A Bay in Equipoise

A STRATEGY TO BALANCE DEVELOPMENT AND NATURAL PROCESS IN BENOA BAY, BALI

Student Thesis Advisor

: Laura Rulianto : Scott Jennings Melbourne

image : KALA BENOA (full movie). (2016). YouTube.

Master of Landscape Architecture | The University of Hong Kong | Thesis 2016

FRONT MATTERS

FRONT MATTERS

TABLE OF CONTENTS

FRONT MATTERS

Cover Page & Table of Content

POSITIONING Thesis Statement 05 Global Bay Comparison 06 Context 07

The Significance of the Bay

08 Past, Now, and Future 09

Research & Design Methodology and Proposed Project Brief

24 SPECULATION

Fieldwork

26 Population Study

27

Bay Data Visualization

28

Tidal Study Model

34

Site Selection Methodology

35 General Strategy 37

Watershed Analysis & Design Proposal

Mati Watershed

38

Sama Watershed

43

Bualu Watershed

48 Turtle Island 53 APPENDIXES

THE UNIVERSITY OF HONG KONG DIVISION OF LANDSCAPE ARCHITECTURE FACULTY OF ARCHITECTURE MASTER OF LANDSCAPE ARCHITECTURE | 2016

A BAY IN EQUIPOISE A STRATEGY TO BALANCE DEVELOPMENT AND NATURAL PROCESS IN BENOA BAY, BALI

Records of Final Panels

59 Bibliography 63

Acknowledgement

64

Statement of Academic Integrity

65

thesis supervisor Scott Jennings Melbourne submitted by Laura Rulianto contact annalaura@connect.hku.hk

A BAY IN EQUIPOISE | A strategy to balance development and natural process in Benoa Bay, Bali

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POSITIONING

POSITIONING

THESIS STATEMENT

A Bay in Equipoise Benoa is a shallow intertidal bay located at the southern part of Bali, Indonesia, on the seashore of Indian Ocean. Besides its strategic location, the bay has a rich ecosystem and is a place for diverse activities and infrastructures. It has recently been a subject undergoing intense study in Indonesia because of its high environmental problems and social conflicts.

Current bay condition shows the imbalance state of development and natural process. Researches showed a huge increase rate of sedimentation at the bay. The bay sedimentation is already too much right now that the bay is not effective for many activities. Most of the severe bay sedimentation is a result of surrounding human interventions that underestimate the importance of preserving the nature. If this continues, the surrounding ecosystem, community, and economy could be terribly affected. More mangroves, sea grass, and corals would die; locals would lose their jobs; water tourism would also be gone.

I believe that now it is crucial to think of how to balance the bay in order to maintain the environmental sustainability. Development should be focused not only on accelerating the economic growth but more importantly also on environmental sustainability in which human can get the benefits in the long term. This proposal offers some strategies to create a healthier and more balanced bay that can be a valuable asset to strengthen the surrounding tourism and economy in the future.

Healthier bay creates healthier ecosystem. The locals will be among the very firsts to experience the benefit of the healthy bay as many of them work in the water-related industry, such us water tourism and fishery.

One important approach to realizing a healtier and balanced bay is by reducing the bay sedimentation rate. In this thesis, all the possible sedimentation sources from surrounding land and water areas will be studied so that specific landscape strategies based on the area characteristics could be synthesized.

A BAY IN EQUIPOISE | A strategy to balance development and natural process in Benoa Bay, Bali

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GLOBAL BAY COMPARISON

Whittaker, Joanne, Alexey Goncharov, Simon Williams, R. Dietmar Müller, German Leitchenkov (2013) Global sediment thickness dataset updated for the Australian-Antarctic Southern Ocean, Geochemistry, Geophysics, Geosystems. DOI: 10.1002/ggge.20181 Bathymetry (GEBCO) | NASA. (2016). Bathymetry (GEBCO) | NASA. from http://neo.sci.gsfc.nasa.gov/view.php?datasetId=GEBCO_BATHY

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POSITIONING

CONTEXT

Survey, U. (2016). Landsat. Earthexplorer.usgs.gov. from http://earthexplorer.usgs.gov Hijmans, R., Guarino, L., & Jarvis, A. (2016). DIVA-GIS. Retrieved 13 June 2016, from http://www.diva-gis.org/gdata Metro Extracts · Mapzen. (2016). Mapzen.com. Retrieved 13 June 2016, from https://mapzen.com/data/metro-extracts/

Department of Marine and Fisheries Bali Provincial Government,. (2016). Benoa Bay Administration Area Map. Department of Marine and Fisheries Bali Provincial Government,. (2016). Benoa Bay Topography and Bathymetry.

Department of Marine and Fisheries Bali Provincial Government,. (2016). Benoa Bay Watersheds.

Department of Marine and Fisheries Bali Provincial Government,. (2016). Benoa Bay Coastal Ecosystems.

Benoa bay, located at the southern part of Bali, is a 1988.1 ha shallow water body. The Benoa Peninsula and Turtle Island frame the bay’s eastern edge. The bay’s waters connect to the Indian Ocean via the narrow bay mouth between Benoa Peninsula and Turtle Island. The bay is strategically located in the middle of the tourism-based economic growth areas. It actually can be seen as the main gate to Bali Island as it is surrounded by Ngurah Rai International Airport, Benoa Port, highway, and primary roads. The bay is an estuary for some rivers in South Bali; it has important functions to the ecosystem and community. It keeps ecological and hydrological stability as well as supports the economy and socio-culture of the Balinese. The bay is surrounded by very diverse ecosystems; mangroves, sea grass, and corals. All these ecosystems are essential as they work together to keep the balance of the bay.

