Advances in Tropical Biodiversity and

Environmental Sciences

6(3): 72-78, October, 2022

e-ISSN:2622-0628

DOI: 10.24843/ATBES.2022.v06.i03.p02

Available online at: https://ojs.unud.ac.id/index.php/ATBES/article/view/90081

Planning of Vegetative Structures for Coastal Protection based on Analysis of the Results of Coastal Substrate in Palu Bay

Suprabadevi Ayumayasari Saraswati1*, