Shoreline Management of the Dubai Coast - DHI · PDF fileShoreline Management of the Dubai...

COPEDEC VII, 2008, Dubai, UAE Paper No: M-15

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Shoreline Management of the Dubai Coast by

K. Mangor1, Gary Mocke2, Claudia Giarrusso3, Francois Smit4, R. Bloch5, J. Fuchs6, U. Lumborg7 and S. L. Niemann8

ABSTRACT

DHI has performed the project: PJ 10018: “Management Guidelines for Dubai Coast” on behalf of the Coastal Management Section (CMS) of Dubai Municipality (DM) during the period 2005 to 2007, refer DHI 2007. The background for this project is the wish by CMS to obtain up to date and accurate information on hydraulic and coastal conditions as basis for the management of the coast. The paper presents the main results of this project with emphasis on the comprehensive numerical modelling, discussion of the results and the philosophy for developing a new coastline which is in harmony with the drastically changed coastal conditions.

1. INTRODUCTION

The content of this paper is strongly related to the main technical objectives of the project PJ 10018, which are: Assessment of the current state of the Dubai Coast Assessment of impacts on the coastal area caused by existing and future developments Perform vulnerability and risk classification of the coast in relation of coastal erosion, coastal

flooding and beach degradation Identification of possible mitigation measures including sand bypass operations and their cost

implications (lifecycle cost) Identification of possibilities for improvement of the coastal amenities along the coast and of

possible new development possibilities Identification of requirements for monitoring programmes Definition of setback lines for future development Furthermore, there are also project objectives related to statutory conditions but these will not be part of this paper.

2. GENERAL DESCRIPTION OF THE DEVELOPMENT IN THE COASTAL AREA

The development of Dubai’s coastal area started in the 1970ies and has accelerated ever since. The huge and fast development is summarized in the following and presented in Figure 1:

1971-1990: Construction of the two main ports: Port Rashid (compl. in 1972) and Jebel Ali Port (compl. in 1983), numerous seawater outfalls for DUBAL and DEWA and construction of marinas (Al Mina Al Seyahi, Umm Sequim 1 and 2 marinas and Jumeirah Fishing Harbour).

1990-2000: Several beach hotels being constructed, such as Jumeirah Beach Hotel, Ritz Carlton, Oasis Beach Resort, Hilton and the One and Only Royal Mirage etc. Numerous high-end residential schemes were constructed. All developments were concentrated in the coastal area.

After 2000: The iconic Burj Al Arab Hotel constructed on an artificial island was finalised in 2000. The construction of the famous Offshore development Schemes (ODS) was initiated in 2000. Schemes under construction in 2007 are: Palm Jumeirah (1), Palm Jebel Ali (2), The World (4) and Palm Deira (3); Dubai Waterfront (13) is in its initial phase of construction. Furthermore, Jebel Ali Port is being 1 M.Sc., Chief Engineer, DHI, Agern Allé 5, DK-2970 Hørsholm, Denmark, Tel: +45 45169200, [email protected] 2 Ph.D., Head of Coastal & Oceans Group, Worley Parsons Infrastructure, [email protected] 3 Coastal Eng. Specialist, Coastal Man. Section, Dubai Municipality, U.A.E., Tel: +971 4 229 7125, [email protected] 4 Coastal Engineer, Worley Parsons Infrastructure, francois.smit@ worleyparsons.com 5 Ph.D., Urban and Regional Planner, Independent, [email protected] 6 M.Sc., Head of Projects, DHI, [email protected] 7 Ph.D., Physical Geographer, DHI, [email protected] 8 Ph.D., Coastal Engineer, DHI, [email protected]

mailto:[email protected]








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expanded. An initial assessment of the effects of these developments on the coast is discussed in Smit et al (2005).

Figure 1: The ODS under development along the Dubai Coast. Nakheel’s home page. Segments shown in blue

The hydraulic and coastal conditions along the coast of Dubai have been modelled for the six development cases presented in Table 1

These cases have for simplicity been merged into four development states as presented in Table 2. Only the development states will be described in this paper. The coast has also been divided into Segments I through IV as shown in Figure 1.

