MINISTERU G ĦAR-RI śORSI U MINISTRY FOR RESOURCES GĦALL-AFFARIJIET RURALI AND RURAL AFFAIRS
Dipartiment G ħat-Tindif u Manutenzjoni Cleansing and Maintenance Department
Sezzjoni Marittima u Unit Marine Section għall-Kontroll ta’ l-Ilma tax-Xita and Storm Water Control Unit
Marsaxlokk Harbour
Project Description Statement
PA 4576/09
April 2011
Marine & Storm Water Unit Project House, Triq Francesco Buonamici, FLORIANA FRN 1700, MALTA TEL: +356 2299 7893; FAX: +356 2124 9521
Contents Page Checklist - Amendments No. Refer to PDS Guidelines in Annex I
1.0 Introduction b 1.1 Project Description 3 b, d April 2011 1.2 Scope of Works 5 b 1.3 Details of person wishing to carry out the development 6 a
2.0 The Site 2.1 Alternative locations & uses 7 e 2.2 Physical characteristics of the Site 7 f 2.3 Present & Surrounding Land uses 7 g April 2011 2.4 Services on site 9 i
3.0 The Works 3.1 Persons on site 10 j 3.2 Proposed Timing of works 10 c 3.3 Materials to be used & Waste produced 11 k 3.4 Machinery 11 k 3.5 Access & Parking arrangements 12 l
4.0 The Environment 4.1 Environmental Impacts & Mitigation 13 m Measures
5.0 Conclusion 14
Annex I – PDS Guidelines 15
Annex II - Marsaxlokk Secondary 17 Breakwaters Report
Marsaxlokk Breakwater - Project Description Statement 2 1.0 Introduction
This report is being compiled to form part of planning application PA 4576/09 to aid MEPA officials form a conversant assessment of the proposed development and determine if further studies are required.
1.1 Project Description
The proposed interventions are located in the Marsaxlokk Bay which is a natural port in the south of the island. For centuries this village has been functioning as a fishermen’s village. The interventions will be carried out in different parts of the said bay, vide figure 1 below.
Figure 1 – Site Plan showing Proposed Interventions
Marsaxlokk Breakwater - Project Description Statement 3 The proposed development can be divided into three distinct interventions. Mainly:
a. the repair works and extension to the existing breakwater at Delimara. The existing breakwater arm spans circa 150m. The new extension increases the breakwater by another 100m. Side slopes will be at a gradient of 1:2 and 1:2.5. Base width will be circa 40m.
Photo 1 – Existing Breakwater at Delimara
b. the formation of a breach in an existing arm protruding from the inner part of Marsaxlokk bay. Proposed breach will be 6m wide by 2m deep and circa 25m long.
Photo 2 – Existing arm
Marsaxlokk Breakwater - Project Description Statement 4 c. the construction of an arm at ‘Il-Ponta tal-Qrejten’. The arm will be circa 104m long by
circa 32m wide at the base with sides sloping at 1:2.5.
Photo3 – Il-Ponta tal-Qrejten
Studies have shown that the combination of these interventions will mitigate the current wave action effects in the Marsaxlokk bay and provide adequate protection to vessels berthed inside the bay.
1.2 Scope of Works - Secondary Breakwater Arm
The construction of a secondary breakwater arm was conceived to counter the reflections of waves from the loading and unloading berth of Delimara Power Station. The latter structure was inducing wave disturbance in the inner fishing boat basin and other moorings outside the same basin. The breakwater arm as built with rock armour on its slopes which could then stop the waves by dissipating their energy.
However, storms have successively damaged this breakwater. A considerable part of the rock armour was carried away from the sides of the structure which resulted in erosion of the main body and the bull nose of same breakwater arm.
Before embarking on repairs, it was decided to check the wave climate along the length of the breakwater arm so that the repairs and strengthening could be designed to suit conditions. Moreover, tests were to be conducted to find out the ideal length related to required performance.
The opportunity was also taken to test other optional layouts introducing breakwater arms in various locations for comparison of sheltered related performances.
The net results show that the breakwater arm at the Ponta tal-Qrejten is most effective on its own and formidable when considered together with the extension of the existent breakwater arm. A breach in
Marsaxlokk Breakwater - Project Description Statement 5 the fishing boat basin in the inner harbour would also help dissipate some of the residual waves in the basin.
1.3 Details of person wishing to carry out the development
The applicant for this development is Carmel Mifsud Borg on behalf of:
MRRA Project House, Triq Francesco Buonamici, Floriana.
Marsaxlokk Breakwater - Project Description Statement 6 2.0 The Site
2.1 Alternative locations & uses
Prior to the consolidation of the current proposal, different scenarios of possible solutions have been tested and studied. The different options and the relevant results were formulated into a report prepared by Colin Toms & Partners for the Ministry for Resources and Rural Affairs (MRRA). A copy of this report can be found in Annex II.
2.2 Physical characteristics of the Site
All three sites are located in the Marsaxlokk inlet. The inner part of which harbours the fishing village of Marsaxlokk.
This area is a basin surrounded by higher grounds to which rain water diverts. Apart form the fishing village most of the surrounding land is still undeveloped. One road provides access to practically all parts of the bay from Delimara to Tal-Qrejten area. Along this road ‘Triq is-Sajjieda’ there is one major quay, a berthing facility and also a number of slipways located at intervals along this same quay.
2.3 Present & Surrounding Land uses
Figures 2 and 3 below, provide a clear picture of the present and surrounding land uses in the concerned areas.
Currently there is also a pending application PA 2958/10 for the construction of a Cold Store Facility vide Figure 2. These Cold Stores need to be constructed in all designated ports as stipulated in Article 17 of the Mediterranean Regulation 1967/2006 that states that “Member States shall designate a place to be used for landing, transhipping or a place close to the shore (designated ports) where landing or transhipping operations of blue fin tuna are permitted”. This building will be one of four such Cold Stores located in Marsaxlokk, Mgarr Gozo, Marfa and the Grand Harbour respectively.
Marsaxlokk Breakwater - Project Description Statement 7 Proposed Cold Stores & Extension of Quay PA2985/10
Fisheries Corporation Hardstanding Farmhouses
Power Restaurant Station Hanger Water Polo Enemalta Pitch Training Beach Centre
Figure 2 – Present & Surrounding Land Uses – Intervention a & c
Commercial & Residential
Parking Playing Field Sheltered Restaurant Marina
Arm
Boulders Beach
Figure 3 – Present & Surrounding Land Uses – Intervention b
Marsaxlokk Breakwater - Project Description Statement 8 2.4 Services on site
Only visual inspections of the surrounding areas were carried out. No services were noticed on the break water structure at Delimara and tal-Qrejten.
In the inner part of the bay were the breach is being proposed a number of light poles are located to illuminate the area. But these are situated on the periphery of the quay and will not interfere directly with the creation of the said breach.
Marsaxlokk Breakwater - Project Description Statement 9 3.0 The Works
3.1 Persons on site
The three structures projected can be subdivided into two:
a) Breakwater arms construction Specialized teams of workers will be engaged during the various phases of construction. i. Dredging : 12 seaman workers & 5 workers on land (40 days) ii. Backfilling: 10 truck drivers & 5 workers on land (40 days) iii. Armour: 5 truck drivers & 9 workers on land (40 days) iv. Cope Beam: 15 workers (50 days)
b) Opening of breach i. Dredging: 5 seamen & 5 workers on land (30 days) ii: Lining: 12 workers (20 days)
3.2 Proposed Timing of works
May to October 2011 & 2012 Extension of existing breakwater arm by 100m as well as strengthening of the existing 100m
May to October 2013 New breakwater at Ponta tal-Qrejten 100m long May to October 2014
May to October 2015 Opening of breach in the Fishing Boat basin joining same with the marine body of water outside the same basin.
The sequence shown above aims first to consolidate the existing structure which if left in its present condition runs the risk of total demolition. The projected extension needs to be planned concurrently with the repairs of the existing length of the breakwater arm. This will avoid duplicating expenses on the bull nose formation.
The construction of the breakwater arm at the Ponta tal-Qrejten will give much needed shelter to the larger boats at the hard standing. These trawlers may temporarily berth at the Delimara secondary breakwater arm until the new breakwater arm is built.