A BAY IN EQUIPOISE | A strategy to balance development and natural process in Benoa Bay, Bali

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THE SIGNIFICANCE OF THE BAY

Ministry of Marine Affairs and Fisheries Republic of Indonesia,. (2016). Feasibility Study of Benoa Bay Revitalization Project. Jakarta.

Benoa is very important on both local and national scale because of its strategic location. The surrounding tourism industries affects local and national economy. Hence, a big amount of invesment is being poured by government and investors to develop this area. Many had ambitious development proposals for the bay, yet few of them are sustainable for the environment. The increasing rate of the bay sedimentation is one thing we need to overcome and to be considered in any masterplan for the bay. If the bay is healthier, it could function more effectively and better support surround local / tourism activities.

8

POSITIONING

PAST

These diagrams highlight the change of Benoa bay from 1989 to 2015. The bay & surrounding areas have experienced drastic change during this period. If we compare the bay sedimentation on 2015 with that on 1989, we can see that the bay sedimentation has increased significantly.

1989

Sedimentation is a natural process. Before large urbanisation happened, there had been natural sedimentation at the bay. There was less human intervention at that time. Many of the coastal edges inside the bay were sandy beaches; few parts were surrounded by mangroves. Turtle Island was still 111 ha and still separated from main Bali Island. Benoa Port just started its 1st stage of land reclamation.

1995

The start of large urbanisation. People started to develop the land and sea. Benoa Port continued the 2nd stage of land reclamation on 1990, followed by Turtle Island land reclamation on 1994. These land reclamation created severe coastal erosion that affected the whole inner bay. Government started to plant more mangroves to prevent further coastal erosion. However, not all areas can be easily planted with mangroves. There were only few mangroves successfully planted near Pudut Island, eastern part of the bay. The sedimentation was noticeably increased.

1997

Turtle Island land reclamation was 70% done. This reclamation made the bay mouth much more narrow than before. As a result, the water current near the bay mouth was much stronger than before. The coastal erosion was massive, especially around Pudut Island.

2002

Pudut Island was nearly gone because of the coastal erosion. Originally, it was 10 ha, yet, in 2002, it became only around 1 ha. In addition, the reclamations also blocked the nearby water flow; this affected in more sedimentation.

2015

On 2014, a highway above the bay water has been constructed. The construction left some materials, mostly lime stones, below the structures which also increased the bay sedimentation. An investor wanted to reclaim the whole bay and turn it into a tourism development. The project is now under feasibility study. Recently, Benoa bay has been changed from conservation zone into tourism development zone.

Survey, U. (2016). Landsat. Earthexplorer.usgs.gov. from http://earthexplorer.usgs.gov

A BAY IN EQUIPOISE | A strategy to balance development and natural process in Benoa Bay, Bali

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POSITIONING

A BAY IN EQUIPOISE | A strategy to balance development and natural process in Benoa Bay, Bali

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12

POSITIONING

A BAY IN EQUIPOISE | A strategy to balance development and natural process in Benoa Bay, Bali

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14

POSITIONING

NOW

Nowadays, the bay is imbalance as it encounters a lot of pressure. The sedimentation rate at the bay is so high that it is not effective for many water activities. This is a result of many factors, such us: increasing urbanisation, rapid development, agricultural practice, past land reclamations, highway construction, and the natural characteristic of the watershed itself. All these things can raise chances of soil erosion / coastal erosion / water flow blockage that result in the increase of bay sedimentation. This condition has terrible impact to both surrounding ecosystem and community.

A BAY IN EQUIPOISE | A strategy to balance development and natural process in Benoa Bay, Bali

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16

POSITIONING

A BAY IN EQUIPOISE | A strategy to balance development and natural process in Benoa Bay, Bali

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FUTURE

The future of Benoa bay may have 3 possible options: if we do nothing, if we follow investor’s proposal ( to reclaim the bay ) , and if we make effort to balance the bay. Not doing anything to tackle the sedimentation issue could lead to many environmental problems, while reclaiming the bay may even destroy bay ecosystem. Therefor, some landscape strategies need to be made to reduce the sedimentation rate at the bay.

If we do nothing

FUTURE

permanent lands

mangroves will die ( lack of water )

blocked waterways

fishery and water tourism will be threaten

destroyed habitat

mangroves, seagrass, and corals will die

blocked sunlight

seagrass will die, fishes have little food

If we follow current investor proposal

land reclamation

+ national economy - not sustainable, continues dredging along all built canals - creating new land by destroying another island - destroy ecosystem : mangroves - less local oriented

If we make effort to balance the bay

less sedimentation

healthier bay

healthier ecosystem

benefit the local

18

productive bay

improve local economy: tourism & fishery

POSITIONING

if we do nothing..

SEDIMENTATION | CREATING NEW LANDS The sedimentation is getting worse because of surrounding construction, development, and reclamations. People said that before in an area the sediment was only 10 cm thick, now it is 50 cm thick.

Then, many parts of the bay could become new lands in the future..

A BAY IN EQUIPOISE | A strategy to balance development and natural process in Benoa Bay, Bali

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if we do nothing..

BLOCKED WATERWAYS As the bay is semidiurnal, it has 2 high tides and low tides a day. The bay water is only effective for fishing and other water activities for 4 hours a day. During low tides, the boats cannot move because of the sediments. The effective areas for water tourism and fishermen are getting smaller day by day. In the future, there will be less water tourism and fishery inside the bay.

20

POSITIONING

if we do nothing..

DESTROYED HABITAT More mangroves will die because of lack of water as some waterways are blocked by sediments. It is hard for the seawater to reach the mangroves. The sediments also cover the mangrove’s roots, making them dying. The mangroves here have significant role: to prevent coastal erosion and filter the water. In the future, the mangroves, corals, and sea grass could all be disappeared.