Development cases

Offshore Development Schemes Case 1 Case 2 Case 3 Case 4A

Case 4 Case 5

No ODS x Palm Jebel Ali x X x x x Jebel Ali Port Expansion Stage 1 x Jebel Ali Port Expansion Final x Palm Jumeirah x X x x x The World X x x x Deira Sea Corniche X x x x Palm Deira x

Table 1 : Summary over development cases which have been modelled

Development states

Offshiore Development Schemes

Pre ODS

Historic Current/

Near future

Future No ODS x Palm Jebel Ali X x x Jebel Ali Port Expansion Stage 1 x Jebel Ali Port Expansion Final x Palm Jumeirah x x x The World x x Deira Sea Corniche and Palm Deira x x

Table 2 : Summary over development states

It is noted that a development state including Dubai Waterfront has not been studied as this development was launched later than the start of the study. It should also be noted that new developments continue to emerge.

It is evident form the above description that the Dubai coastline has been divided in a series of individual cells which do not exchange sediments with the neighbouring cells. The shorelines in the

Seg. I Seg. II Seg. III Seg.IV


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coastal cells will tend to stabilize themselves in equilibrium orientations, which are the orientations providing zero net littoral transport. This means that a shoreline in a cell will be unstable if the orientation of the shoreline deviates from the equilibrium orientation. The construction of the ODS has drastically changed the wave conditions and thereby also the transport and equilibrium orientations in the littoral cells. This has given rise to very drastic changes in some of the littoral cells dependent on the location of the cell relative to the ODS and relative to the main wave direction. There are examples of all types of impacts in relation to the changes in wave exposure and equilibrium orientations. The impact can be in the form of less or more transport and even reversed transport, which of course has drastic influence on the stability of the shoreline sections leading to new erosion and deposition patterns. However, these new instability conditions can be mitigated by introducing new shoreline development schemes, which are likely to appear anyway in connection with the many new coastal development schemes and expansion of marinas etc. This means that the coastal response to the ODS is a challenge which can be managed through shoreline management schemes with good and stable artificial beaches. Furthermore, there are impacts related to change in wave exposure, with sheltered areas designated into categories of moderately or very protected, which, especially for the very protected beaches, may lead to the risk of beach quality degradation. This situation is very difficult to mitigate other than by optimizing/minimizing the schemes giving rise to this wave shelter. This may constitute a serious hindrance for further offshore developments. All these conditions and impacts were modelled using DHI’s coastal modelling suite as described in the following.

3. GENERAL DESCRIPTON OF THE COASTAL ENVIRONMENT IN DUBAI AND STUDY APPROACH

The present section contains a short description of the most important hydraulic and coastal data, which is of importance for the littoral transport and shoreline stability conditions along the coast of Dubai as well as the study methodology.

Waves Dubai is located in the SE part of the Arabian Gulf and is mainly exposed to the predominant Shamal waves from NW-erly directions, see Figure 2.

Figure 2: Overall offshore wave conditions for Dubai (P2987)

The wave climate along the Dubai coast has been studied in detail by numerical modelling applying the following models:

Offshore wave model Offshore wind and wave data has been extracted from the PERGOS model. PERGOS is a comprehensive metocean study of the Gulf developed by Oceanweather and DHI. The wind and wave hindcasts were all made with basin-wide grids of spacing .0625 degrees in latitude and longitude (7 km), nested within coarser grid systems covering the Gulf of Oman and the Arabian Sea. 2-D water


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levels (including surge and tide) and currents have been run with DHI’s MIKE 21 flexible mesh model using a mesh resolution better than 7 km. The wave model incorporates third-generation physics (OWI3G version 52, half friction). Time series of wind and wave data for 12 years (Jan. 1993 through Dec. 2004) were obtained in 4 locations, see Figure 3. It is seen that WNW-erly winds and waves are dominating in the Dubai offshore waters.

Figure 3: The 4 extraction points for PERGOS offshore wind and wave data (left), a wind

rose (right upper) and a wave rose (right lower) for point P2621 Nearshore regional wave model and bathymetry The nearshore waves along the entire Dubai coast has been established through extensive numerical modelling utilizing the flexible mesh wave model MIKE 21 SW, which is a fully spectral wave model for simulating the evolution of the 2-dimensional wave energy spectrum with time. The model was calibrated against measured waves at nearshore locations. Transformation of the waves from offshore to nearshore was performed by simulating 400 wave events for each of the six cases. An example of the used regional model grid is presented in Figure 4 and a more detailed picture of the same mesh is presented in Figure 5.