The breach in the Fishing Boat Basin will enable the residual waves in the same basin to dissipate through this breach.
Marsaxlokk Breakwater - Project Description Statement 10 3.3 Materials to be used & Waste produced
Waste material generated throughout the construction phase of this project will be mainly composed of excavated bedrock and existing broken concrete elements which need to be removed. Said materials will be disposed to approved dumping sites as stipulated by the relevant waste management authority i.e. Wasteserv Malta Ltd. All necessary permits and actions will be taken.
3.4 Machinery
The machinery envisaged to be employed on site includes:
• Excavator crane • Barges • Trucks • Bulldozer • Loaders • Hopper barges • Crane
Marsaxlokk Breakwater - Project Description Statement 11 3.5 Access & Parking arrangements
Areas have been identified on site vide Figure 4 below where vehicles and machinery can be temporary stored during the duration of the works. On the same drawing, the routes taken by vehicles to reach the respective sites are shown.
Proposed Cold Stores & Extension of Quay PA2985/10
Figure 4 – Temporary Parking & Access Arrangement
Marsaxlokk Breakwater - Project Description Statement 12 4.0 The Environment
4.1 Environmental Impacts & Mitigation Measures
The table below shows the envisaged environmental impacts with the respective mitigation measures that will be implemented.
Effect Stage Mitigation Measure Noise During Construction Noise levels to be retained with the limits stipulated by MEPA. Dust During Construction Core and rock armour material used in construction of the breakwaters will be washed in the quarry. Furthermore a silt curtain will be used to eliminate the plume from forming into the surrounding sea.
Dredging of sand and silt within the footprint of the Breakwater arms will be carried out by a grab dredger directly into a hopper barge and transported out to offshore spoil ground. The sea-craft used will be checked for oil leaks and the hopper barge closing mechanism ensured to be effective and serviced on regular basis covered by the required mechanical and electrical certification. Loss of Marine Habitat During Construction Loss of habitat underneath the footprint of the breakwater and the new arm is unavoidable. Once the proposed interventions will be finalised the structures will provide extra crevices and holes in which marine habitats can thrive. The proposed construction can be considered as an artificial reef where species can prosper. Traffic Generation During Construction Traffic will increase slightly during construction when material is being brought on site. No increase in traffic is envisaged once construction works have been finalised.
It is not envisaged that the proposed interventions will leave negative effects on the surrounding areas once the construction works are finished.
Marsaxlokk Breakwater - Project Description Statement 13 5.0 Conclusion
Optimistically this Project Description Statement answers the relevant queries which arise in similar projects. The author of this report can be contacted for any further data which maybe required.
______Patrick Griscti Soler A& C.E Marine & Storm Water Unit Ministry for Resources & Rural Affairs, Floriana
Marsaxlokk Breakwater - Project Description Statement 14
Annex I
Project Description Statement Guidelines
Marsaxlokk Breakwater - Project Description Statement 15
Marsaxlokk Breakwater - Project Description Statement 16
Annex II
Marsaxlokk Secondary Breakwaters Report
Refer to enclosed CD
Marsaxlokk Breakwater - Project Description Statement 17
Colin Toms & Partners for Malta MRRA
Marsaxlokk Secondary Breakwaters
Date: February 2010
Project Ref: R/3865/1
Report No: R.1583
Marsaxlokk Secondary Breakwaters
Summary
A number of protective breakwaters are proposed in the vicinity of Il - Bajja ta’Marsaxlokk, on the Island of Malta, by the Maltese Ministry for Resources and Rural Affairs. Various combinations of these breakwaters have been tested using the Boussinesq Waves model from the Danish Hydraulic Institute to ascertain their effectiveness at protecting the bay. The breakwater combinations provide varying degrees of protection and have impacts, both positive and negative, for the area they are designed to protect and for the bay outside their intended zone of protective influence.
The main report outlines a set of recommendations for the further development of the designs.
Appendix A considers an additional design and its subsequent installation phases.
Appendix B is similar in that it considers the very first phase of the entire project which is the implementation of the dredged fairway.
Appendix C considers the behaviour of the first stage of the favoured design during a more frequent, ten occurrences annually, wave event.
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Contents Page
Summary ...... i
1. Introduction...... 1 1.1 Methodology...... 1
2. Results and Discussion ...... 3 2.1 Baseline...... 3 2.2 Test 1 ...... 3 2.3 Test 2 ...... 4 2.4 Test 3 ...... 4 2.5 Test 4 ...... 5 2.6 Test 5 ...... 5 2.7 Test 6 ...... 5 2.8 Test 7 ...... 6 2.9 Test 8 ...... 7 2.10 Test 9 ...... 7 2.11 Test 10 ...... 8
3. Conclusions...... 8
4. Recommendations...... 9
5. References ...... 10
Appendices
A. Breach Combinations: Tests 11 to 13 B. Pre-Dredge Scenarios C. Frequent Wave Events (10 in 1 year): Tests 14 and 15
Tables
1. Model test scenarios...... 1 2. Breakwater reflection coefficients...... 2
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Figures
1. Il - Bajja ta'Marsaxlokk and its location on the Island of Malta 2. Proposed Breakwater Options and the Location of the Fairway 3. Cross Section Designs for the Marsaxlokk Proposed Breakwater Options 4. Significant Wave Height (m): Baseline 5. Wave Induced Currents: Baseline 6. Significant Wave Height (m): Test 1 7. Overview of Difference in Significant Wave Height: Test 1 8. Difference in Significant Wave Height (m): Test 1 - Baseline 9. Wave Induced Currents: Test 1 10. Significant Wave Height (m): Test 2 11. Overview of Difference in Significant Wave Height: Test 2 12. Difference in Significant Wave Height (m): Test 2 - Baseline 13. Wave Induced Currents: Test 2 14. Significant Wave Height (m): Test 3 15. Overview of Difference in Significant Wave Height: Test 3 16. Difference in Significant Wave Height (m): Test 3 - Baseline 17. Wave Induced Currents: Test 3 18. Significant Wave Height (m): Test 4 19. Overview of Difference in Significant Wave Height: Test 4 20. Difference in Significant Wave Height (m): Test 4 - Baseline 21. Wave Induced Currents: Test 4 22. Significant Wave Height (m): Test 5 23. Overview of Difference in Significant Wave Height: Test 5 24. Difference in Significant Wave Height (m): Test 5 - Baseline 25. Wave Induced Currents: Test 5 26. Significant Wave Height (m): Test 6 27. Overview of Difference in Significant Wave Height: Test 6 28. Difference in Significant Wave Height (m): Test 6 - Baseline 29. Wave Induced Currents: Test 6 30. Significant Wave Height (m): Test 7 31. Overview of Difference in Significant Wave Height: Test 7 32. Difference in Significant Wave Height (m): Test 7 - Baseline 33. Wave Induced Currents: Test 7
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34. Significant Wave Height (m): Test 8 35. Overview of Difference in Significant Wave Height: Test 8 36. Difference in Significant Wave Height (m): Test 8 - Baseline 37. Wave Induced Currents: Test 8 38. Significant Wave Height (m): Test 9 39. Overview of Difference in Significant Wave Height: Test 9 40. Difference in Significant Wave Height (m): Test 9 - Baseline 41. Wave Induced Currents: Test 9 42. Significant Wave Height (m): Test 10 43. Overview of Difference in Significant Wave Height: Test 10 44. Difference in Significant Wave Height (m): Test 10 - Baseline 45. Wave Induced Currents: Test 10 46. Wave Rays in Il - Bajja ta'Marsaxlokk
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1. Introduction
Il - Bajja ta’Marsaxlokk is situated at the rear of a naturally formed embayment on the south eastern most tip of Malta (Figure 1). The bay takes its name from the local fishing village. A substantial breakwater is present at the very outer limit of the embayment and provides protection to Marsaxlokk Freeport which is situated on the opposite side of the bay from Marsaxlokk fishing village. The Maltese Ministry for Resources and Rural Affairs (MRRA) wish to develop Il - Bajja ta’Marsaxlokk further to provide more vessel berths that are protected than are currently available. The remains of a breakwater extend from the land on the eastern side of the approaches to the fishing village. This breakwater was damaged during a storm when the foundations were undermined causing it to collapse. A harbour has been created at the very rear of the bay to provide protected berthing. A fairway provides passage to vessels to the harbour. This fairway currently experiences in-filling by sand which is understood to originate from the shallows on the eastern side of the bay. Wave activity is understood to be the mechanism by which this in-filling occurs.