A BAY IN EQUIPOISE | A strategy to balance development and natural process in Benoa Bay, Bali

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if we do nothing..

BLOCKED SUNLIGHT The sediments also block the sunlight. This, in fact, affects the sea grass. If there is no sea grass, there will be less food for the sea biota.

The number of fishes, shrimps, and seashells will decrease and the fishermen need to change their jobs.

22

POSITIONING

if we reclaim the bay..

DESTROYED ECOSYSTEM IN THE MATERIAL SOURCE AREA

LONG-TERM COMMITMENT

The process of taking material for reclamation from the sea may seriously affect the water ecosystem there. This will also influence the surrounding locals who depend their lives on it.

The fact that the entire water canals require to be dredged periodically is a big long-term commitment for the government and investor. The high cost and effort of dredging makes it as not a very sustainable option.

A BAY IN EQUIPOISE | A strategy to balance development and natural process in Benoa Bay, Bali

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RESEARCH & DESIGN METHODOLOGY & PROPOSED PROJECT BRIEF

The following keywords and sentences are reference words for the process of thesis research and design. The process can go either sequential or back and forth.

24

SPECULATION

26

SITE VISIT

SPECULATION

POPULATION STUDY

Benoa Port

fishermen village

Benoa Port

water tourism

fishermen village

water tourism

Ministry of Marine Affairs and Fisheries Republic of Indonesia,. (2016). Feasibility Study of Benoa Bay Revitalization Project. Jakarta.

There are about 100.000 people live surround the bay. Most of them are locals who are working in agricultural, tourism/trading, or fishery industry. Badung and Mati Watershed have the most dense population and most are working in tourism and agricultural field. Bualu Watershed is dominated by those working in water tourism and fishery industry. Sama Watershed is mostly bareland; parts of it have been developed into tourism and residential areas. There are some fishermen village located in Turtle Island and Benoa Peninsula.

A BAY IN EQUIPOISE | A strategy to balance development and natural process in Benoa Bay, Bali

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BAY DATA VISUALISATION

BENOA BAY WATER QUALITY The table shows that the level of suspended material in Benoa bay water is already too high.

Based on the environmental quality standard, it should be less than 20, while the bay’s is 116.20.

BENOA BAY TIDAL LEVEL The diagram shows the bay is semidiurnal. It has 2 low and high tides everyday. The flood and ebb time of the water vary everyday. The highest tide (Highest Astronomical Tide) is + 2.95m yet the lowest is +0.22m.

28

Ministry of Marine Affairs and Fisheries Republic of Indonesia. (2016) Feaibility Study of Benoa Bay Revitalization Project. http://www.indosurf.com.au, P. (2016). Bali Tide Charts 2016 & 2017 - exclusive to Indo Surf ‘n Lingo, The #1 Bali Surfing Guidebook. Indosurf.com.au. Retrieved 10 June 2016, from http://www.indosurf.com.au/tide_charts.html

SPECULATION

TOTAL SUSPENDED MATERIAL Based on the total suspended material diagram, The waterbody at eastern part of the bay ( near Turtle Island and Pudut Island ) has the highest suspended material. Other areas that have high sedimentation are areas near Mati River delta and Sama River delta.

TIDAL RESIDUAL CURRENT The area near Pudut Island has high tidal residual current.

However, the sedimentation level there is also high. This may because of the coastal erosion.

The strong water current erodes Pudut island. The northern part of the bay tend to have low residual current as it is blocked by Benoa Port and Turtle Island.

Hendrawan, I. & Asai, K. (2014). Numerical study on tidal currents and seawater exchange in the Benoa Bay, Bali, Indonesia. Acta Oceanologica Sinica, 33(3), 90-100. http://dx.doi.org/10.1007/s13131-014-0434-5 Komang, A. & Mahendra, S. (2014).Study of Pollutant Distribution in Benoa Bay Using Numerical Simulation and Satellite Data. from http://ojs.unud.ac.id/index.php/ECOTROPHIC/article/view/250

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10

9

AVERAGE TIDAL HEIGHT

4

year 2015 year 2012 year 2009

3

2

5

4

3

5

5

2

6

6

1 6

0

500

1000

1500

mm 2000

0

°C 10 20 30 40 0

7

11

11 9

8

30

7

7

12

8

The diagram represents the average water level at Benoa bay.

March usually has the highest whilst August has the lowest.

°C 10 20 30 40

12

7

9

6

1

10

AVERAGE AIR TEMPERATURE ( °C ) AVERAGE SEA TEMPERATURE ( °C )

10

AVERAGE TIDAL HEIGHT

http://www.indosurf.com.au, P. (2016). Bali Tide Charts 2016 & 2017 - exclusive to Indo Surf ‘n Lingo, The #1 Bali Surfing Guidebook. Indosurf.com.au. Retrieved 10 June 2016, from http://www.indosurf.com.au/tide_charts.html

year 2015

8

10

AVERAGE RAINFALL ( mm ) AVERAGE RAINY DAYS

AVERAGE TIDAL HEIGHT year 2015 year 2012 4 year 2009

4

2

5

3

3

4

3

2

5

2

SPECULATION

9

10

9

2

5

N NNW

NNE

NW

NE

6

1

1

6

1

6

1 WNW

0

500

1000

mm 2000

1500

0

°C 10 20 30 40 0

°C 10 20 30 40

W

0

5

ENE

days 10 15 20 0

25

50

75

100

E

mm 125

0

WSW

7

12

0

kts 10 20

ESE

7

12

7

12

% 10 20 30 40

12

SW

SSW

SE

SSE S

11

8

11

9

The diagrams represent the average rainfall ( outer circle ) and and number of rainy days ( inner circle ) at Benoa bay. January is the wettest month while July and August are the driest months.TIDAL HEIGHT AVERAGE

year 2015

911

8 10

AVERAGE AIR TEMPERATURE ( °C ) 9 AVERAGE SEA TEMPERATURE ( °C )

(2016). from https://weather-and-climate.com/average-monthly-Rainfall-Temperature-Sunshine,tanjung-benoa,Indonesia

11

8

10

WIND SPEED ( kts ) WIND PROBABILITY ( % ) WIND DIRECTION

10

AVERAGE RAINFALL ( mm ) AVERAGE RAINY DAYS

A BAY IN EQUIPOISE | A strategy to balance development and natural process in Benoa Bay, Bali

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year 2015 year 2012 year 2009

9

10

AVERAGE AIR TEMPERATURE ( °C ) AVERAGE SEA TEMPERATURE ( °C ) 4

3

5

2

5

N

6

1

6 WNW

0

C °C 10 20 30 40 0

W

°C 10 20 30 40

WSW

7

12

7

S

11

8

9

The diagrams represent the air ( outer circle ) & water ( inner circle ) temperature at Benoa bay.

January is the hottest month and July is the coolest month.

32

(2016). from https://weather-and-climate.com/average-monthly-Rainfall-Temperature-Sunshine,tanjung-benoa,Indonesia

10

AVERAGE AIR TEMPERATURE ( °C ) AVERAGE SEA TEMPERATURE ( °C )

8

AVERAGE RAINY DAYS 9

10

9

10

WIND SPEED ( kts ) WIND PROBABILITY ( % ) WIND DIRECTION

AVERAGE AIR TEMPERATURE ( °C ) AVERAGE SEA TEMPERATURE ( °C ) 4

2

3

SPECULATION

year 2015 year 2012 year 2009

2

5

N NNW

NNE

NW

1

NE

6

1 WNW

0

°C 10 20 30 40 0

°C 10 20 30 40

ENE

W

E 0

WSW

12

% 10 20 30 40

0

kts 10 20

ESE

7

12

SW

SE

SSW

SSE S

11

The diagram represents the wind characteristics at Benoa bay. The The major wind direction is from East-southeast direction. The highest wind probability is on July and the fastest wind is usually on December.

GE AIR TEMPERATURE ( °C ) GE SEA TEMPERATURE ( °C )

11

8

9

(2016). from https://weather-and-climate.com/average-monthly-Rainfall-Temperature-Sunshine,tanjung-benoa,Indonesia

10

WIND SPEED ( kts ) WIND PROBABILITY ( % ) A BAY IN EQUIPOISE | A strategy to balance development and natural process in Benoa Bay, Bali

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TIDAL LEVEL STUDY MODELS

mean low water spring +0.23

34

mean sea level +1.30

mean high water spring +2.41

SPECULATION

SITE SELECTION METHODOLOGY

Mati Watershed

Mati river delta

Sama river delta

Turtle Island

Pudut Island

Bualu Watershed

Sama Watershed

From the total suspended matter and tidal residual current diagrams, we can know which parts of the bay have severe sedimentation. The highest sedimentation is usually located either near the river delta or other sediment sources such us material deposition, water flow blockage, and coastal erosion. There are mainly 4 areas at the bay that have very high sedimentation; the northern part that is near Mati & Badung river delta, the western part of Turtle island, surround Pudut Island, and near Sama river delta. The next step was to study the watersheds that end / related to these bay area. This study includes soil erosion analysis, land use, soil type analysis, river speed, and sediment amount calculation.

By studying the surrounding watersheds and comparing it to the bay sedimentation and tidal characteristic, 4 specific sites from 4 different watersheds have been chosen for further design development. The chosen sites are either directly at the bay water or upland, which depend on the characteristic of the watersheds and will be explained in the next pages.

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name

bay sedimentation

sedimentation source

does the existing already have solution?

urgency ( chosen site )

1. BADUNG

high

2. MATI

high

soil erosion

no

medium

coastal erosion

no

4. SAMA

high

waterflow blockage

no

yes

5. BUALU

very high

material deposition

no

yes

6. TURTLE ISLAND

very high

no

yes

3. TUBAN

yes

yes

6 WATERSHEDS

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SPECULATION

GENERAL STRATEGY

Possible sedimentation sources from both surrounding land and water areas were studied so that specific landscape strategies based on the area characteristics could be synthesized.

BADUNG RIVER WATERSHED ( 5582 Ha )

MATI RIVER WATERSHED ( 3409 Ha )

H RAI

MANGROVE

BY

PASS

NGURA

high bay sedimentation because of urbanisation and agricultural practice in the watershed 35

TURTLE ISLAND

MATI RIVER DELTA BADUNG ESTURAY DAM

COMMERCIAL AREA

MANGROVE CENTER

SITE 1

LOCAL WATER COMPANY

PERENNIAL RIVER DELTA

MANGROVE

10

TURTLE ISLAND

SITE 4

ECO PARK

CORAL REEF

UNFINISHED LAND RECLAMATION

BENOA PORT

CUT SLOW

UNFINISHED RECLAMATION ( ABANDONED )

10

TUBAN WATERSHED ( 798 Ha )

NATURAL FLOW SEVERE SEDIMENTATION

11

3

15

11

2

15

SITE 3

PUDUT ISLAND

PUDUT ISLAND

FISHERMEN VILLAGE

3

20

5

15

RY

AIRPORT

high bay sedimentation because of material deposition from past reclamation and waterflow blockage as a result of narrowing the channel

5

BO

CORAL REEF

RT

2 SEAGRASS

PO

BENOA PENINSULA

UN

DA

MANGROVE

high bay sedimentation because of eroded material from coastal erosion

30

30

SITE 2

INTERMITTEN RIVER

BY PASS NGURAH RAI

SEAGRASS

SAMA RIVER DELTA

LOCAL VILLAGE

40

high bay sedimentation because of suddenSAMA water movement RIVER during rainy season & WATERSHED ( 2390 Ha ) easily eroded soil type in the watershed

