZAA for the proposed deepening and upgrading of Berths 203 to 205, Pier 2, Durban Container Terminal. The current block-work quay walls of Berths 203 to 205 were designed in the 1970s to support 4 tonne dockside cranes and have subsequently been fitted with Ship to Shore (STS) container cranes. Recent studies on the stability of the existing quay walls have shown that the factor of safety of Berths 203 to 205 is less than the required industry standard indicating the risk of potential quay wall failure. In addition, vessel sizes that need to be accommodated at the port continue to increase. The proposed project aims to upgrade and deepen the berths such that the factor of safety for the berths meets industry standards and such that the berths can accommodate Post-Panamax container vessels up to 12,000 TEU (fully laden) and 14,000 TEU (partially laden). This will be achieved by the construction of a new caisson wall offset approximately 48m seaside of the existing block-work wall and the simultaneous dredging of the basin and berths adjacent to Pier 2.

1.3 Scope of report

1.3.1 Establishment of climate change affected parameters

The report reviews and summarises the available literature relating to parameters affected by climate change. The parameters listed below are those that can be affected by climate change and are relevant to the marine engineering design. These parameters have been taken into consideration in the design of the proposed quays and associated dredging works:

• Long term sea level rise • Storm surge (wind setup, pressure deficit, wave setup) • Temperature

• Wind (including tropical cyclones)

• Currents • Waves




• Rainfall • Ocean acidification

This report concentrates on the relevant parameters where the effect of climate change would have a significant effect on the design.

1.3.2 Design impacts

Various components of the design are affected by the above listed parameters. The report summarises the impacts of the climate change affected parameters on the design of these components. The various components affected are:

• Selection of cope level for new quays - An important aspect of the design of a quaywall is to establish a safe level for the top of the quaywall (the cope level). This report explains how the design has more than adequately taken account of sea level rise in terms of the reports published by recognised international experts.

• Structural design of new quay walls and quay furniture • Storm water management plan • Concrete design for durability

1.3.3 Construction phase

The report investigates the possible effects of climate change on the project during the construction phase.

1.3.4 Risk mitigation

The report contains a risk mitigation summary which details potential risks to the project due to climate change, together with possible mitigation measures.




2.0 CLIMATE CHANGE AFFECTED PARAMETERS

2.1 Design Approach

The design approach adopted to account for effects of climate change has been to first calculate current design parameters based on statistical analysis of historical data and to then increase these parameters to account for climate change. The recommended increase values have been evaluated and calculated and are presented in Section 2.2 to 2.5 below. The specified Design Life for the new marine structures for this project is 50 years and therefore, with an expected project completion date of 2019, the climate change increase values calculated are for those predicted to the year 2069 (i.e. 2019 + 50). The majority of literature provides predictions for 2095 - 2100 and therefore a form of interpolation / extrapolation is generally required to predict 2069 values. A sensitivity analysis assessing the design against the predicted 2100 values has also been carried out. Due to the uncertainties associated with climate change predictions, the majority of specialist climate change assessment reports referenced generally provide a range with lower bound (5%), central and upper bound (95%) values. Our recommended design approach has been to use the upper bound (conservative) value for the design criteria. 2.2 Sea Level Rise

2.2.1 Historic

Sea level has changed greatly over history and reached a level of about 120 meters below current sea level at the Last Glacial Maximum 19,000-20,000 years ago. Last Glacial Maximum refers to a period in the Earth's climate history when ice sheets were at their maximum extension, between 26,500 and 19,000–20,000 years ago, marking the peak of the last glacial period. During this time, vast ice sheets covered much of North America, northern Europe and Asia. Melting of the ice sheets during the Holocene Period, (generally accepted to have started approximately 12,000 years BP (before present day), caused sea levels to rise, but climate has been fairly stable over the Holocene and the graph (Figure 3.1.1.1) indicates minimal change over the last 4,000 years. There has been approximately 0.17m of sea level rise in the 20th century and an accelerating trend is predicted in the 21st century.