A total of eight breakwaters are proposed by the MRRA. Their plan alignments are shown in Figure 2 while their cross-section designs are shown in Figure 3. The fairway will be dredged to a width of 25m and a depth of 5.5m below chart datum. The alignment of the fairway is shown in Figure 2.
1.1 Methodology
A sophisticated numerical wave disturbance model has been used to assess the proposed breakwater options. This model is the Boussinesq Waves model by the Danish Hydraulic Institute (DHI).
A total of eleven model runs are presented which include the baseline and ten different combinations of the eight proposed breakwater options, identified in Table 1. The baseline test provides the condition to which all the scenario tests can be compared.
Table 1. Model test scenarios
Breakwater Option Test 1a 1b 1c 1d 2a 2b 3a 3b Baseline 1 2 3 4 5 6 7 8 9 10
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Following the design of the breakwater cross-sections the breakwaters are assigned reflection characteristics according to their slope design (Figure 3). The assignment of reflection coefficients are presented in Table 2 based on Thompson et al (1996).
Table 2. Breakwater reflection coefficients
Reflection Coefficient Breakwater Option Front Slope Rear Slope 1a 0.5 n/a 1b 0.5 n/a 1c 0.5 0.6 1d 0.4 0.6 2a 0.4 n/a 2b 0.5 0.6 3a 0.4 n/a 3b 0.4 n/a
Throughout the Marsaxlokk Bay and adjoining bays there is a mixture of both man-made and natural coastlines which will reflect waves to different degrees. The reflective characteristics are included in the model and follow the guidance of Thompson et al (1996). Sections of coastline that are highly reflective, such as quay walls are assigned the highest reflection coefficients possible that model stability will allow. Sections of coastline that are rocky in character are assigned a reflection coefficient 0.5. Regions that are more shallowly sloped are assigned reflection coefficients typical of natural beaches of around 0.2.
The existing damaged breakwater in the baseline test is assigned a high reflection coefficient equivalent to the adjacent section of quay-side at the power station.
Although tidal ranges are small around the Islands of Malta the maximum range can be up to around 0.7m in the Marsaxlokk region (Griscti-Solar, 2009 – pers. comm.). Consequently, all tests are undertaken with a water level of 0.7m above local chart datum.
Input wave conditions are defined by ABPmer (2007) for a 1 in 50 year return period storm event which has an offshore significant wave height of 5.3m approaching from 150degrees (approximately south-south-east), which reduces to around 2.3m at the existing damaged breakwater.
Results from the model tests include significant wave height patterns and wave-induced current patterns. No specific validation has been undertaken against observations of either wave heights or currents. However, the baseline wave results are corroborated against wave height predicted by ABPmer (2007) at the location of the damaged breakwater for a 1 in 50 year return period storm event. The ABPmer (2007) conditions are derived from a model validated against both the UK Met Office European waters model and local ship observations. This is deemed appropriate while the main purpose of this modelling study is to provide comparative results.
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2. Results and Discussion
2.1 Baseline
Baseline summary: The 25m wide and 5.5m deep fairway is included in the baseline model so that only differences due to the breakwaters are identified. . Figure 4 - significant wave height; . Figure 5 - wave induced current.
Wave heights penetrating the bay and becoming incident upon the existing damaged breakwater are in the order of 2.26m which is commensurate with the wave height predicted at this location in ABPmer (2007) of 2.26m.
Wave heights in the protected berthing are in the order of 0.4-0.8m.
Wave induced currents are indicated to reach up to 2m/s in the region south of the existing damaged breakwater while they are in the order 1.4-1.6m/s in Il - Bajja ta’Marsaxlokk. The pattern of circulation is determined by the action of wave shoaling and breaking. Outside Il - Bajja ta’Marsaxlokk there is strong wave breaking to the western side which causes a clockwise current that heads from that western side toward the existing damaged breakwater. Inside Il - Bajja ta’Marsaxlokk the strongest wave breaking is experienced over the shallows on the eastern side of the bay which drives an anti-clockwise current. This circulation is expected to drive the transport mechanism by which the existing fairway can be filled with sand.
2.2 Test 1
Test 1 summary: Breakwater option 2a is a 150m long reconstruction of the existing but damaged breakwater and is the only breakwater included in this test. . Figure 6 - significant wave height; . Figure 7 - overview of differences in significant wave height; . Figure 8 - differences in significant wave height in Il - Bajja ta’Marsaxlokk; . Figure 9 - wave induced current.
Wave heights in the shelter of the reconstructed breakwater are in the order of 0.8-1m which is around half of the existing condition. This is partly due to the lengthening of the structure.
Wave heights throughout the fairway are generally elevated by around 0.1m (and up to 0.15m) which is thought to be due to the change in direction of wave propagation due to the reconstructed breakwater and resulting reflections inside the bay behind and from the power station quay walls. This scenario is thought to be much like conditions as they once were when the breakwater was still functional. However, no anecdotal evidence has been brought to light that suggests the original breakwater was detrimental to the wave heights throughout the bay. Although, with the differences being only in the order of 0.1m for this 1 in 50 year return event it would be difficult for a land based observer to detect this relatively small change.
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Wave heights in the protected berthing are slightly elevated and are generally in the order of 0.6-0.8m.
Small and patchy changes in wave heights are experienced throughout the whole bay. These are not more than ±0.05-0.1m. It is apparent that the reconstructed 2a breakwater reflects waves incident upon it into the centre of the wider bay (and toward the Marsaxlokk Freeport). Assessing the direction of these reflections from 2a breakwater suggests that they may have already been reflected from the power station quay wall and would otherwise be heading generally into Il - Bajja ta’Marsaxlokk.
No significant changes to the directional pattern of circulation by wave induced current are observed. However, there is some reduction in magnitude of the current as it flows into the region of the fairway.
2.3 Test 2
Test 2 summary: Breakwater options 1a and 2a are combined in this test. . Figure 10 - significant wave height; . Figure 11 - overview of differences in significant wave height; . Figure 12 - differences in significant wave height in Il - Bajja ta’Marsaxlokk; . Figure 13 - wave induced current.
The addition of 1a breakwater modifies the pattern of wave reflection further throughout Il - Bajja ta’Marsaxlokk. A general increase in wave heights are experienced. This is thought to be a result of the difference in reflective properties of the existing coastline and the proposed rock armour of the 1a breakwater where the rock armour has higher reflective properties than the gradient of the existing natural shoreline.
Wave heights in the protected berthing area are elevated also.
Similarly, small and patchy changes in wave heights are experienced throughout the whole bay. These are not more than ±0.05-0.1m.
Once again, no significant changes to the directional pattern of circulation by wave induced current are observed. But there is further slight reduction of the magnitude of those currents in the fairway region making them around 0.15m/s lower than the baseline test.
2.4 Test 3
Test 3 summary: Breakwater options 1a, 1b and 2a are combined in this test. . Figure 14 - significant wave height; . Figure 15 - overview of differences in significant wave height; . Figure 16 - differences in significant wave height in Il - Bajja ta’Marsaxlokk; . Figure 17 - wave induced current.
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The addition of the 1b breakwater makes little further change to the wave heights throughout Il - Bajja ta’Marsaxlokk compared to Test 2. Similarly, wave induced currents show little additional modification.
Wave heights in the protected berthing area remain in the order of around 0.6-0.8m while wave heights in the fairway remain elevated by around 0.15m, although this is difficult to realise when the wave in this zone is around 1m.
2.5 Test 4
Test 4 summary: Breakwater options 1a, 1c and 2a are combined in this test. . Figure 18 - significant wave height; . Figure 19 - overview of differences in significant wave height; . Figure 20 - differences in significant wave height in Il - Bajja ta’Marsaxlokk; . Figure 21 - wave induced current.