Figure 4: Flexible model mesh and bathymetry for Case 3


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Figure 5: Flexible mesh in Segment III for Case 3

The bathymetry in the area is also shown in Figures 3, 4 and 5. It is seen that there is a fairly shallow area off Segment I, which is due to coral formations in this area (Marine Sanctuary). The bathymetry off the other Segments shows a steeper seabed profile and the seabed consists generally of sandy deposits. An example of the wave pattern for an event at the model boundary (P2621): Hs = 2.25 m, Tp = 8.5 s and MWD = 295° N for Case 3, Segment III is presented in Figure 6.

Figure 6: Close-up of wave conditions along Segment III for Case 3. Wave conditions at model

boundary (P2621): Hs = 2.25 m, Tp = 8.5 s and MWD = 295° N It is noted that there is a considerable impact of Palm Jumeirah and The World on the wave conditions along the coast of Segment III.


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The wave conditions along the entire coast have been extracted in points at approx. 1 km distance at water depths of about 6 m for all the 6 x 400 modelled wave events and statistical analysis have been performed resulting in approx. 6 x 60 wave roses representing the wave conditions along the coast for all six cases. An example of the results of this comprehensive analysis is presented in Figure 7 showing the wave roses along the coast of Segment 3 for the Current/Near future state.

Figure 7: Selected wave roses for Segment III for the Current/Near future state Again, the impact of Palm Jumeirah (PJ) and The world (TW) is very clearly seen in the wave roses. The following characteristics are noted: NE of PJ and TW: Predominant waves are turned clockwise and the wave exposure is reduced,

the reduction in exposure is considerable in lee of PJ. This is a very drastic change as it results in reversal of the littoral transport in these areas

SW of TW: Predominant waves are turned counter-clockwise and the wave exposure is reduced, but there is still enough wave exposure to maintain a good beach

The implication of these new wave conditions are analysed further in the following.

Tides and storm surges The tides in Dubai are predominantly semi-diurnal with a Spring Tidal Range: HHHW – MLLW ~ 1.2 m. Water levels and tides in this project are referred to Dubai Municipality Datum (DMD), which is identical to LAT. Chart Datum (CD), which is the basis for Sea Charts, is 0.1 m higher than LAT. Mean Sea Level (MSL) is + 1.13 m DMD or +1.03 m CD. The extreme water levels have been estimated as follows: 1-year return period: +2.10 m DMD 50-year return period: +2.68 m DMD 100-year return period: +2.78 m DMD

Wave transformation

28a

31

35

38

41a

44

Offshore

Offshore


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Flooding levels Three extreme water levels are computed: The Still Water Level (SWL) the Flooding Level (FL) and the Wave Impact Level (WIL). These levels are calculated for all the computation points along the coast and consist of the following components:

1. Estimated extreme water levels, including the effect of tides and surges (see above) 2. Allowance for the impact of the ODS on design water levels 3. Allowance for the influence of sea level rise 4. Design Still Water Level: [1 + 2 + 3] 5. Wave set-up 6. Wave run-up. This includes wave set-up and wave swash 7. Flooding Level (FL): [1 + 2+ 3 + 5] 8. Wave Impact Level (WIL): [1 + 2 + 3 + 6]

An assessment of the impact of the ODS on FL and WIL has been performed. The FL and the WIL are composed of the components described in Table 3.

Water levels

Excl. imp. of waves Incl. imp. of waves Components

Still Water Level SWL

Flooding Level FL

Wave Impact Level, WIL = SWL+ R2%

Extreme water level (50-year recurrence) 2.68mDMD

Allowance for impacts from ODS +0.3m

Allowance for Sea Level Rise, year 2050 +0.2m Wave set-up Not incl. Incl., but varying Incl., but varying Wave run-up (R2%) Wave swash Not incl. Not incl. Incl., but varying

Defines the line SWL +3.2m DMD Flooding line Wave impact line Table 3: Overview of components of design water levels and water lines