Figure 3.1.1.1- Changes in sea level during the Holocene1 Period

1 Source: Figure prepared by Robert A Rohde from published data and is incorporated into the Global Warming Art Project




2.2.2 The South African Context

Before proceeding with predicting long term sea level rise values based on global research papers and reports, we need to establish the relevance of these global trends to South Africa. Comparisons between Sea Level Rise for Southern Africa (based on approximately 30 years of South African tide gauge records) and global tide gauge records, show substantial agreement with global trends (Mather, 2008). Linear and nonlinear sea-level changes at Durban, South Africa have been reported on by A.A. Mather, (Coastal and Catchment Policy, Co-ordination and Management, eThekwini Municipality), in which the tide records between 1970 and 2003 for Durban, South Africa, have been analysed to determine the extent of recent linear and nonlinear sea level trends in the light of predicted global sea-level rise. The linear trends of monthly mean sea level revealed a sea level rise of 2.7 mm ± 0.05 mm / year and the yearly mean sea-level trend revealed a rise of 2.4 mm ± 0.29 mm / year. Nonlinear trends varied between –1 mm and +8 mm / yr. These findings are similar to recently published results of global sea level rise calculations over the last ten years derived from worldwide tide gauge and TOPEX / Poseidon altimeter measurements, which range between 2.4 mm and 3.2 mm / year.

It can thus be concluded that the local South African rate of Sea Level Rise falls within the range of global trends and for long-term design purposes the global sea level rise projections (refer to section 2.2.3 below) are directly applicable to South Africa. It is noted that an analysis of tide gauge records around South Africa (Mater et al, 2009) revealed a minor variation in regional sea level trends (west coast vs. east coast) however these are considered relatively minor in comparison to uncertainties in the long term global predictions.

2.2.3 Global Sea Level Rise Predictions

Numerous research and studies relating to sea level rise predictions have been published by various recognised organisations in the past decade. The predictions for sea level rise by 2100 vary from a lower limit of 0.15m to an upper limit of 1.9m.

2.2.3.1 Intergovernmental Panel on Climate Change

The Intergovernmental Panel on Climate Change (IPCC), jointly established by the World Meteorological Organisation (WMO) and the United Nations Environmental Programme (UNEP) in 1988, is generally regarded as the primary consensus reference for sea level rise. The various assessments and reports published by the IPCC are therefore used as the basis of design for sea level rise predictions for this project. The latest assessment report published by the IPCC is the IPCC’s 4th assessment report (IPCC, 2007). The AR4 projections of global average sea level rise for 2095 (relative to the baseline of 1980-1999) lie in the range 0.18 m to 0.59m. AR4 expressed low confidence in ice sheet loss estimates generally, recommending a “scaled-up ice sheet discharge” allowance as a precautionary measure, with a nominal range of 0.1 m to 0.2 m on top of the above range, raising the upper estimate to 0.79 m. An unofficial, presumably leaked preliminary version of the IPCC 5th assessment report (AR5) can be found on the internet however the leaked IPCC report contains the stipulation that it may not be cited, quoted nor referenced and we respect this request. However in 2013, Working Group 1 Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change was published as “Climate Change 2013, The Physical Science Basis, Summary for Policy Makers”, (ref. 16). The sea level rise parameters for this project are based on the guidelines and recommendations from this recently released report. IPCC Climate Change 2013, Ref (16), reports that global mean sea level will continue to rise during the 21st century. The IPCC adopted Representative Concentration Pathways (RCPs) this report and these describe four possible future climate scenarios based on greenhouse gas concentration trajectories. Under all RCP scenarios, the rate of sea level rise will very likely exceed that observed during 1971 to 2010 due to increased ocean warming and increased loss of




mass from glaciers and ice sheets (see Figure SPM.9). The extracts below from the report explain the report’s findings on sea level rise in further detail.

• Confidence in projections of global mean sea level rise has increased since the AR4 because of the improved physical understanding of the components of sea level, the improved agreement of process-based models with observations, and the inclusion of ice-sheet dynamical changes.

• The basis for higher projections of global mean sea level rise in the 21st century has been considered and it has been concluded that there is currently insufficient evidence to evaluate the probability of specific levels above the assessed likely range. Many semi-empirical model projections of global mean sea level rise are higher than process-based model projections (up to about twice as large), but there is no consensus in the scientific community about their reliability and there is thus low confidence in their projections.

• Sea level rise will not be uniform. By the end of the 21st century, it is very likely that sea level will rise in

more than about 95% of the ocean area. About 70% of the coastlines worldwide are projected to experience sea level change within 20% of the global mean sea level change.

The IPCC Climate Change 2013, Ref (16) predictions for Global Mean Sea Level Rise to the year 2100 ranges from 0.26m to 0.82m for the various RCP scenarios. For RCP8.5, the worst case scenario, a likely range of 0.45m to 0.82m is predicted by 2100. Table SPM2 below extracted from IPCC Climate Change 2013 shows the predicted sea level rise ranges for the various RCPs.