Wave heights directly in the lee of 1c breakwater are reduced in height by around 0.05m but remain as high as 0.6m as do wave heights within the protected berthing area. No significant further changes to either the magnitudes or directions of wave induced currents are observed within Il - Bajja ta’Marsaxlokk.
2.6 Test 5
Test 5 summary: Breakwater options 1a, 1b, 1c and 2a are combined in this test. . Figure 22 - significant wave height; . Figure 23 - overview of differences in significant wave height; . Figure 24 - differences in significant wave height in Il - Bajja ta’Marsaxlokk; . Figure 25 - wave induced current.
Combining 1b and 1c breakwaters improves wave heights slightly directly along on the western quay wall in the approaches to the protected berthing. The wave height within the protected berthing area remains elevated by around 0.1m at approximately 0.6m
No significant further modification to the wave induced currents is apparent.
2.7 Test 6
Test 6 summary: Breakwater options 1a, 2a and 2b are combined in this test. . Figure 26 - significant wave height; . Figure 27 - overview of differences in significant wave height; . Figure 28 - differences in significant wave height in Il - Bajja ta’Marsaxlokk; . Figure 29 - wave induced current.
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Notable reductions in significant wave height can be observed in the lee of 2b breakwater. Wave heights here are in the order of 0.4-0.6m which is around 0.4m lower than the baseline test. Forward of 2b breakwater elevated wave heights are seen and are around 0.2m higher than baseline. Waves reflecting from the power station quayside toward the western shore of Il - Bajja ta’Marsaxlokk are ‘caught’ by 2b breakwater and prevented from further penetrating the bay. The shoreline to the south of 2b breakwater appears to be a mix of both rocky shore and beach. The beach type zones will dissipate wave energy incident upon them and therefore it may be beneficial to direct waves toward these areas to lower the overall wave climate.
The pattern and magnitude of wave induced currents is generally the same as the baseline test with the exception that 2b breakwater deflects the currents moving south along the western shore of Il - Bajja ta’Marsaxlokk back into the fairway. This may be to the benefit of the fairway by helping to move sediments toward either the south, and out of the bay, or to the shallows in the east from where the sediment may originate. However, this may be to the detriment of the breakwater foundations which will require scour protection to prevent undermining.
2.8 Test 7
Test 7 summary: Breakwater options 2a, 2b and 3a are combined in this test. . Figure 30 - significant wave height; . Figure 31 - overview of differences in significant wave height; . Figure 32 - differences in significant wave height in Il - Bajja ta’Marsaxlokk; . Figure 33 - wave induced current.
Reductions in significant wave height are observed throughout Il - Bajja ta’Marsaxlokk with addition of the extended existing breakwater (2a plus 3a) in combination with 2b breakwater. Wave heights in the lee of the 2a/3a breakwater are in the order of 0.6-0.8m, a reduction of around 0.4-0.6m. Similar reductions are observed directly in the lee of 2b breakwater. Wave heights throughout the remainder of Il - Bajja ta’Marsaxlokk are in the order of 0.4-0.8m which is an approximate overall reduction of 0.1m.
The 2a/3a breakwater reflects waves toward the Marsaxlokk Freeport on the opposite side of the bay. The effect of this is particularly apparent in the petrochemical berths in the lee of the Freeport breakwater where wave heights are elevated by around 0.1m.
The overall pattern of wave induced currents remains although the magnitude of the currents within Il - Bajja ta’Marsaxlokk are reduced compared to the baseline test by around 0.4m/s. This is to the benefit of the fairway in that it will reduce the infill by sediment.
However, wave induced currents are accelerated around the tip of the 3a breakwater. This occurs as the breakwater protrudes into the clockwise circulating current to the south and deflects some of the current into the lee of the breakwater. It will be necessary to protect the foundations of this breakwater from scour.
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2.9 Test 8
Test 8 summary: Breakwater options 2a, 3a and 3b are combined in this test. . Figure 34 - significant wave height; . Figure 35 - overview of differences in significant wave height; . Figure 36 - differences in significant wave height in Il - Bajja ta’Marsaxlokk; . Figure 37 - wave induced current.
Combining 2a/3a and 3b breakwaters provide reductions in wave height throughout Il - Bajja ta’Marsaxlokk. Directly in the lee of 2a/3a breakwater wave heights are reduced to around 0.4m, while the shelter of 3b yields waves of around 0.6m. Waves throughout Il - Bajja ta’Marsaxlokk are reduced by 0.2-0.4m to around 0.6-1.0m in height.
Wave heights in the protected berthing area at Marsaxlokk are very similar to those of the baseline test.
The reflections from the two breakwaters included in this test are directed towards the Marsaxlokk Freeport. Throughout the area of the Freeport wave heights are elevated by around 0.1m.
Wave induced current speeds inside Il - Bajja ta’Marsaxlokk are reduced to much lower than in the baseline test. In the baseline test current magnitudes are around 0.8-1.0m/s while in Test 8 they are reduced to around 0.4-0.6m/s. Some acceleration of current speed up to 0.8m/s passed the tip of the 3a breakwater is observed. Current speed is high along the face of 3b breakwater. Scour protection may well be required here.
2.10 Test 9
Test 9 summary: Breakwater options 1a, 2a and 3a are combined in this test. . Figure 38 - significant wave height; . Figure 39 - overview of differences in significant wave height; . Figure 40 - differences in significant wave height in Il - Bajja ta’Marsaxlokk; . Figure 41 - wave induced current.
Wave height directly in the lee of 2a/3a breakwater is reduced to less than 0.8m which is a 0.2m reduction over the baseline test. Reductions in the remainder of Il - Bajja ta’Marsaxlokk are limited as increases in wave height are observed widely of up to 0.2m. As per Tests 2-6, 1a breakwater acts to elevate wave height in Il - Bajja ta’Marsaxlokk by increasing in the reflectivity of the shoreline where it is placed.
Some modification of the general wave climate between the 2a/3a breakwater and the Marsaxlokk Freeport are apparent and are of the order ±0.05-0.1m. However, the petrochemical berths at the Freeport again experience a wave elevated by around 0.1m above the baseline test.
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Marsaxlokk Secondary Breakwaters
Wave induced currents in Il - Bajja ta’Marsaxlokk are reduced over a considerable area by the presence of 2a/3a breakwater to around 0.2-0.6m/s which is a notable improvement over the baseline test. The outer armour of this breakwater will be exposed to current speeds of notable magnitude and is expected to require scour protection to maintain its foundations.
2.11 Test 10
Test 10 summary: Breakwater options 1d and 2a are combined in this test. . Figure 42 - significant wave height; . Figure 43 - overview of differences in significant wave height; . Figure 44 - differences in significant wave height in Il - Bajja ta’Marsaxlokk; . Figure 45 - wave induced current.
This combination of breakwaters causes a general reduction in wave heights throughout Il - Bajja ta’Marsaxlokk in the order of 0.1-0.2m to generally below 0.6m. Wave height in the protected berths is maintained at 0.4-0.8m which is comparable to the baseline test.
The 1d and 2b breakwaters provide good shelter along the western quay side in the approaches to the protected berthing.
Wave heights forward of the 2b breakwater are elevated to around 2m, an increase of up to 0.4m compared the baseline test.
A band of elevated wave height can be observed extending southwards from the tip of the 2a breakwater. This is as increase of around 0.2m and is thought to be a result of modified wave reflection due to 1d breakwater.
Reflections from 2a breakwater again elevate wave heights in the petrochemical berths at the Marsaxlokk Freeport by around 0.1m.
Wave induced currents are low, around 0.1-0.6m/s, in the zone between the 1d and 2b breakwaters. The anti-clockwise circulation within Il - Bajja ta’Marsaxlokk still exists and is of a magnitude comparable to those in the baseline test. Critically however, the circulation is ‘squeezed’ between the tips of the 2a and 1d breakwaters and will reduce the transport of sediment from the shallows to the fairway, with only a southern portion of the fairway falling within the influence of this wave driven current. The magnitude of the wave induced current here suggests that these breakwaters will require scour protection to avoid undermining of their foundations.