GENERAL STRATEGY TO BALANCE THE BAY : 50 BUALU RIVER WATERSHED ( 961 Ha )

NUSA DUA

1. CREATE SEDIMENT CATCHMENT & STRATEGICALLY DREDGE ON CRUCIAL DELTA POINTS 2. REDUCE SOIL EROSION FROM UPHILL 3. REDUCE COASTAL EROSION AROUND BAY MOUTH 4. WIDEN THE BAY MOUTH TO SLOW DOWN THE WATER

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MATI WATERSHED | RESEARCH Mati River is a natural permanent river that is located in the busy urban & commercial area in Kuta. This area has been developed very much compare to that in the past. However, there are not many people that have direct contact and use with this river. Many even built walls as boundaries between the river and their properties. The surrounding developments contribute much to the imbalance state of the bay right now.

Mati River runs in the southern low land of Bali; it ends at the mangrove area at the edge of the bay. The river speed is 8899m3/s, which even double the speed of the biggest river around Benoa, Badung River. This river brings a lot of sediments, mostly from the soil erosion at surrounding agricultural and urban area. The sediments here are rich in nutrients as the surrounding soil is mostly Ochric Andosols, which is very fertile because from a volcanic activity. Based on USLE calculation, it is predicted that there will be 103m3 soil eroded here everyday. This will add 10m3 of sand, 9m3 of silt, and 6.37m3 of clay into the delta everyday. In a year, this could cover a regulation sized soccer field 1m thick. That’s why we have a high rate of sedimentation around the nearby water edge here.

As the site is located in a river delta that brings a huge amount of water and sediments everyday, it is necessary that the design proposed here can filter the sediments without blocking the water flow. Annual dredging is also necessary to bring out the accumulated sediments, which later can be used to benefit surrounding people.

SITE CHARACTERISTIC

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SITE

SPECULATION

MATI WATERSHED | DESIGN TACTICS : strategic dredging

1 year 1amount of sediments year amount of sediments +/- 37345 = +/-=37345 M3m3

TOBE BE TO DREDGED DREDGED

SWEEPING DEVICE

SWEEPING DEVICE annual, automatic annual, automatic

CATCHMENT POND

The yearly amount of sediment from Mati watershed was calculated to know how big the sediment basin should be. The result was 37345 m3 which most are gravels. One year period was chosen considering the basin volume needed and the dredging cost. A moving device will be installed at the basin to clean the sediment. Because the size of gravel is not so small, it is possible to capture and sweep it by this device. Every year, the device will sweep the sediment from sediment basin to the catchment so that it can be easily dredged. The strategic dredging idea offers efficiency in dredging, as it will only happen at the catchment pond, not the whole basin. The basin was designed to be wider at the part that is closer to the bay so that the sediment and water flow can be directed more to the bay.

A BAY IN EQUIPOISE | A strategy to balance development and natural process in Benoa Bay, Bali

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MATI WATERSHED | DESIGN

ESTUARY

URAH

SS NG

BY PA RAI

MANGROVE

40

SPECULATION

MATI WATERSHED | DESIGN

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SPECULATION

SAMA WATERSHED | RESEARCH

Sama watershed is located at the south west part of the bay.

The river here is intermitten; the water is usually just stagnant during dry season. The surrounding soil is mostly Lithosols, a thin soil layer consists of partially weathered rock fragments.

This kind of soil lacks of nutrients; it is not fertile like Mati’s that it needs planting to make it more fertile. About 80% of the watershed area are still bare lands. The watershed has some hills in the southern area. Most of its urban area is located in the low land.

Although there is not much river flow during dry season, the sedimentation at the edge of the bay water is also high. The river brings most of the sediments during the wet season. It is calculated that in average, the river brings about 32m3 of sediments a day to the bay. It contains 5m3 of sands, 1.3m3 of silt, and 0.24m3 of clay a day. The particles size are generally bigger than those in Mati’s as they are from rocky areas.

Though the daily amount is also not as big as Mati’s, in a year, this will be like a quarter of regulation sized soccer field in 1m thickness.

There is a high soil erosion risk in this watershed. In the beginning of rainy season, there will be sudden water movement that brings a lot of sediment from uphill. As the soil type here is very easy to be eroded, the landscape strategy to reduce sedimentation for this watershed will be more appropriate on the uphill, more specifically, on the steep slope that has high soil erosion risk. Therefor, the strategy to prevent the sediments here from entering the bay is to create natural barriers.

SITE SITE CHARACTERISTIC

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SAMA WATERSHED | DESIGN TACTICS : Living Barrier

Living barrier is actually a planting strategy; it has 2 major ideas: Firstly, plant a mixed plantation along the contour line. There will be different proportion of yearly trees and seasonal trees according to the slope gradient. The steeper the slopes are, the more yearly trees should be planted. Some trees that are suitable for the site context are Teak, Mahogany, Sonokeling, Sandalwood, Mango, Durian, Petai, Candlenut, and Melinjo. Secondly, we can plant Vetiver grass along the contour lines in the steep slopes. The steeper the slopes are, the denser the grass should be. For area that has gradient more than 25%, it is necessary to add a ditch after the grass to help to slow down the water during rainy season.

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SPECULATION

SAMA WATERSHED | DESIGN

GO

AG

ON

G

GWK CULTURAL PARK

A BAY IN EQUIPOISE | A strategy to balance development and natural process in Benoa Bay, Bali

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46

SAMA WATERSHED | DESIGN

SPECULATION

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BUALU WATERSHED | RESEARCH Bualu watershed stretchs from the east to the south of Benoa bay.