Extracts From Table SPM2 - Projected Changes in Global Mean Surface Air Temperature and Global Mean Sea Level Rise for the Mid and Late 21st Century, Relative to the Reference Period 1986-2005 (12.4, Table 12.2, Table 13.5, in Ref 16)

2.2.3.2 UK Climate Projections Report June 2009

The UK Climate Projections Report June 2009 (UKCP09) states that “there is a lack of current scientific understanding of some aspects of ice sheet behaviour and as such there are known limitations to including this component in sea level projections” In response, the report provided a High-plus-plus (H++) scenario for sea level rise in addition to the main scenarios which were based on IPCC AR4 predictions. The top of the H++ scenario range was derived from indirect observations of sea level rise in the last interglacial period, at which time the climate bore some similarities to the present day, and from estimates of maximum glacial flow rate. The low probability H++ sea level rise range defined in the report is 0.93 m to 1.9 m by 2100. The report concludes that the upper bound H++ scenario is beyond the likely range but within physical plausibility and that such a scenario might be useful for vulnerability testing over and above the standard UKCP09 uncertainty range, and for getting users thinking about the limits to adaptation. The upper bound H++ scenario has been considered for future contingency planning.

2.2.4 Project Design Criteria

The upper bound predictions (both in terms of worst case scenario RCP and the upper bound value within the RCP8.5 range) from Ref (16), Climate Change 2013, Physical Science Basis, Summary for Policy Makers, serves as the basis for design for this project. This is in agreement with IPCC AR4 together with the scaled up ice sheet discharge, projected from 2095 to 2100. Figure 3.2 shows a plot of the IPCC AR4 sea level rise 2095 values using the IPCC 2001a 3rd assessment report projection graphs. IPCC AR4 does not provide the projected sea level rise over time, only for the year 2095. Therefore the 3rd assessment report projections have been rescaled to match the new AR4 2095 values and the Climate Change 2013 Summary for Policy Makers, Ref (16) values, in 2100. The design life of the structures is until 2069 and using the 95% upper bound envelope, a sea level rise value of 0.48m is predicted. Although the rate of change is expected to increase over time (as shown by the parabolic shape of the 95% envelop on Figure 3.1.4.1 above), due to the uncertainties associated with the rate of increase and to be conservative, we have assumed a linear increase between 1990 and 2100. Therefore a value of 0.58m in 2069 has been conservatively adopted for the design criteria for the project.




Figure 3.2: 1990 to 2100 sea level rise projections (after IPCC, 2001b; 2007b)2 with IPCC (2013) Climate Change

2013, The Physical Science Basis, Summary for Policy Makers Ref (16) 0.82 metres at 2100 Whilst the probability of extreme sea level rise as estimated for example by the UKCP09 H++ scenario is extremely low and it would be irrational and ultra conservative to design large coastal structures to accommodate these levels, the probability of this extent of sea level rise cannot be ruled out completely and these values should be used for future contingency planning i.e. the design should be evaluated for future design adaptions or contingency planning in the event of these extreme scenarios.

2.3 Wind

2.3.1 Global Predictions

There is generally low confidence in predictions of future wind speed changes. Several model studies have suggested increased average and/or extreme wind speeds but some studies point in the opposite direction. The changes in both average and extreme wind speeds may be seasonally variable, but the details of this variation appear to be model-dependent. IPCC predicts that future tropical cyclones will likely become more severe with greater wind speeds. In response to growing awareness of disasters that can result from climate change, the International Atomic Energy Agency (IAEA), released a safety guide in 2003 detailing flood-related hazards to nuclear power plants on coastal and river sites. The safety guide suggests that newly constructed plants should account for an increase in wind strength of between 5-10 percent over the 100 year life span of a nuclear plant due to the effect of climate change. This recommendation appears to be based more on the dire consequence of the failure of a nuclear plant rather than based on a statistical and proven model. Nonetheless it is deemed prudent to make allowance for a possible increase in wind strength.

2 Source: - Guidelines for Responding to the Effects of Climate Change in Coastal and Ocean Engineering, June 2013 (Reference 12)

Ref (16) IPCC (2013) 0.82 m in 2100





The upper bound recommendations from the IAEA have been adopted for this project, namely a 10% increase in wind strength over a 100 year life span. The design life of this project is 50 years therefore a 5% increase in wind strength has been allowed for in this project over and above the residual 1:50 year wind speed.