Current magnitudes in the vicinity of 2b breakwater are around 0.1-0.2m/s.
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Marsaxlokk Secondary Breakwaters
3. Conclusions
From the series of tests it is possible to draw conclusions not only to the immediate performance of the breakwaters but to the mechanism by which waves reflect and refract within Il - Bajja ta’Marsaxlokk and ultimately arrive in the protected berthing area. Figure 46 shows wave rays for the approaching wave and an estimation of their paths.
Reflections from the power station quayside and the existing damaged breakwater are thought to head towards the Marsaxlokk Freeport. Lengthening this breakwater, either through repair or repair and extension, is expected to increase the quantity of reflected wave energy toward the Freeport to the detriment of the wave climate there.
4. Recommendations
It is recommended that further consideration is given to breakwater options and their careful alignment such that the wave that they reflect is directed to locations that can attenuate wave energy such as the coastline on the western side of Il - Bajja ta’Marsaxlokk opposite the existing damaged breakwater or the naturally shallow gradients of the northern boundary of the bay. This can be implemented in combination with artificial spending beaches placed in locations that are currently reflective, such as the shoreline to the north of the existing damaged breakwater, and carefully aligning breakwaters to direct reflected wave energy toward those spending beaches.
A note of caution must be applied to the use of attenuating structures near semi-enclosed harbours. The action of wave breaking causes the spreading of wave energy (period/wavelength) to different frequencies (longer and shorter period/wavelength). These new waves can interact problematically with the nearby harbours if the length of those waves is close to the resonant length of the harbour.
It is apparent that there are critical locations at which structures could be placed to optimise wave attenuation. Such a location is the region on Figure 46 where the yellow, red and orange wave rays intersect. A wave attenuating feature placed here could be greatly beneficial. For example, an artificial island with shoreline gradient characteristics similar to the existing natural coastline to the north east of this location may be advantageous, although it must be carefully shaped to maximise its effectiveness. Alternatively, an artificial reef here could be shaped to refract waves onto the existing shallow gradients of the north east shoreline.
Further advantage may be gained by a breakwater similar to 2b but modifying its alignment to reflect waves toward the opposite, eastern, coastline where the addition of a shallow gradient spending beach could attenuate the wave energy.
The yellow coloured wave rays of Figure 46, which indicate the path of waves propagating into the bay, could be re-directed by refracted toward the shore or spending beaches by using reef type structures in the region between breakwater options 2a, 2b and 3b. This option may recover the greatest area of safe berthing within Il - Bajja ta’Marsaxlokk.
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Marsaxlokk Secondary Breakwaters
The existing damaged breakwater is thought to reflect waves toward the Marsaxlokk Freeport. Instead of refurbishing this breakwater it may be beneficial to remove it and allow wave energy to dissipate over a shallow gradient spending beach placed along the shoreline.
5. References
ABPmer (2007). Extreme Wind and Wave Conditions for Malta. ABP Marine Environmental Research Ltd, Report No. R.1375, for Colin Toms & Partners
Thompson E.F., Chen H.S. & Hadley L.L.(1996). Validation of Numerical Model for Wind Waves and Swell in Harbours. ASCE Journal of Waterway, Port, Coastal, and Ocean Engineering, Vol. 122, No. 5, p245-257.
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Figures
South Quay
Il-Bajja ta’Marsaxlokk
Fishing Village Haven
Existing damaged breakwater Power station
Il - Bajja ta'Marsaxlokk and its location on the Island of Malta Figure 1 Proposed Breakwater Options and the Location of the Fairway Figure 2 Breakwater: 1D Breakwater: 1A, 1B
Breakwater: 2A, 3A, 3B
Breakwater: 2B, 1C
Cross Section Designs for the Marsaxlokk Proposed Breakwater Options Figure 3 4 3.5 Hs (m) A1 - A2 3 2.5 2 1.5 1 0.5 0 0 100 200 300 400 500 600chainage (m) 700 4 Hs (m) B1 - B2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) C1 - C2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) D1 - D2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) E1 - E2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) F1 - F2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) G1 - G2 3
2
1
0 0 100 200chainage (m) 300 Baseline Significant Wave Height
Significant Wave Height (m): Baseline Figure 4 2 Speed (m/s) A1 - A2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) B1 - B2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) C1 - C2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) D1 - D2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
1 Speed (m/s) 0.8 E1 - E2 0.6 0.4 0.2 0 0 100 200chainage (m) 300
0.2 Speed (m/s) F1 - F2 0.15
0.1
0.05
0 0 100 200chainage (m) 300
0.2 Speed (m/s) G1 - G2 0.15
0.1
0.05
0 0 100 200chainage (m) 300 Baseline Current Speed
Wave Induced Currents: Baseline Figure 5 4 Hs (m) A1 - A2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) B1 - B2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) C1 - C2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) D1 - D2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) E1 - E2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) F1 - F2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) G1 - G2 3
2
1
0 0 100 200chainage (m) 300 Baseline Significant Wave Height Scenario Significant Wave Height
Significant Wave Height (m): Test 1 Figure 6 Overview of Difference in Significant Wave Height: Test 1 Figure 7 1 Hs (m) A1 - A2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) B1 - B2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) C1 - C2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) D1 - D2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
0.5 Hs (m) E1 - E2 0.3
0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) F1 - F2 0.3
0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) G1 - G2 0.3
0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5 Difference in Significant Wave Height
Difference in Significant Wave Height (m): Figure 8 Test 1 - Baseline 2 Speed (m/s) A1 - A2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) B1 - B2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) C1 - C2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) D1 - D2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
1 Speed (m/s) 0.8 E1 - E2 0.6 0.4 0.2 0 0 100 200chainage (m) 300
0.2 Speed (m/s) F1 - F2 0.15
0.1
0.05
0 0 100 200chainage (m) 300
0.2 Speed (m/s) G1 - G2 0.15
0.1
0.05
0 0 100 200chainage (m) 300 Baseline Current Speed Scenario Current Speed
Wave Induced Currents: Test 1 Figure 9 4 Hs (m) A1 - A2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) B1 - B2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) C1 - C2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) D1 - D2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) E1 - E2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) F1 - F2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) G1 - G2 3
2
1
0 0 100 200chainage (m) 300 Baseline Significant Wave Height Scenario Significant Wave Height
Significant Wave Height (m): Test 2
Significant Wave Height (m): Test 2 Figure 10 Overview of Difference in Significant Wave Height: Test 2 Figure 11 1 Hs (m) A1 - A2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) B1 - B2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) C1 - C2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) D1 - D2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
0.5 Hs (m) E1 - E2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) F1 - F2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) G1 - G2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5 Difference in Significant Wave Height
Difference in Significant Wave Height (m): Figure 12 Test 2 - Baseline 2 Speed (m/s) A1 - A2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) B1 - B2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) C1 - C2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) D1 - D2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
1 Speed (m/s) 0.8 E1 - E2 0.6 0.4 0.2 0 0 100 200chainage (m) 300
0.2 Speed (m/s) F1 - F2 0.15
0.1
0.05
0 0 100 200chainage (m) 300
0.2 Speed (m/s) G1 - G2 0.15
0.1
0.05
0 0 100 200chainage (m) 300 Baseline Current Speed Scenario Current Speed
Wave Induced Currents: Test 2 Figure 13 4 Hs (m) A1 - A2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) B1 - B2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) C1 - C2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) D1 - D2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) E1 - E2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) F1 - F2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) G1 - G2 3
2
1
0 0 100 200chainage (m) 300 Baseline Significant Wave Height Scenario Significant Wave Height
Significant Wave Height (m): Test 3
Significant Wave Height (m): Test 3 Figure 14 Overview of Difference in Significant Wave Height: Test 3 Figure 15 1 Hs (m) A1 - A2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) B1 - B2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) C1 - C2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) D1 - D2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
0.5 Hs (m) E1 - E2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) F1 - F2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) G1 - G2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5 Difference in Significant Wave Height
Difference in Significant Wave Height (m): Figure 16 Test 3 - Baseline 2 Speed (m/s) A1 - A2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) B1 - B2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) C1 - C2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) D1 - D2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
1 Speed (m/s) 0.8 E1 - E2 0.6 0.4 0.2 0 0 100 200chainage (m) 300
0.2 Speed (m/s) F1 - F2 0.15
0.1
0.05
0 0 100 200chainage (m) 300
0.2 Speed (m/s) G1 - G2 0.15
0.1
0.05
0 0 100 200chainage (m) 300 Baseline Current Speed Scenario Current Speed
Wave Induced Currents: Test 3 Figure 17 4 Hs (m) A1 - A2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) B1 - B2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) C1 - C2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) D1 - D2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) E1 - E2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) F1 - F2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) G1 - G2 3
2
1
0 0 100 200chainage (m) 300 Baseline Significant Wave Height Scenario Significant Wave Height
Significant Wave Height (m): Test 4
Significant Wave Height (m): Test 4 Figure 18 Overview of Difference in Significant Wave Height: Test 4 Figure 19 1 Hs (m) A1 - A2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) B1 - B2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) C1 - C2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) D1 - D2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
0.5 Hs (m) E1 - E2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) F1 - F2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) G1 - G2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5 Difference in Significant Wave Height