The eastern part of bualu is a peninsula. This peninsula has a high risk of coastal erosion which was even more severe since we had Turtle Island reclamation as it changed the water current and strength drastically. The water current became stronger at the bay mouth as it got narrower. There is not much soil erosion here as the peninsula is almost flat; in average, there is only 6.5m3 of sediments a day from surface runoff going into the bay. The surrounding soil is a mix of fertile soil ( Eutric Regosols ) and barren soil ( Lithosols ).

The bay sedimentation here is also very high, mostly coming from the past coastal erosion.The sediment type here is clayey sand with gravel. Not far from the coastal edge, there is Pudut island. This island experienced severe coastal erosion that it lost 90% of its original area.

Now, the island is only about 1 ha. It is hard for mangrove to grow here as they have built concrete and rock wall along the coastal edge to prevent further coastal erosion.

The water area around the island is actually very shallow but it is still hard to see until the sea bed because of sedimentation. We have many corals along the east side of the peninsula and seagrass around the Pudut island. The local who lives around here are usually more engaged to the water; many of them are working in water sport, turtle conservation, & fishery. Those people depend their lives on the bay water, habitat, and ecosystem.

It is important to create a coastal protection for Pudut Island so that it won’t be eroded anymore in the future. In addition, we can also use the sedimentation problem as an opportunity to restore the Island to its original size, then the space can be used for habitat enhancement, aquaculture, or eco tourism.

SITE CHARACTERISTIC

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SITE

SPECULATION

BUALU WATERSHED | DESIGN TACTICS : Coastal Protection and Island Restoration

Pudut Island

Pudut Island

A coastal protection for Pudut island is needed so that it won’t be severly eroded anymore in the future. As there is a strong tidal current that erodes the land at the western side of Pudut island, the strategy here is to build breakwaters. There can be two stripes of breakwater; one is to protect the island from the highest tide, another from the high water spring. The area between these breakwaters will be filled with calmer water. This area provides opportunity for habitat growth such us sea grass and mangroves as well as eco tourism and fishing. As the area in between still has water, the fishermen and tourism boats can go through it. For the breakwater material, we can use tetrapod as it is easy to be constructed and has many gaps between every piece. The gap will be filled with water and can be the habitat for small fishes.

Another idea here is to restore this island to be close to its original size in the past. The design is similar to that in the western side; the difference is just the tetrapod should be pilled up to mean low water. As the water comes in, it brings some sediment. This sediment will be trapped in the space, build up over time, and extend the island. This idea can be repeated several phases until we reach the desired area for the island restoration.

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BUALU WATERSHED | DESIGN

SPECULATION

BUALU WATERSHED | DESIGN

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SPECULATION

TURTLE ISLAND | RESEARCH

Turtle Island was reclaimed in 1995. The land reclamation was paused on 1998 when it was 70% done. The reclamation was built on the top of reef flat. This reclamation changed a lot of surrounding coastal ecosystem.

Firstly, as the bay mouth got narrowed, the tidal current became stronger that it made huge coastal erosion problem to surrounding sites. At that time, the whole inner bay edge was mostly sandy beach with mangroves in few locations. However, because of this coastal erosion, government and the locals started to plant more mangroves surround the bay edges.

Secondly, the land reclamation also narrowed the gap between the island and Benoa port that it resulted in the increase of total suspended material along the gap. The water from the top of Turtle Island cannot flow smoothly and the sediments are trapped between this gap.

Third, the land reclamation destroyed existing habitats, especially coral reef and seagrass. The soil type in the reclaimed area is mostly Calcaric Fluvisols, which is not a fertile soil. It has low pH and high salinity. The soil in the original land is Eutric Regosols. It is fertile but can be easily eroded.

Therefor, here, it is necessary to widen the bay mouth by removing some of the reclamation stonewalls. By widening the bay mouth, we can solve many problems at the same time. The water area inside the past walls could be a very unique environment because of the partly enclosed condition which could promote the growth of habitat.

SITE

SITE CHARACTERISTIC

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TURTLE ISLAND | DESIGN TACTICS : Sediment Flushing

Turtle Island reclamation has terrible impact to the surrounding areas; it narrowed the bay mouth, changed the tidal current, and blocked water flow. As the land reclamation near Benoa bay mouth is still not done, we can simply cut the seawalls to let water comes in and flushes the sediment at the western part of the island. There is a high sedimentation there as the reclaimed land block the water flow. By cutting these seawalls, we can also reduce the tidal force and minimize surrounding coastal erosion.

As cutting seawalls also can be a hard work, we can have 2 kinds of cutting; first, just cut a little that it is enough to let water comes in. Second, cut the whole of the walls, especially on the area that has high sedimentation so we can flush it out. The area inside those walls will have unique habitat characteristic as it is half-enclosed and occupied by some sea grass and corals. In the future, this can be developed more to be an interesting tourism destination.