2.4 Storm Surge

Storm surge is an abnormal rise of water generated by a storm, over and above the predicted astronomical tides. Storm surge is produced by water being pushed toward the shore by the force of the winds moving cyclonically around the storm (wind set up) together with the low barometric pressure associated with intense storms causing a rise in sea water level. The US National Weather Service, who have records of extreme storm surge events, state that the wind setup component is the primary component accounting for 95% of the total storm surge with the low pressure component accounting for only 5% of the storm surge. Both the wind setup component and the low pressure component are a factor of the wind speed. The wind setup is proportional to the square of the wind speed i.e. (wind speed)2, whilst the low pressure component is directly proportional to the wind speed.


As stipulated in section 2.1 above, the design approach has been to first determine a current residual value for storm surge based on a statistical analysis of historic data, and then increase this value to account for climate change. PRDW, 2003, analysed the tide records for the Port of Durban for the period 1972 to 2001 and compared these with astronomical tide predictions, the difference between the two giving the storm surge value. A statistical analysis on these results revealed an increase in tide level of 0.69m for a 1:100 year storm surge event. Although the project design life is 50 years, the 1:50 year event value is not available and we have therefore conservatively adopted the 0.69m value as the residual value for storm surge. To calculate the effect of climate change ZAA have used the 5% increase in wind speed as explained in section 2.3.2 above and applied this percentage to the components affecting storm surge.

Increase in storm surge = (1.05)2 * 0.95 (Wind setup) + 1.05 * 0.05 (Low pressure) = 1.1

Therefore a 10% increase is applied to the residual storm setup value.

i.e. Design criteria storm setup value = 0.69 x 1.1 = 0.759 m

2.5 Other parameters

While the primary climate change vulnerability risks to the proposed project relate to sea level rise, coastal storm surge and wind phenomena, there are other aspects of climate change that may result in lesser risks to the proposed project.

2.5.1 Temperature

Future downscaled projections for changes in temperature are available for the Durban region. According to the Durban 2010/2011 Municipal Climate Protection Programme report (Ref 17), downscaled projections “suggest that an increase of 1.5-2.5 °C in mean annual temperature by 2045-2065”. The projections are summary values produced by the University of KwaZulu-Natal and presumably informed by the IPCC AR4 GCM data.

http://tidesandcurrents.noaa.gov/




2.5.2 Rainfall

Short duration design rainfalls and their relative intensity (mm/hr) are relevant to the design of the storm water management system for the project. The frequency of these storms is of less relevance to the design of the storm water management system. Limited information is available on the predicted increase in rainfall intensity in the Durban area. Statistically downscaled data for precipitation is generally regarded as less reliable than that for temperature. The Durban 2010/2011 Municipal Climate Protection Programme report that “Rainfall is likely to increase slightly overall, but this rainfall will fall over shorter time periods, which means that streamflows will be higher and faster”. The recently released “Durban Climate Change Strategy - Water Theme Report: Draft for Public Comment, January 2014” (Ref 18) recommends increasing designs by 10% or even more as a precaution against increased extreme events under future climatic conditions.

2.5.3 Ocean Acidification

Ocean acidification is the term given to the decrease in the pH of the Earth's oceans, caused by the uptake of anthropogenic carbon dioxide (CO2) from the atmosphere. As CO2 dissolves into the oceans, rivers and lakes, some of it reacts with the water to form carbonic acid. The potential impact of this acidification on the concrete quay wall has been examined.




3.0 IMPACTS ON DESIGN

3.1 Selection of cope level taking into account sea level rise and storm surge

In order to mitigate all known conditions and prevent overtopping of the new quays during their operational life, the selection of the cope height must take into account all relevant factors including those affected by climate change.

The primary principle is that the new quays must not be vulnerable to overtopping, breaking waves or excessive spray that would compromise their utilisation. Further, their vulnerability must not be compromised in the unlikely event that all of the factors affecting water level occur concurrently.