4. COASTAL IMPACT OF THE OFFSHORE DEVELOPMENT SCHEMES It is evident from the description of the wave conditions along the coast of Dubai that there will be a considerable impact of the ODS on the coastal conditions. The following parameters have been analysed: Extreme wave conditions Extreme water levels, Flooding Levels and Wave Impact Level Wave exposure, coastal classification and beach degradation classification Extension of the littoral zone expressed by the Closure Depth, dc Equilibrium orientation of the shoreline Stability of the shoreline expressed in 20-year potential shoreline evolution These items will be addressed in the following through examples of the impacts along Segment III. Results are presented for the Pre ODS and for the Current/Near future state, whereby the impacts of Palm Jumeirah and The World are clearly demonstrated. Extreme wave conditions The distribution in the 50-year recurrence significant wave height along Segment III is presented in Figure 8 for the Pre ODS state and the current/near future situation. It is noted that the 50-year recurrence wave data are only qualified estimates and for illustration purposes only.


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Figure 8: 50-year recurrence significant wave heights for Segment III for the Pre ODS and the

current/ near future state It is seen that there is a drastic reduction in the wave height from about Hs50y = 3.0 – 4.0m outside the sheltered area to Hs50y = 1.1m in the centre of the sheltered area behind The World. Flooding Levels and Wave Impact Levels The variation in Flooding Levels and Wave Impact Levels along Segment III is presented in Figure 9. “Wave impact level” includes wave run-up. It is noted that the flooding levels and wave impact levels are only qualified estimates and for illustration purposes only. It is seen that there is a minor impact on the flooding level and a major impact in the wave impact level due to the presence of The World (and Palm Jumeirah) along Segment III.


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Figure 9: Flooding Level and Wave Impact Level for Segment III for Pre ODS (upper) and current/near future state (lower)

Wave Exposure, coastal and beach degradation and classification The variation in the wave exposure, expressed by Hs12h/y, along Segment III is presented in Figure 10.

Figure 10: Variation of Hs,12h/yr along Segment III of the Dubai Coast for Pre ODS and

current/near future state Again, it is evident that there is a great impact in the wave exposure of the ODS (especially Palm Jumeirah and The World) along Segment III. The wave exposure is used as basis for classification of


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the coastal profiles according to the wave height limits presented in Table 4. The coastal classification is used as the basis for the beach degradation classification, which is also shown in Table 4. Coastal Classification Wave height limits Risk of Beach Degradation Exposed (E) 3.0m < Hs,12h/y Moderately Exposed (ME) 1.0m < Hs,12h/y < 3.0m

Not vulnerable to beach degradation

Moderately protected (MP) 0.5m < Hs,12h/y < 1.0m Very Protected (VP) 0.0m < Hs,12h/y < 0.5m

Vulnerable to beach degradation, critical for recreational beaches

Table 4: Coastal classification and beach degradation classification

It is seen that there is a risk for beach degradation in the area immediately NE of Palm Deira whereas the area sheltered by The World is just on the limit for being critical.

Closure Depth The variation in the closure depth, dc, along Segment III is presented in Figure 11.

Figure 11: Estimated closure depths, dc, for Segment III for Pre ODS and current/near future

state Again, it is evident that there is a great impact on closure depth of the ODS (especially Palm Jumeirah and The World) along Segment III. The width of the active littoral zone is reduced correspondingly.

Change in the Equilibrium Orientation The variation in the equilibrium orientation along Segment III is presented in Figure 12 and Figure 13. The equilibrium orientation is a very useful tool for evaluation of the following conditions:

The stability of the shoreline in a littoral cell: The shoreline will be unstable if the equilibrium orientation deviates from the orientation of the present shoreline as the shorelines in the littoral cells will always tend to develop towards the equilibrium orientation

As a guide for developing shoreline management schemes: A shoreline management scheme is a recreational scheme consisting of coastal structures and new sections of artificial beaches. The artificial beach sections shall be built with the equilibrium orientation


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Figure 12: Estimated equilibrium beach orientations along Shoreline Segment III.