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SPECULATION

TURTLE ISLAND | DESIGN

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TURTLE ISLAND | DESIGN

LITTLE CUT SEAWALLS

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100 % DEMOLISHED SEAWALLS

PARTLY ENCLOSED ENVIRONMENT

SPECULATION

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APPENDIXES

APPENDIXES

A STRATEGY TO BALANCE DEVELOPMENT AND NATURAL PROCESS IN BENOA BAY, BALI Benoa is a shallow intertidal bay located at the southern part of Bali, Indonesia, on the seashore of Indian Ocean. Besides its strategic location, the bay has a rich ecosystem and is a place for diverse activities and infrastructures. It has recently been a subject undergoing intense study in Indonesia because of its high environmental problems and social conflicts. Current bay condition shows the imbalance state of development and natural process. Researches showed a huge increase rate of sedimentation at the bay. The bay sedimentation is already too much right now that the bay is not effective for many activities. Most of the severe bay sedimentation is a result of surrounding human interventions that underestimate the importance of preserving the nature. If this continues, the surrounding ecosystem, community, and economy could be terribly affected. More mangroves, sea grass, and corals would die; locals would lose their jobs; water tourism would also be gone. I believe that now it is crucial to think of how to balance the bay in order to maintain the environmental sustainability. Development should be focused not only on accelerating the economic growth but more importantly also on environmental sustainability in which human can get the benefits in the long term. This proposal offers some strategies to create a healthier and more balanced bay that can be a valuable asset to strengthen the surrounding tourism and economy in the future. Healthier bay creates healthier ecosystem. The locals will be among the very firsts to experience the benefit of the healthy bay as many of them work in the water-related industry, such us water tourism and fishery. One important approach to realizing a healtier and balanced bay is by reducing the bay sedimentation rate. In this thesis, all the possible sedimentation sources from surrounding land and water areas will be studied so that specific landscape strategies based on the area characteristics could be synthesized.

GLOBAL CASE STUDY

THE SIGNIFICANCE OF THE BAY

IF WE DO NOTHING

SEDIMENTATION | CREATING NEW LANDS

GENERAL STRATEGY

BADUNG RIVER WATERSHED ( 5582 Ha )

MATI RIVER WATERSHED ( 3409 Ha )

SEDIMENTATION | BLOCKING WATERWAY

THE SEDIMENTATION IS GETTING WORSE BECAUSE OF SURROUNDING CONSTRUCTION, DEVELOPMENT, AND RECLAMATIONS. PEOPLE SAID THAT BEFORE IN AN AREA THE SEDIMENT WAS ONLY 10 CM THICK, NOW IT IS 50 CM THICK. THEN, MANY PARTS OF THE BAY COULD BECOME NEW LANDS IN THE FUTURE..

NGURAH

RAI

high bay sedimentation because of urbanisation and agricultural practice in the watershed

BY

PASS

MANGROVE

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TURTLE ISLAND

MATI RIVER DELTA BADUNG ESTURAY DAM

AS THE BAY IS SEMIDIURNAL, IT HAS 2 HIGH TIDES AND LOW TIDES A DAY. THE BAY WATER IS ONLY EFFECTIVE FOR FISHING AND OTHER WATER ACTIVITIES FOR 4 HOURS A DAY. DURING LOW TIDES, THE BOATS CANNOT MOVE BECAUSE OF THE SEDIMENTS. THE EFFECTIVE AREAS FOR WATER TOURISM AND FISHERMEN ARE GETTING SMALLER DAY BY DAY. IN THE FUTURE, THERE WILL BE LESS WATER TOURISM AND FISHERY INSIDE THE BAY.

COMMERCIAL AREA

MANGROVE CENTER

SITE 1

LOCAL WATER COMPANY

PERENNIAL RIVER DELTA

MANGROVE

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SEDIMENTATION | DESTROYING HABITAT

TURTLE ISLAND

SITE 4

ECO PARK

CORAL REEF

UNFINISHED LAND RECLAMATION

BENOA PORT

CUT TUBAN WATERSHED ( 798 Ha )

NATURAL FLOW

MORE MANGROVES WILL DIE BECAUSE OF LACK OF WATER AS SOME WATERWAYS ARE BLOCKED BY SEDIMENTS. IT IS HARD FOR THE SEAWATER TO REACH THE MANGROVES. THE SEDIMENTS ALSO COVER THE MANGROVE’S ROOTS, MAKING THEM DYING. THE MANGROVES HERE HAVE SIGNIFICANT ROLE: TO PREVENT COASTAL EROSION AND FILTER THE WATER. IN THE FUTURE, THE MANGROVES, CORALS, AND SEA GRASS COULD ALL BE DISAPPEARED.

SLOW

SEDIMENTATION | BLOCKING SUNLIGHT

SEVERE SEDIMENTATION

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3

15

11

2

15

SITE 3

PUDUT ISLAND

PUDUT ISLAND

FISHERMEN VILLAGE

3

20

5

15 RY

AIRPORT

high bay sedimentation because of material deposition from past reclamation and waterflow blockage as a result of narrowing the channel

5

UNFINISHED RECLAMATION ( ABANDONED )

10

BO

CORAL REEF

SEAGRASS

PO

BENOA PENINSULA

RT

2

UN

DA

MANGROVE

high bay sedimentation because of eroded material from coastal erosion

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30

SITE 2

INTERMITTEN RIVER

THE SEDIMENTS ALSO BLOCK THE SUNLIGHT. THIS, IN FACT, AFFECTS THE SEA GRASS. IF THERE IS NO SEA GRASS, THERE WILL BE LESS FOOD FOR THE SEA BIOTA. THE NUMBER OF FISHES, SHRIMPS, AND SEASHELLS WILL DECREASE AND THE FISHERMEN NEED TO CHANGE THEIR JOBS.

DESTROYED ECOSYSTEM IN THE MATERIAL SOURCE AREA

SEAGRASS

BY PASS NGURAH RAI

IF WE RECLAIM THE BAY

SAMA RIVER DELTA

LONG-TERM COMMITMENT

LOCAL VILLAGE

THE PROCESS OF TAKING MATERIAL FOR RECLAMATION FROM THE SEA MAY SERIOUSLY AFFECT THE WATER ECOSYSTEM THERE. THIS WILL ALSO INFLUENCE THE SURROUNDING LOCALS WHO DEPEND THEIR LIVES ON IT.