3.1.1 Predicted Water Levels to 2069

The water level in the Port of Durban is influenced by the following factors which are divided into divided into two groups:

• Factors affected by climate change ─ Sea level rise due to climate change ─ Storm surges including barometric pressure and wind set up

• Factors unrelated to climate change

─ Astronomical tides ─ Short period waves due to ship’s wake effects

The values to be used for the factors affected by climate change are as detailed in section 2.2 and 2.4 above. The Astronomical Tide Predictions as defined by the SA Navy Hydrographer and Chart SAN 2013 are as follows TABLE 3.1 : TIDAL RANGE

Tide Abbreviation Level m, Chart Datum Port * Highest Astronomical Tide HAT 2.287 Mean High Water Springs MHWS 1.997 Mean Level ML 1.097 Mean Low Water Springs MLWS 0.197 Lowest Astronomical Tide LAT -0.013

* Note that Chart Datum is defined by the SA Navy Hydrographer as 0.913 m below the Land Levelling Datum, but it is defined by TNPA as 0.900 m below this level. The reference level referred to will be Chart Datum Port, (CDP).

Short period waves due to the ship's wake effects will be superimposed on the still water level and a maximum wave height of 0.6 m (amplitude = 0.3 m) has been allowed for within the port.

Therefore a maximum water level is calculated as follows:

TABLE 3.2: WATER LEVELS Factor affecting Water Level 2069 Value 2100 Value Base line – LAT = Chart Datum 0.000 0.000 Tidal Range to HAT 2.287 2.287 Storm Surge 0.759 0.828 Wave allowance 0.300 0.300 Sea Level Rise during Design Life 0.580 0.82 Water level 3.926 4.235 Cope Level 4.25 4.25 Free board 0.324 0.015

A cope level of +4.25m CDP has been used in the design which allows for a freeboard of 0.324m.




3.1.2 Sensitivity Analysis – Predicted Water Levels at 2100

A sensitivity analysis has been undertaken investigating the probable water levels based on climate change increases using 2100 increase predictions. Using a SLR of 0.79m and a storm surge value of 0.828m (based on a 20% increase due to climate change), the maximum water level predicted is +4.205m CDP. The above scenarios of cope level vs. predicted water levels are graphically illustrated in Figure 4.1. Figure 4.1.1 shows the present situation, where the cope level is at +3.72m CDP. This figure shows that the current level allows for the full tidal range, waves and storm surge, as well as 443mm of freeboard. Figure 4.1.2 shows the new design with a cope level of +4.25mCDP with the tidal range, waves and predicted storm surge after completion of construction in the year 2019. The freeboard at that time relative to the latter parameters is 973mm. Figure 4.1.3 shows how the new design with the cope level at +4.25m CDP deals with the tidal range, waves, the predicted storm surge and sea level rise at the end of the design life in the year 2069. At that time the freeboard will be approximately 324mm. Figure 4.1.4 shows the situation in the year 2100, 31 years after the end of the design life. The extreme water level at that time is due to sea level rise, tidal range, waves and storm surge and the freeboard will be approximately 15mm.

3.2 Structural design of new quay walls and quay furniture

A 5% increase in wind strength has been allowed for in this project over and above the residual 1:50 year wind speed for assessing the forces on vessels and structures. This has been taken into account in the design of the bollards, fenders and the quay structure (caisson and capping beam). The potential increase in maximum temperature has been accounted for when assessing temperature induced stresses and strains in the quay wall structure. The caisson structure is not overly sensitive to temperature induced stresses and therefore the increase in potential temperature has a negligible effect on the design.

3.3 Storm water system

The storm water system has been designed with additional capacity to cope with flows from storms with potential increased rainfall intensity. The capacity of the system has been checked and is in excess of the capacity required for a 10% increase in rainfall intensity as recommended in “Durban Climate Change Strategy - Water Theme Report: Draft for Public Comment, January 2014” (Ref 18).

3.4 Concrete design for durability

It is highly unlikely that ocean acidification will occur to such an extent that it affects the durability of the concrete in the quay walls. Nonetheless, the potential effect has been examined. A detailed concrete specification for the project has been compiled to ensure durability of the concrete in a marine environment. Concrete in a marine environment is subject to chloride ingress (salts from the sea water) which can cause severe reinforcement corrosion and deterioration of concrete. Special measures which combat chloride ingress (increased concrete strengths, decreased permeability, the use of cement extenders etc.) have been specified to reduce potential deterioration and maintenance issues in marine concrete to acceptable levels. Although not normally associated with concrete in a marine environment, carbonation and acid attack are other forms of chemical attack that can cause deterioration in concrete. The measures to combat these forms of attack are the same as those used to combat chloride ingress (increased concrete strengths, decreased permeability, the use of cement extenders etc.) and thus the specification for concrete in marine environment contains the required measures to combat the highly unlikely attack from ocean acidification.