Difference in Significant Wave Height (m): Figure 20 Test 4 - Baseline 2 Speed (m/s) A1 - A2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) B1 - B2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) C1 - C2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) D1 - D2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
1 Speed (m/s) 0.8 E1 - E2 0.6 0.4 0.2 0 0 100 200chainage (m) 300
0.2 Speed (m/s) F1 - F2 0.15
0.1
0.05
0 0 100 200chainage (m) 300
0.2 Speed (m/s) G1 - G2 0.15
0.1
0.05
0 0 100 200chainage (m) 300 Baseline Current Speed Scenario Current Speed
Wave Induced Currents: Test 4 Figure 21 4 Hs (m) A1 - A2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) B1 - B2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) C1 - C2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) D1 - D2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) E1 - E2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) F1 - F2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) G1 - G2 3
2
1
0 0 100 200chainage (m) 300 Baseline Significant Wave Height Scenario Significant Wave Height
Significant Wave Height (m): Test 5
Significant Wave Height (m): Test 5 Figure 22 Overview of Difference in Significant Wave Height: Test 5 Figure 23 1 Hs (m) A1 - A2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) B1 - B2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) C1 - C2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) D1 - D2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
0.5 Hs (m) E1 - E2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) F1 - F2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) G1 - G2 0.3
0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5 Difference in Significant Wave Height
Difference in Significant Wave Height (m): Figure 24 Test 5 - Baseline 2 Speed (m/s) A1 - A2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) B1 - B2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) C1 - C2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) D1 - D2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
1 Speed (m/s) 0.8 E1 - E2 0.6 0.4 0.2 0 0 100 200chainage (m) 300
0.2 Speed (m/s) F1 - F2 0.15
0.1
0.05
0 0 100 200chainage (m) 300
0.2 Speed (m/s) G1 - G2 0.15
0.1
0.05
0 0 100 200chainage (m) 300 Baseline Current Speed Scenario Current Speed
Wave Induced Currents: Test 5 Figure 25 4 Hs (m) A1 - A2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) B1 - B2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) C1 - C2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) D1 - D2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) E1 - E2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) F1 - F2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) G1 - G2 3
2
1
0 0 100 200chainage (m) 300 Baseline Significant Wave Height Scenario Significant Wave Height
Significant Wave Height (m): Test 6
Significant Wave Height (m): Test 6 Figure 26 Overview of Difference in Significant Wave Height: Test 6 Figure 27 1 Hs (m) A1 - A2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) B1 - B2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) C1 - C2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) D1 - D2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
0.5 Hs (m) E1 - E2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) F1 - F2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) G1 - G2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5 Difference in Significant Wave Height
Difference in Significant Wave Height (m): Figure 28 Test 6 - Baseline 2 Speed (m/s) A1 - A2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) B1 - B2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) C1 - C2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) D1 - D2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
1 Speed (m/s) 0.8 E1 - E2 0.6 0.4 0.2 0 0 100 200chainage (m) 300
0.2 Speed (m/s) F1 - F2 0.15
0.1
0.05
0 0 100 200chainage (m) 300
0.2 Speed (m/s) G1 - G2 0.15
0.1
0.05
0 0 100 200chainage (m) 300 Baseline Current Speed Scenario Current Speed
Wave Induced Currents: Test 6 Figure 29 4 Hs (m) A1 - A2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) B1 - B2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) C1 - C2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) D1 - D2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) E1 - E2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) F1 - F2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) G1 - G2 3
2
1
0 0 100 200chainage (m) 300 Baseline Significant Wave Height Scenario Significant Wave Height
Significant Wave Height (m): Test 7
Significant Wave Height (m): Test 7 Figure 30 Overview of Difference in Significant Wave Height: Test 7 Figure 31 1 Hs (m) A1 - A2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) B1 - B2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) C1 - C2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) D1 - D2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
0.5 Hs (m) E1 - E2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) F1 - F2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) G1 - G2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5 Difference in Significant Wave Height
Difference in Significant Wave Height (m): Figure 32 Test 7 - Baseline 2 Speed (m/s) A1 - A2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) B1 - B2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) C1 - C2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) D1 - D2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
1 Speed (m/s) 0.8 E1 - E2 0.6 0.4 0.2 0 0 100 200chainage (m) 300
0.2 Speed (m/s) F1 - F2 0.15
0.1
0.05
0 0 100 200chainage (m) 300
0.2 Speed (m/s) G1 - G2 0.15
0.1
0.05
0 0 100 200chainage (m) 300 Baseline Current Speed Scenario Current Speed
Wave Induced Currents: Test 7 Figure 33 4 Hs (m) A1 - A2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) B1 - B2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) C1 - C2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) D1 - D2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) E1 - E2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) F1 - F2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) G1 - G2 3
2
1
0 0 100 200chainage (m) 300 Baseline Significant Wave Height Scenario Significant Wave Height
Significant Wave Height (m): Test 8
Significant Wave Height (m): Test 8 Figure 34 Overview of Difference in Significant Wave Height: Test 8 Figure 35 1 Hs (m) A1 - A2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) B1 - B2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) C1 - C2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) D1 - D2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
0.5 Hs (m) E1 - E2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) F1 - F2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) G1 - G2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5 Difference in Significant Wave Height
Difference in Significant Wave Height (m): Figure 36 Test 8 - Baseline 2 Speed (m/s) A1 - A2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) B1 - B2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) C1 - C2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) D1 - D2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
1 Speed (m/s) 0.8 E1 - E2 0.6 0.4 0.2 0 0 100 200chainage (m) 300
0.2 Speed (m/s) F1 - F2 0.15
0.1
0.05
0 0 100 200chainage (m) 300
0.2 Speed (m/s) G1 - G2 0.15
0.1
0.05
0 0 100 200chainage (m) 300 Baseline Current Speed Scenario Current Speed
Wave Induced Currents: Test 8 Figure 37 4 Hs (m) A1 - A2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) B1 - B2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) C1 - C2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) D1 - D2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) E1 - E2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) F1 - F2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) G1 - G2 3
2
1
0 0 100 200chainage (m) 300 Baseline Significant Wave Height Scenario Significant Wave Height
Significant Wave Height (m): Test 9
Significant Wave Height (m): Test 9 Figure 38 Overview of Difference in Significant Wave Height: Test 9 Figure 39 1 Hs (m) A1 - A2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) B1 - B2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) C1 - C2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) D1 - D2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
0.5 Hs (m) E1 - E2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) F1 - F2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) G1 - G2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5 Difference in Significant Wave Height
Difference in Significant Wave Height (m): Figure 40 Test 9 - Baseline 2 Speed (m/s) A1 - A2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) B1 - B2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) C1 - C2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) D1 - D2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
1 Speed (m/s) 0.8 E1 - E2 0.6 0.4 0.2 0 0 100 200chainage (m) 300
0.2 Speed (m/s) F1 - F2 0.15
0.1
0.05
0 0 100 200chainage (m) 300
0.2 Speed (m/s) G1 - G2 0.15
0.1
0.05
0 0 100 200chainage (m) 300 Baseline Current Speed Scenario Current Speed
Wave Induced Currents: Test 9 Figure 41 4 Hs (m) A1 - A2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) B1 - B2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) C1 - C2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) D1 - D2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) E1 - E2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) F1 - F2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) G1 - G2 3
2
1
0 0 100 200chainage (m) 300 Baseline Significant Wave Height Scenario Significant Wave Height
Significant Wave Height (m): Test 10 Figure 42 Overview of Difference in Significant Wave Height: Test 10 Figure 43 1 Hs (m) A1 - A2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) B1 - B2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) C1 - C2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) D1 - D2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
0.5 Hs (m) E1 - E2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) F1 - F2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) G1 - G2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5 Difference in Significant Wave Height
Difference in Significant Wave Height (m): Figure 44 Test 10 - Baseline 2 Speed (m/s) A1 - A2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) B1 - B2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) C1 - C2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) D1 - D2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
1 Speed (m/s) 0.8 E1 - E2 0.6 0.4 0.2 0 0 100 200chainage (m) 300
0.2 Speed (m/s) F1 - F2 0.15
0.1
0.05
0 0 100 200chainage (m) 300
0.2 Speed (m/s) G1 - G2 0.15
0.1
0.05
0 0 100 200chainage (m) 300 Baseline Current Speed Scenario Current Speed
Wave Induced Currents: Test 10 Figure 45 Wave Rays in Il - Bajja ta'Marsaxlokk Figure 46
Appendices
Appendix A
Breach Combinations: Tests 11 to 13
Marsaxlokk Secondary Breakwaters
Appendix A. Breach Combinations: Tests 11 to 13
Three additional tests demonstrate the combined performance of the preferred breakwater options in combination with a breach through the south quay of the inner harbour. In these tests the breach is implemented as a passage through which water can flow but through which waves cannot pass. This is so that the passage can enable flushing by wave induced currents without detriment to the wave climate inside the inner harbour. To implement this in the model ‘wave filter’ parameters are adjusted, this attenuates waves but does not affect wave induced current flow. This approach simulates a permeable wave attenuating structure.