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high bay sedimentation because of suddenSAMA water movement RIVER during rainy season & WATERSHED ( 2390 Ha ) easily eroded soil type in the watershed THE FACT THAT THE ENTIRE WATER CANALS REQUIRE TO BE DREDGED PERIODICALLY IS A BIG LONG-TERM COMMITMENT FOR THE GOVERNMENT AND INVESTOR. THE HIGH COST AND EFFORT OF DREDGING MAKES IT AS NOT A VERY SUSTAINABLE OPTION.

GENERAL STRATEGY TO BALANCE THE BAY : 50 BUALU RIVER WATERSHED ( 961 Ha )

NUSA DUA

1. CREATE SEDIMENT CATCHMENT & STRATEGICALLY DREDGE ON CRUCIAL DELTA POINTS 2. REDUCE SOIL EROSION FROM UPHILL 3. REDUCE COASTAL EROSION AROUND BAY MOUTH 4. WIDEN THE BAY MOUTH TO SLOW DOWN THE WATER

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BIBLIOGRAPHY

DATA | aerial images, mapping, baseline drawings, statistics, diagrams Hijmans, R., Guarino, L., & Jarvis, A. (2016). DIVA-GIS. Retrieved 13 June 2016, from http://www.diva-gis.org/gdata Metro Extracts · Mapzen. (2016). Mapzen.com. Retrieved 13 June 2016, from https://mapzen.com/data/metro-extracts/ Survey, U. (2016). STRM 1 Arc-Second Global. Earthexplorer.usgs.gov. Retrieved 13 June 2016, from http://earthexplorer.usgs.gov Survey, U. (2016). Landsat. Earthexplorer.usgs.gov. from http://earthexplorer.usgs.gov Hendrawan, I. & Asai, K. (2014). Numerical study on tidal currents and seawater exchange in the Benoa Bay, Bali, Indonesia. Acta Oceanologica Sinica, 33(3), 90-100. http://dx.doi.org/10.1007/s13131-014-0434-5 http://www.indosurf.com.au, P. (2016). Bali Tide Charts 2016 & 2017 - exclusive to Indo Surf ‘n Lingo, The #1 Bali Surfing Guidebook. Indosurf.com.au. Retrieved 10 June 2016, from http://www.indosurf.com.au/tide_charts. html (2016). from https://weather-and-climate.com/average-monthly-Rainfall-Temperature-Sunshine,tanjung-benoa,Indonesia Ministry of Marine Affairs and Fisheries Republic of Indonesia,. (2016). Feasibility Study of Benoa Bay Revitalization Project. Jakarta.

Komang, A. & Mahendra, S. (2014).Study of Pollutant Distribution in Benoa Bay Using Numerical Simulation and Satellite Data. from http://ojs.unud.ac.id/index.php/ECOTROPHIC/article/view/2500 Google Earth (2014). Satellite imagery. Benoa.

Bathymetry (GEBCO) | NASA. (2016). Bathymetry (GEBCO) | NASA. from http://neo.sci.gsfc.nasa.gov/view.php?datasetId=GEBCO_BATHY Gridded bathymetry data (General Bathymetric Chart of the Oceans).. (2016). GEBCO. Retrieved 13 June 2016, from http://www.gebco.net/data_and_products/gridded_bathymetry_data/ Whittaker, Joanne, Alexey Goncharov, Simon Williams, R. Dietmar Müller, German Leitchenkov (2013) Global sediment thickness dataset updated for the Australian-Antarctic Southern Ocean, Geochemistry, Geophysics, Geosystems. DOI: 10.1002/ggge.20181 Department of Marine Affairs and Fisheries Bali Provincial Government,. (2016). Benoa Bay Administration Area.

Department of Marine Affairs and Fisheries Bali Provincial Government,. (2016). Benoa Bay Topography and Bathymetry.

Department of Marine Affairs and Fisheries Bali Provincial Government,. (2016). Benoa Bay Watersheds.

Department of Marine Affairs and Fisheries Bali Provincial Government,. (2016). Benoa Bay Coastal Ecosystems.

Department of Marine Affairs and Fisheries Bali Provincial Government,. (2016). Benoa Bay Geological Structure.

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ACKNOWLEDGEMENT

I firstly want to thank God for His wonderful providence.

I would also like to thank my thesis supervisor, Mr. Scott Jennings Melbourne for his kind guidance, motivation, teaching, and patience throughout the thesis process. He gave me many valuable suggestions and ideas that inspired me alot. Though my projects are still far from perfect, I am really grateful of the learning process; knowing that my passion, understanding, and ability in landscape architecture have improved much more under his guidance.

I want to express deepest appreciation to Mr. Matthew Pryor, Mr. Ivan Valin, Mr. Ashley Scott Kelly, Ms. Dorothy Tang, Ms. Vincci Mak, Mr. Gavin Coates, and Mr. Andrea Palmioli for their time and valuable comments on my thesis project.

I would like to acknowledge those who helped me during the site visit and data collection in Bali: Mr. I Made Sudarsana from Department of Marine Affairs and Fisheries Bali Provincial Government, Mr. Gede Suarjana from Department of Environment Bali Provincial Government, and Mr. Jaelani from Indonesian Ministry of Marine Affairs and Fisheries.

I would like to thank all staff in the Faculty of Architecture in the University of Hong Kong whose technical supports are appreciated.

I feel so blessed and thankful to have uncountable support, care, and encouragement from my dearest family and friends throughout the thesis journey.

To all who, directly or indirectly, have lent their helping hand in this thesis project, I place my sense of gratitude.

This thesis would not have been possible without the support from all of you.

Thank you!

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STATEMENT OF ACADEMIC INTEGRITY

I declare that this thesis represents my own work, except where due acknowledgement has been made, and that it has not been previously been included in a thesis, dissertation or report submitted to this University or to any other institution for a degree, diploma or other qualifications.

LAURA RULIANTO signed name :

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