Fig. 4.1.1 Existing Quaywall

Fig. 4.1.2 Post Construction – Year 2019

Fig. 4.1.3 End of Structure Design Life – Year 2069

Fig. 4.1.4 Post Structure Design Life – Year 2100

Figure 4.1: Cope Levels vs. Predicted Water Levels




4.0 IMPACT DURING CONSTRUCTION PHASE

At all times during construction of the new quays, which is estimated to take approximately 5 years, i.e. to about 2019, the old quays will remain in place and the new quays will be built in front of them and to a level some 14% higher. The cope height of the existing quays at Pier 2 is at +3.72 m CDP. This has proved to be entirely adequate for storm, wave and tidal conditions since their construction some 60 years ago and it is predicted that they will remain adequate during the construction life of the project. Where there are currently no existing quays or in some small areas where the top of the existing quays will be demolished, Pier 2 and its inland structures will be protected by sheet piles while the new quays are constructed. There is thus no vulnerability or risk of flooding during the construction period.

5.0 MITIGATION OF RISKS IN CONSTRUCTION AND OPERATIONAL PHASES

Particular attention has been paid in the engineering design to identify and mitigate the risks associated with climate change effects during both the construction and operational phases of the proposed facilities at Pier 2. Risk mitigation with respect climate change is summarised in Table 5.1

6.0 CONCLUSION

This report has reviewed and summarised available literature on parameters affected by climate change that are relevant to the marine engineering design for this project. The IPCC, (2013) Climate Change 2013, Ref (16), has been adopted as the primary reference for this report. This is in agreement with IPCC AR4 (2007), together with the scaled up ice sheet discharge allowance, projected from 2095 to 2100. This has been supplemented by guidelines produced by UK Climate Projections Report June 2009 (UKCP09) and the National Committee on Coastal and Ocean Engineering, Engineers Australia. A Bibliography is contained in the Annexure. This report clearly demonstrates that the chosen cope level of +4.25m CDP is sufficient, providing a freeboard of 0.324m over and above the allowed for accumulation of various upper bound increases for climate change affected parameters. This indicates clearly that the risks and vulnerability of the new quays to climate change, and in particular sea level rise and storm surge, have been minimised and that the selected cope height of 4.25 m originally proposed by Transnet for this project is safe, conservative for its design life of 50 years from the projected completion date of 2019 and that a safe freeboard will still exist. In fact, given the year 2100 projection values, the structure is likely to be safe for a further 32 years after 2069. In all cases this is in the event of the simultaneous occurrence of all factors affecting the water level in the Port. Various improbable extreme scenarios (e.g. UKCP09 H++) have been taken into account when evaluating the design in terms of contingency planning in the event of these extreme scenarios. Other climate change affected parameters such as wind, rainfall and ocean acidification have been taken account during the design of the quay structures, storm water system and concrete specification. The threat of flooding during the construction phase has been evaluated and we conclude that construction will not adversely affect the current levels or increase the risk or vulnerability to flooding.




TABLE 5.1 RISK MITIGATION

Consequence LikelyhoodImpact

(Pre-Mitigation)MITIGATION BY BUILDING NEW QUAY COPE

LEVEL TO 4.25 M CDPLikelyhood

Impact (Post-Mitigation)

1Damage due to Long Term Sea

Level RiseOvertopping of Cope due to High

Tides, Storm Surge, Waves and SLR

Likely to occur, but not before year 2053 (ie when

the new quay is 34 years old)Major

Make sufficient allowance in design cope level of +4.25 m CDP to prevent this so that structure is safe to end of Design Life in 2069 and beyond to

2100

Rare Minor

2SLR exceeds design values due to

extreme ice sheet loss (eg UKCP09 H++ scenario)

Overtopping of Cope due to High Tides, Storm Surge, Waves and SLR

Likely to occur, but not before year 2043 (ie when

the new quay is 24 years old)Major

The design has included a freeboard allowance which will keep the cope safe against

overtopping until the year 2069 at the end of the design life, even if this most extreme event

occurs. If the decision is then made to extend the life of the structure beyond 2069, then the

current design allows for adaption of the cope to a higher level. It is noted that there will be

continual monitoring of the sea level during the operational life.