Table A1. Model test scenarios: Tests 11 to 13
Breakwater Option Test 1a 1b 1c 1d 2a 2b 3a 3b Breach 11 12 13
Test 11
Test 11 summary: Breakwater options 2a and 2b are combined in this test along with a breach through the south quay. . Figure A.1 - significant wave height; . Figure A.2 - overview of differences in significant wave height; . Figure A.3 - differences in significant wave height in Il - Bajja ta’Marsaxlokk; . Figure A.4 - wave induced current.
A combination of 2a and 2b breakwaters give a favourable reduction in wave height throughout Il - Bajja ta’Marsaxlokk. There is some elevation in wave height in the centre of the bay directly between the two breakwaters. This is due to the refraction of waves out of the fairway channel and onto the shallows in that location.
Wave induced current circulation patterns are largely unaffected. Some flow is experienced through the breach into the fishing village haven. This is localised and is not apparent throughout the entire haven.
Test 12
Test 12 summary: Breakwater options 1d, 2a and 2b are combined in this test along with a breach through the south quay. . Figure A.5 - significant wave height; . Figure A.6 - overview of differences in significant wave height; . Figure A.7 - differences in significant wave height in Il - Bajja ta’Marsaxlokk; . Figure A.8 - wave induced current.
R/3865/1 A.1 R.1583
Marsaxlokk Secondary Breakwaters
The addition of the 1d breakwater further reduces wave height. Significantly, the 1d breakwater prevents waves that are reflected from the coastline north of the 2a breakwater penetrating the main berthing areas of the bay. Wave heights adjacent to the 2b breakwater are elevated over Test 11.
Breakwater 1d deflects the anticlockwise current circulation to the south. The mechanism by which sediments can be transported from the shallows in the eastern side of the bay and into the fairway is disrupted. The fairway channel outside the protection of those breakwaters will still be subject to infilling by the sediments by that mechanism. A weaker current flow is observed in the lee of 1d and 2b breakwaters
Similar magnitude flows are experienced through the breach as for Test 11.
Test 13
Test 13 summary: Breakwater options 1d, 2a, 2b and 3a are combined in this test along with a breach through the south quay. . Figure A.9 - significant wave height; . Figure A.10 - overview of differences in significant wave height; . Figure A.11 - differences in significant wave height in Il - Bajja ta’Marsaxlokk; . Figure A.12 - wave induced current.
The addition of 3a breakwater improves the wave climate in the lee of the 2a/3a breakwater.
The anti clockwise circulation between 1d and 3a breakwaters is reduced in overall magnitude which will likely lessen the transport of sediment from the shallow areas to the eastern side of the bay into the fairway. Notably, with the reduction in magnitude of this current circulation the currents circulating in the lee of the 1d and 2b breakwaters now flow out from between those breakwaters. This gives rise to a mechanism which will potentially transport sediment along the fairway and out of the haven.
R/3865/1 A.2 R.1583
4 Hs (m) A1 - A2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) B1 - B2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) C1 - C2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) D1 - D2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) E1 - E2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) F1 - F2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) G1 - G2 3
2
1
0 0 100 200chainage (m) 300 Baseline Significant Wave Height Scenario Significant Wave Height
Significant Wave Height (m): Test 11 Figure A.1 Overview of Difference in Significant Wave Height: Test 11 Figure A.2 1 Hs (m) A1 - A2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) B1 - B2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) C1 - C2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) D1 - D2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
0.5 Hs (m) E1 - E2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) F1 - F2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) G1 - G2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5 Difference in Significant Wave Height
Difference in Significant Wave Height (m): Figure A.3 Test 11 - Baseline 2 Speed (m/s) A1 - A2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) B1 - B2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) C1 - C2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) D1 - D2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
1 Speed (m/s) 0.8 E1 - E2 0.6 0.4 0.2 0 0 100 200chainage (m) 300
0.2 Speed (m/s) F1 - F2 0.15
0.1
0.05
0 0 100 200chainage (m) 300
0.2 Speed (m/s) G1 - G2 0.15
0.1
0.05
0 0 100 200chainage (m) 300 Baseline Current Speed Scenario Current Speed
Wave Induced Currents: Test 11 Figure A.4 4 Hs (m) A1 - A2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) B1 - B2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) C1 - C2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) D1 - D2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) E1 - E2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) F1 - F2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) G1 - G2 3
2
1
0 0 100 200chainage (m) 300 Baseline Significant Wave Height Scenario Significant Wave Height
Significant Wave Height (m): Test 12 Figure A.5 Overview of Difference in Significant Wave Height: Test 12 Figure A.6 1 Hs (m) A1 - A2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) B1 - B2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) C1 - C2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) D1 - D2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
0.5 Hs (m) E1 - E2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) F1 - F2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) G1 - G2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5 Difference in Significant Wave Height
Difference in Significant Wave Height (m): Figure A.7 Test 12 - Baseline 2 Speed (m/s) A1 - A2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) B1 - B2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) C1 - C2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) D1 - D2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
1 Speed (m/s) 0.8 E1 - E2 0.6 0.4 0.2 0 0 100 200chainage (m) 300
0.2 Speed (m/s) F1 - F2 0.15
0.1
0.05
0 0 100 200chainage (m) 300
0.2 Speed (m/s) G1 - G2 0.15
0.1
0.05
0 0 100 200chainage (m) 300 Baseline Current Speed Scenario Current Speed
Wave Induced Currents: Test 12 Figure A.8 4 Hs (m) A1 - A2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) B1 - B2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) C1 - C2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) D1 - D2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) E1 - E2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) F1 - F2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) G1 - G2 3
2
1
0 0 100 200chainage (m) 300 Baseline Significant Wave Height Scenario Significant Wave Height
Significant Wave Height (m): Test 13 Figure A.9 Overview of Difference in Significant Wave Height: Test 12 Figure A.10 1 Hs (m) A1 - A2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) B1 - B2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) C1 - C2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) D1 - D2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
0.5 Hs (m) E1 - E2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) F1 - F2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) G1 - G2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5 Difference in Significant Wave Height
Difference in Significant Wave Height (m): Figure A.11 Test 13 - Baseline 2 Speed (m/s) A1 - A2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) B1 - B2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) C1 - C2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) D1 - D2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
1 Speed (m/s) 0.8 E1 - E2 0.6 0.4 0.2 0 0 100 200chainage (m) 300
0.2 Speed (m/s) F1 - F2 0.15
0.1
0.05
0 0 100 200chainage (m) 300
0.2 Speed (m/s) G1 - G2 0.15
0.1
0.05
0 0 100 200chainage (m) 300 Baseline Current Speed Scenario Current Speed
Wave Induced Currents: Test 13 Figure A.12
Appendix B
Pre-Dredge Scenarios
Marsaxlokk Secondary Breakwaters
Appendix B. Pre-Dredge Scenarios
An additional test is included to enable assessment of the wave behaviour due only to the proposed fairway dredging activity. The main report already presents the Baseline test which included the fairway as a 25m wide and 5.5m deep channel passing through present day bathymetry. This ‘Pre-dredge Test’ is identical to that Baseline but excludes the dredged fairway. The wave climate due to the Pre-dredge test is presented in Figure B.1. The resulting changes in wave height are presented in Figure B.2 and Figure B.3. Pre-dredge wave induced currents are shown in Figure B.4.