Locations 28 to 45. Pre ODS and current/near future state

Figure 13: Estimated equilibrium shoreline orientations along shoreline Segment III for the

Pre ODS state (Blue arrows) and for the current/near future state (Red arrows). Arrows indicate the normal to the equilibrium orientation


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A very interesting phenomenon is observed, as previously discussed in Smit et al (2005). The impact of The World caused a counter-clockwise rotation of the equilibrium orientation SW of the scheme and a clockwise rotation NE of the scheme, respectively. Furthermore, a drastic clockwise rotation immediately NE of Palm Jumeirah is noted. This is due to the shelter provided by Palm Jumeirah. These changes in equilibrium orientation cause drastic changes in the littoral transport as well as in the stability conditions for the affected shoreline sections. Change in the Shoreline Stability The above documented changes in wave conditions have resulted in drastic changes in the littoral transport as well as in the potential shoreline evolution along Segment III. This is demonstrated by the following results of regional shoreline evolution modelling as presented in Figure 14, which presents the conditions in the northern part of Segment III for the Pre ODS state and for the Current/near future state, respectively. The difference between the two potential 20-year shoreline evolutions thus represents the impact of The World.

Figure 14: Predicted 20-year shoreline positions for Northern Part of Segment III for historic

state and current/near future state The following interesting phenomena are seen:

Jumeirah Fishing Harbour to Jumeirah Open Beach. The introduction of The World has caused a drastic decrease in the wave exposure and a reversal of the net littoral transport direction (from NE-ward to SW-ward) as well as a reduction in the net transport capacity. This results in a completely different potential shoreline evolution in the two states. Before the construction of The World, the potential 20-year shoreline evolution resulted in erosion in the SW-ern end and accretion in the NE-ern end of this Section. However, following the construction of The World, this has completely changed resulting in accretion in the SW-ern end and erosion in the NE-ern end. Consequently, the impact of The World results in a completely new pattern in the shoreline evolution

The stretches “3 breakwaters” to Al Rais Spur (Off Jumeirah Beach Park, Dubai Ladies Club and Jumeirah Beach Club) and Al Rais Spur to Jumeirah Fishing Harbour show similar patterns of reversed shoreline development pattern


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5. RISK REGISTER FOR EROSION, FLOODING AND BEACH DEGRADATION Erosion risk classification The results of the 20-year potential shoreline evolution modelling have been used as basis for analysis of vulnerability and risk for erosion along Dubai’s coast. Areas vulnerable to erosion have been classified at two levels: Immediate situation, requiring immediate protection: Where erosion is greater than 20m within the

first two years Long-term situation, requiring comprehensive shoreline management mitigation measures:

Where erosion over a 20-year period is in conflict with Coastal Development Control Line/present Building Line

The differences between the two situations are: The risk register for the immediate situation identify areas, which are under fast erosion, and where immediate action is consequently required in order to: Prevent loss of beaches Maintain status quo Prevent future damages Gain time for implementation of the optimal long-term scheme The proposed measures are of a temporary nature. Generally, nourishment is recommended until more permanent schemes can be designed and implemented. The risk register for the long-term situation identify areas, which are under long-term erosion leading to loss of beach resources or to damages on coastal facilities and assets (housing, infrastructure, etc) and which consequently require undertakings in the form of implementation of shoreline management schemes providing long-term stable and sustainable solutions. The used vulnerability and risk classification is presented in Table 5.

Situation Erosion status

Land use Present Protection status

Risk category Type of recommended intervention

Rural Not prot. 2 yr erosion < wmin Urban All

Vulnerable to erosion but not critical

None

Rural Not prot. Not critical presently Impose setback line as relevant Not prot. Critical to damage

on fixed facilities Nourishment

Protected and exposed

Critical as beach is lost

Immediate nourishment to regain sandy beaches, however, no action required to preserve Status Quo Im

med

iate

situ

atio

n

2 yr erosion > min. beach width wmin

Urban

Buried protection

Critical to loss of beach

Nourishment

Rural Not prot. 20 yr erosion + var. < wmin

Urban All

Vulnerable to erosion but not critical

Impose setback line as relevant

Rural Not prot. Not critical presently Impose setback line as relevant

Not prot. Critical to damage on fixed facilities

Shoreline management scheme

Protected and exposed

Critical as beach is lost


Long

- ter

m s

ituat

ion

20 yr erosion + var. > minimum beach width wmin

Urban

Buried protection

Critical to loss of beach



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Table 5 : Overview over type of proposed protection intervention as function of risk classification, land use and protection status of eroding coasts in Dubai

Overview of the stretches under immediate erosion risk/long-term erosion risk in Segment III are presented in Figure 15 as examples of the performed vulnerability and risk classification, which was performed for the entire Dubai Coast.

Figure 15: Short-term and long-term erosion risk classification for Segment III Flooding risk classification

The A vulnerability and risk classification for flooding has been prepared taking the following items into account: The level of the hinterland relative to the Flooding Level (FL) The protection status of the section, ie the level of the sea defence/beach berm relative to the FL

and to the Wave Impact Level (WIL) The type of the hinterland, rural or developed The size of the immediate hinterland areas, which are lower than the FL: Small [corresponding to

a few housing lots (width of low area < 50m) or large (width of low area > 50m)]

The used vulnerability and risk classification for flooding is presented in Table 6. The risk of a Tsunami of any significance along the Dubai Coast has been assessed as very small. The impacts of tsunamis have consequently not been included in the present flooding analysis. The established FL and WIL are compared with levels extracted from the 2003 Digital Terrain Model (DTM) provided by DM. The locations of the thus established lines of FL and WIL-points are presented in Figure 16 with the 2005 satellite image as background. WIL-points are locations along selected profiles to which wave impact can be expected for a 50-year recurrence event. Low-laying areas further into the hinterland lower than FL, have also been presented in these figures. Characteristic profiles have also been extracted from the DTM for all the sections and cells along the coast, where after the different sections have been classified in relation to risk of flooding. It should be noted that the DTM is from 2003. It is known that many changes in the coastal area have taken place since 2003.

Vulnerable to erosion but not criticalNot critical presently

Critical as beach is lostCritical to loss of beach

Critical to damage on fixed assetsNot classified

Short term (2 years)

Long term (20 years)

Vulnerable to erosion but not criticalNot critical presently

Critical as beach is lostCritical to loss of beach

Critical to damage on fixed assetsNot classif ied


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Level of

hinterland: LH

Protection status and level of sea defence (SD)*:

LSD

Illustration of situation

Occupation/ size of low-lying hinterland

Risk category and marking

LH > WIL

LSD > WIL

All types No risk

LH

>FL LH < WIL

Low protection FL < LSD < WIL

All types No risk of flooding, vulnerable to wetting of hinterland

Rural/all sizes Not critical as flooding of backland is a natural process

Urban/small

Moderately critical as potential flooded area is small

Low protection FL < LSD < WIL

Urban/large

Risk of moderate flooding if sea defence is stable, risk of major flooding if sea defence is breached

Critical as major area may be flooded in case of breach of sea defence, check status of sea defence

Rural

Not critical, vulnerable to major flooding, impose dev. Restrictions

Urban/small

LH < FL

No protection LSD < FL

Urban/large

Critical to flooding damage, introduce sea defence

Note: A sea defense could be a beach berm, a dike or a seawall. For the computation of the WIL, a natural beach profile has been assumed, which corresponds to the presence of a beach berm in term of sea defense type

Table 6: Vulnerability and risk classification for flooding

Figure 16: Lines of FL and WIL-points as well as low laying areas for Segment III on basis of

DTM from 2003, shown on satellite image from 2005


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Beach degradation classification The Gulf beaches in Dubai are by nature of a very good recreational quality due to the natural wave exposure and due to the good quality natural beach sand available in the area. However, the wave exposure has been reduced along several coastal stretches due to the shelter provided by the many coastal and offshore development schemes as described in Section 4. An illustration of the importance of wave exposure is presented in Figure 17.

Figure 17: Difference between beach quality for exposed and very protected beaches

Stretches belonging to the category Moderately Protected but especially the category Very Protected are vulnerable to beach degradation. The beach degradation for Segment III is presented in Figure 18.

LEGEND: Red: Moderately Exposed – no risk of beach degradation Yellow: Moderately/very protected – critical to beach degradation

Figure 18: Coastal and beach degradation classification It should be noted that a major part of Segment III is just on the limit of being critical to beach degradation because of the shelter from The World, see Figure 10. The risk of beach degradation is considered to be one of the major risks for the mainland beaches in Dubai as more ODS’s are being developed and because it is very difficult to make any remedial measures to compensate for this risk, other than refraining from developing more ODS. 6. REGULATIONS

Land and Sea Zoning The “Regulations and Procedures for Dubai Coastal Zone –“, Decree No 22 (D22-R&P), refer DM (2004), establishes the requirements for all natural and legal persons, including public authorities, to

Mamzar Beach Park

Exposed Protected

Mamzar Lagoon


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obtain a “No-Objection Certificate” (NOC) from DM, before any construction, dredging and excavation activities are initiated in the coastal zone. The D22-R&P document is presently (2007) under revision. The D22-R&P defines the Coastal Zone (CZ). In accordance with a map accompanying D22-R&P, Dubai’s CZ is defined as the area between the point roughly 1km inland of the Coastal Development Control Line to a seaward limit 10 nautical miles offshore. In addition, the Decree’s zone of regulation covers the entire extent of Dubai Creek as well as Al Mamzar lagoon and any other excavated water connected to the Arabian Gulf. In D22-R&P, three regulation zones for implementation of the Decree are further defined:

Zone I: Marine Development Zone (MDZ) Zone II: Coastal Development Zone (CDZ) Zone III: Coastal Resource Zone (CRZ)

Sector requirements

The special characteristic of the CZ is that it is exposed to the forces of the marine environment to a higher extent than other areas, which expresses itself in the following phenomena of importance for the development in this zone: Coastal erosion Sedimentation and accumulation of sand along the coast Flooding of low-laying areas Changes in the quality of the beach

Such phenomena will cause conflicts with the ongoing development in the CZ and the development in the CZ will impact on the phenomena. The best way to handle such potential conflicts is to use different types of regulatory measures by which the potential conflicts can be avoided. DM has introduced the following regulations with the purpose of minimising the problems and protecting the marine and coastal environment: Introduction of Control Zones according to D22-R&P The requirement for a NOC before construction activities can be initiated according to D22-R&P The requirement for EIA according to Order No 61 of 1991 on the Environmental Protection

Regulations in the Emirate of Dubai and Guideline No 53: Environmental Impact Assessment Procedures (1995)

The issuing of Set-back requirements, see below Guidelines for development activities in the CZ, refer: Coastal Development Guidelines (scheduled

release 2008)

Setback Line The setback line is also referred to as the Coastal Development Control Line (CDCL), which is the line separating the Coastal Development Zone from the Marine Development zone. Coastal developments should not take place beyond the setback line (CDCL). Any construction or development activity taking place within the CDZ and MDZ requires a NOC form the General Projects Department of DM. It is noted that the Department shall not issue a NOC for any activity if the activity will have a significant adverse impact on the sandy beaches/marine environment of Dubai without a mitigation programme approved by the Department. Such impacts shall be thoroughly documented through the issue of an Env. Imp. Statement (EIS) or an EIA Report (EIR). The philosophy behind the concept of a setback line is to avoid conflicts between developments in the Coastal Development Zone (CDZ) and the active morphology of the coastal area within a certain time horizon. The coastal area is defined as the area influenced by the coastal morphological processes and consists of the coast, the shore and the shoreface. The general goals behind introducing a setback line are the following: To avoid conflicts between existing and new coastal developments and a receding shoreline To allow for a certain natural variability of the shoreline due to seasonal variations and extreme

events Allowance for a vacant backshore area as a buffer and to provide an area, where natural

backshore processes can take place, such as dune formation Allowance for changes caused by new ODS’s or similar, which may be developed in the future


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The following contributions have been taken into consideration in the evaluation of the setback line distance: 20-year shoreline development Sea level rise Variability in the location of the shoreline due to cross-shore as well as longshore processes Allowance for vacant backshore area Allowance for changes caused by future ODS

This analysis has resulted in the setback line distances presented in Table 7.

Type of backland Setback line distance [m]

Comments

Rural area 300 Urban 60 Industrial 40

Or existing line of facilities/assets if setback line is behind this line

Developed area Artificial beach 60

Note: Distance from 2006 coastline (+ 1.62m DMD)

Table 7 : Setback line distances [m] The setback line for the area between Umm Suqeim 1 and 2 harbours is presented in Figure 19.