Rare Minor

3Inclement Weather - Rainfall much higher than expected

during construction

Delays in Project Schedule during construction Phase

Unlikely ModerateProvide for schedule delays in Project

programme. Unlikely Minor

4 Cyclone direct hit on DurbanHigh winds, heavy rainfall storm

surge, waves, currentsRare Moderate Rare Moderate

5 High wave conditions in Port Unlikely Minor Unlikely Minor

6 Storm surge Likely Minor Likely Minor

7 High swell conditions at seaDelay in dredging schedule during

constructionAlmost certain Minor

Allow for schedule delays in construction programme. Obtain regular weather reports and

plan accordingly.Almost certain Minor

8Damage to dredging work due to

weather and sea conditionsLarge amounts of sand deposited in dredged basins and channels

Unlikely Moderate Maintenance dredging to clear damaged areas Unlikely Minor

9

Damage to Central Sand Bank Extension due to inclement

weather, wind, waves, currents and storm surge

Extension slips into dredged basin Unlikely Moderate

Dredge material out of basin and repair damaged area. Central Sand Bank and Little Lagoon area

protected by sheetpile wall during construction and by caissons after construction.

Rare Minor

CLIMATE CHANGE RISK ASSESSMENT DURING CONSTRUCTION AND OPERATION TO END OF DESIGN LIFE IN YEAR 2069 AND BEYOND TO YEAR 2100

Higher than usual waves in Port combined with storm surge leads

to higher water levels

Existing quay has cope level at +3.72 m CDP which will be adequate during construction

phase. New cope level at +4.25 m CDP has been designed to cope with this to Year 2069 at end of

design life and beyoind to 2100. Normal maintenance to repair any damage to dredged

areas

WITHOUT MITIGATION ASSUMING NEW QUAY COPE LEVEL IS BUILT AT AT PRESENT QUAY COPE LEVEL OF 3.72 M CDP

MITIGATION BY BUILDING NEW QUAY COPE LEVEL TO 4.25 M CDP

IDENTIFIED RISKRISK

NUMBER



ZAA 1370 | RPT | 028 Rev F

7.0 REFERENCES

1 CSIR – Analysis of potential coastal zone climate change impacts and possible response options in the southern African Region – A Theron, M Rossouw

2 Water: ISSN 2073-4441 – 2012 – A perspective on Sea Level Rise and Coastal Storm Surge from Southern and Eastern Africa ; A case study near Durban, South Africa; Andrew A.Mather, Derek D. Stretch

3 Transnet – Sustainability Planning – Section 7 - Executive Overview of the 2012 edition of Transnet’s Long-term Planning Framework (LTPF)

4 Linear and nonlinear sea-level changes at Durban South Africa –South African Journal of Science 103 – November / December 2007 - A Mather

5 Rahmstorf S, Cazenave A, Church JA, Hansen JE, Keeling RF, Parker DE, Somerville RCJ (2007). Recent Climate Observations Compared to Projections. SCIENCE VOL 316,4 MAY 2007 p709. www.sciencemag.org Published online 1 February 2007; 10.1126/science.1136843

6 Bentley CR (1997). Rapid sea-level rise soon from West Antarctic Ice Sheet collapse? Science (Washington). Vol. 275, no. 5303, pp. 1077-1079.

7 Church JA and White NJ (2006). A 20th century acceleration in global Sea Level Rise, Geophys. Res. Lett., 33, L01602

8 IPCC (2007). Climate Change 2007: The Physical Science Basis, Summary for Policymakers. Contribution of Working Group I, II and III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, 104 pp, Geneva

9 Mather AA (2008). Sea Level Rise for the East Coast of Southern Africa. COPEDEC VII, 2008, Paper No: M-04; Dubai, UAE. 11 p

10 IPCC, 2012: Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation. A Special Report of Working Groups I and II of the Intergovernmental Panel on Climate Change [Field, C.B.,V. Barros, T.F. Stocker, D. Qin, D.J. Dokken, K.L. Ebi, M.D. Mastrandrea, K.J. Mach, G.-K. Plattner, S.K. Allen, M. Tignor, and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, UK, and New York, NY, USA, 582 pp.

11 Transnet Limited – Port of Durban – Pre-feasibility Report for the Proposed Berth Deepening of Berths 203 – 205 at DCT – PRDW, September 2011

12 The National Committee on Coastal and Ocean Engineering, Engineers Australia: Guidelines for responding to the effects of climate change in coastal and ocean engineering

13 WSP - Pre-Feasibility (FELl-2) Study for the Development of a Container Terminal at Pier 1, Phase 2, Port of Durban – October 2012.