Figure B.3 shows that the fairway increases wave height by 0.2m in the vicinity of the proposed 2b breakwater. This is the result of the side slopes of the dredged fairway causing wave energy to be redistributed, by refraction, from the deep water of the fairway channel to the shallower areas to either side of the fairway. This effect lowers wave heights in the fishing village haven by redirecting waves out of the fairway. It must be noted that these redirected waves cause a small increase at the rear of the fishing village haven as they are reflected back into the fairway and enter the haven. By carefully managing these reflected waves the wave climate inside the fishing village haven is successfully reduced. In the event that the fairway is not implemented for its full proposed length, i.e. beyond the proposed 2b breakwater and into the deep water at the centre of the bay, then this effect would be reduced and the opportunity to manage the approaching waves by redirecting them towards the proposed breakwaters and attenuate them is lost. The full implementation of the proposed fairway is therefore recommended.
R/3865/1 B.1 R.1583
4 Hs (m) A1 - A2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) B1 - B2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) C1 - C2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) D1 - D2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) E1 - E2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) F1 - F2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) G1 - G2 3
2
1
0 0 100 200chainage (m) 300 Baseline Significant Wave Height PreDredge Significant Wave Height
Significant Wave Height (m): Pre-dredge Test Figure B.1 Overview of Difference in Significant Wave Height: Figure B.2 Baseline - Pre-dredge 1 Hs (m) A1 - A2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) B1 - B2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) C1 - C2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) D1 - D2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
0.5 Hs (m) E1 - E2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) F1 - F2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) G1 - G2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5 Difference in Significant Wave Height
Difference in Significant Wave Height (m): Figure B.3 Baseline - Pre-dredge 2 Speed (m/s) A1 - A2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) B1 - B2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) C1 - C2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) D1 - D2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
1 Speed (m/s) 0.8 E1 - E2 0.6 0.4 0.2 0 0 100 200chainage (m) 300
0.2 Speed (m/s) F1 - F2 0.15
0.1
0.05
0 0 100 200chainage (m) 300
0.2 Speed (m/s) G1 - G2 0.15
0.1
0.05
0 0 100 200chainage (m) 300 Baseline Current Speed Scenario Current Speed
Wave Induced Currents: Pre-dredge Test Figure B.4
Appendix C
Frequent Wave Events (10 in 1 year): Tests 14 and 15
Marsaxlokk Secondary Breakwaters
Appendix C. Frequent Wave Events (10 in 1 year): Tests 14 and 15
At request, two further tests have been undertaken to quantify the behaviour of waves and the wave induced current in Il - Bajja ta’Marsaxlokk during more frequent wave events than the 1 in 50 year return period event used in all earlier tests. Specifically, there is a need to determine how different the wave induced currents are on a more frequent time-scale. Tests 14 and 15 have a 10 in 1 year wave applied to them. Test 14 is the baseline condition (no proposed breakwaters) while Test 15 applies the 10 in 1 year wave event to the baseline condition with the breach through the south quay. A 10 in 1 year return period event has a wave height of 0.99m in the vicinity of the existing damaged breakwater (ABPmer, 2007).
Test 14 Test 14 summary: This test considers the baseline arrangement (no proposed breakwaters) during a 10 in 1 year return period wave event. . Figure C.1 - significant wave height; . Figure C.2 - wave induced current.
With specific regard to the wave induced current flows, the 10 in 1 year return period wave results in the same pattern of wave induced current flow as the 1 in 50 year return period wave event, albeit with a reduced current speed compared to the currents induced by the 1 in 50 year return period event.
Test 15 Test 15 summary: This test considers the baseline arrangement (no proposed breakwaters) but with the breach through the south quay added during the 10 in 1 year return period wave event. . Figure C.3 - significant wave height; . Figure C.4 - overview of differences in significant wave height; . Figure C.5 - differences in significant wave height in Il - Bajja ta’Marsaxlokk; . Figure C.6 - wave induced current.
The results shown that no significant changes are apparent in the wave induced current circulation when the breach through the south quay is implemented.
R/3865/1 C.1 R.1583
4 Hs (m) A1 - A2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) B1 - B2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) C1 - C2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) D1 - D2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) E1 - E2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) F1 - F2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) G1 - G2 3
2
1
0 0 100 200chainage (m) 300 Baseline Significant Wave Height
Significant Wave Height (m): Test 14 Figure C.1 (baseline with 10in1 year wave event) 2 Speed (m/s) A1 - A2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) B1 - B2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) C1 - C2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) D1 - D2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
1 Speed (m/s) 0.8 E1 - E2 0.6 0.4 0.2 0 0 100 200chainage (m) 300
0.2 Speed (m/s) F1 - F2 0.15
0.1
0.05
0 0 100 200chainage (m) 300
0.2 Speed (m/s) G1 - G2 0.15
0.1
0.05
0 0 100 200chainage (m) 300 Baseline Current Speed
Wave Induced Currents: Test 14 Figure C.2 (baseline with 10in1 year wave event) 4 Hs (m) A1 - A2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) B1 - B2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) C1 - C2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) D1 - D2 3
2
1
0 0 100 200 300 400 500 600chainage (m) 700
4 Hs (m) E1 - E2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) F1 - F2 3
2
1
0 0 100 200chainage (m) 300
4 Hs (m) G1 - G2 3
2
1
0 0 100 200chainage (m) 300 Baseline Significant Wave Height Scenario Significant Wave Height
Significant Wave Height (m): Test 15 Figure C.3 (baseline + breach 10in1 year wave event) Overview of Difference in Significant Wave Height: Test 15 Figure C.4 (baseline + breach with 10in1 year wave event) 1 Hs (m) A1 - A2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) B1 - B2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) C1 - C2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
1 Hs (m) D1 - D2 0.5
0 0 100 200 300 400 500 600chainage (m) 700 -0.5
-1
0.5 Hs (m) E1 - E2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) F1 - F2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5
0.5 Hs (m) G1 - G2 0.3 0.1 chainage (m)
-0.1 0 100 200 300 -0.3 -0.5 Difference in Significant Wave Height
Difference in Significant Wave Height (m): Figure C.5 Test 15 (10in1) - Baseline + breach (10in1) 2 Speed (m/s) A1 - A2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) B1 - B2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) C1 - C2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
2 Speed (m/s) D1 - D2 1.5
1
0.5
0 0 100 200 300 400 500 600chainage (m) 700
1 Speed (m/s) 0.8 E1 - E2 0.6 0.4 0.2 0 0 100 200chainage (m) 300
0.2 Speed (m/s) F1 - F2 0.15
0.1
0.05
0 0 100 200chainage (m) 300
0.2 Speed (m/s) G1 - G2 0.15
0.1
0.05
0 0 100 200chainage (m) 300 Baseline Current Speed Scenario Current Speed
Wave Induced Currents: Test 15 Figure C.6 (baseline + breach with 10in1 year wave event)