Figure 19: Setback line and Coastal Development Zone in the area between Umm Suqeim 1

and 2 harbours

7. SHORELINE MANAGEMENT SCHEMES

A shoreline management scheme (SMS) is very similar to a coastal development scheme; however, it is typically a public-financed scheme built to compensate coastal instability and to rehabilitate and expand the beach and marine elements in an area. A SMS consists typically of the following marine elements: Artificial beaches and beach reclamations, typically in the form of realigning an existing beach to fit

the equilibrium orientation Terminal structures to prevent loss from the artificial beaches, maybe combined with marinas or

lagoon openings; however, these elements are typically part of a private scheme


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Artificial public lagoons, either built into the sea in connection with beach reclamations or excavated into the mainland

Lagoon openings

The Mamzar Beach Park and the Jumeirah Open Beach are typical examples of public shoreline management schemes. The main “art” for developing successful SMS along the Dubai Coast is to utilize the possibilities in an area so that: Coastal instability problems are “permanently” solved, e.g. by building new beaches in the

equilibrium orientation Combining the requirements for terminal structures with other demands in the area such as plans

for expanding marinas, the need for new lagoon openings or the need for viewing and promenading facilities, etc. It is very important to use the concept of multi-functional facilities for the development of new coastal structures in Dubai due to the very limited space and due to the huge demand for recreational facilities

A typical example of a SMS is presented in Figure 20 below.

Figure 20: Example on Shoreline Management Scheme for the Sunset Beach and the area

between Umm Suqeim 1 and 2 Harbours in connection with a major expansion of the US2 Harbour

8. GUIDELINES FOR OFFSHORE DEVELOPMENT SCHEMES

There is in principal two main marine issues to consider: The internal functionality of the scheme and the requirement for sustainable development in general.

Functionality of the Scheme The potential attractive marine elements of an offshore development schemes are the following:


20

Protected artificial water bodies or lagoons. Such lagoons provide a calm water environment, which

provides possibilities for development of attractive recreational facilities facing a semi-open water body

Good water quality in the lagoon is of paramount importance for the recreational value of the lagoon

Possible external waterfront perimeters shall be designed to provide protection and possibly other recreational functions. There are in principal two different kinds: Pure protection is typically obtained by rubble mound structures which, however, have no

recreational quality There is also the possibility to include sections of pocket beaches in the outer perimeter, which

can provide very attractive beach environments The internal waterfront perimeters inside the lagoon shall be selected to provide the best possible

recreational functions, whereas protection is only a secondary requirement inside the lagoon. There are in principal the following types of perimeter structures: Rubble mound slopes, vertical walls and bulkheads, stepped slopes, piled decks and piers in concrete or wood, floating piers and sandy beaches However, it is often a problem to obtain a good quality beach in a lagoon environment as discussed in Section 5 under “Beach degradation classification”

Sustainable Development of an ODS

Securing sustainability of an ODS requires integration of horizontal (sector) and vertical (spatial) requirements. This highlights the importance of sufficient coordination between all involved authorities and stakeholders, especially for projects in the CZ. It is consequently important that all NOC and EIA procedures are followed for these schemes.

The general marine requirements for obtaining sustainability of an ODS are outlined in the following: Secure that the scheme does not impact the flushing and water quality in the adjacent area, neither

during construction nor during the operation phase. Optimise the scheme for minimisation of possible impacts and/or propose and implement mitigating measures as required

Secure that the scheme has a minimum impact on coastal conditions on the adjacent coast in respect of coastal stability and beach degradation. Optimise the scheme for minimisation of possible impacts and/or propose and implement mitigating measures as required

9. REFERENCES DHI (2007): Management Guidelines for Dubai Coast, Preliminary Design Report, Final Draft of September 2007, Project PJ 10018 for Dubai Municipality. DHI (2007): Coastal Development Guidelines, PJ 10018 – Management Guidelines for Dubai Coast, First Draft of October 2007 Dubai Municipality (2004): “Regulations and Procedures for Dubai Coastal Zone Construction and Sand Excavation, Dredging and Filling”, Pursuant to Dubai Governors Decree No. 22 of 2001, by Coastal Management Section, General Projects Department of Dubai Municipality, Revision No: 3.0 of June 2004. Smit, F, Mocke, G P, Al-Zahed, K (2005). Quantifying and managing the coastal response to major offshore developments in Dubai. Proceedings of Coastal Zone 05, New Orleans, USA.

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