14 Lowe, J. A., Howard, T. P., Pardaens, A., Tinker, J., Holt, J., Wakelin, S., Milne, G., Leake, J., Wolf, J., Horsburgh, K., Reeder, T., Jenkins, G., Ridley, J., Dye, S. and Bradley, S. (2009). UK Climate Projections science report: Marine and coastal projections, Met Office Hadley Centre, Exeter, UK.

15 Horton, R., Herweijer, C. Rosenzweig, C. Liu, J. Gornitz V. and Ruane, A. C. 2008: Sea level rise projections for current generation CGCMs based on the semi-empirical method. Geophysical Research Letters, 35, L02715, doi:10.1029/ 2007GL032486.

16 IPCC (2013) Climate Change 2013, The Physical Science Basis, Summary for Policy Makers, Working Group 1, Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change.

17 Durban’s Municipal Climate Protection Programme: Climate Change Adaptation Planning for a Resilient City 2010/2011.

18 Durban Climate Change - Strategy Water Theme Report: Draft for Public Comment - Professor Roland Schulze, Nicci Diederichs Mander, Catherine Hughes, Dr. Andrew Mather

http://www.sciencemag.org/



ZAA 1370 | RPT | 028 Rev F

ANNEXURE ADDITIONAL REFERENCES



ZAA 1370 | RPT | 028 Rev F

ADDITIONAL REFERENCES The following additional References have been provided by Dr A.A. Mather on 26 June 2013. To this list we have added reference 31.

19 Robert J. Nicholls, Natasha Marinova, Jason A. Lowe, Sally Brown, Pier Vellinga, Diogo de Gusmão, Jochen Hinkel and Richard S. J. Tol, Sea-level rise and its possible impacts given a ‘beyond 4°C world' in the twenty-first century Phil. Trans. R. Soc. A 2011 369, 161-181 doi: 10.1098/rsta.2010.0291

20 Rahmstorf, S. 2007. A semi-empirical approach to projecting future sea level rise, Science, 315, 368-370. 21 Jevrejeva, S. 2008. Global sea levels set to rise above IPCC forecasts. Geographical, June 2008, 11. 22 Horton, R., Herweijer, C. Rosenzweig, C. Liu, J. Gornitz V. and Ruane, A. C. 2008: Sea level rise projections

for current generation CGCMs based on the semi-empirical method. Geophysical Research Letters, 35, L02715, doi:10.1029/ 2007GL032486.

23 Siddall,M., Stocker, T.F.and Clark, P.U. 2009. Kinematic constraints on future sea level from past sea level change, Nature Geoscience, doi: 10.1038/NGE0587.

24 Pfeffer W. T., Harper, J. T. and O ’Neel S. 2008. Kinematic Constraints on Glacier Contributions to 21st-Century Sea-Level Rise, Science, 321, no. 5894, 1340-1343.

25 Global sea level linked to global temperature Martin Vermeer, and Stefan Rahmstorf www.pnas.org_cgi_doi_10.1073_pnas.0907765106

26 Delta Commission report: Working together with water A living land builds for its future, Findings of the Deltacommissie 2008 | summary and conclusions

27 John A Church, Neil J White, John R Hunter and Kurt Lambeck BRIEFING: a post-IPCC AR4 update on sea level rise, Antarctic Climate & Ecosystems Cooperative Research Centre

28 David L. Roberts, Panagiotis Karkanas, Zenobia Jacobs, Curtis W. Marean, Richard G. Roberts. Melting ice sheets 400,000 yr ago raised sea level by 13 m: Past analogue for future trends Earth and Planetary Science Letters 357–358 (2012) 226–237.

29 M.M Linham C.H. Green R.J. Nicholls COSTS OF ADAPTATION TO THE EFFECTS OF CLIMATE CHANGE IN THE WORLD’S LARGE PORT CITIES AVOID – Avoiding dangerous climate change DECC: GA0215 / GASRF123 2009 – 2012

30 Nicholls, R. J., Hanson, S. Herweijer, C. Patmore, N. Hallegatte, S. Corfee-Morlot, J. Chˆateau, J. Muir-Wood, R. 2008. Ranking port cities with high exposure and vulnerability to climate extremes: exposure estimates. OECD Environment Working Papers, No. 1, OECD publishing, OECD. doi:10.1787/ 011766488208.

31 United Nations – 2013 – UN System’s work on Climate Change - consequences.

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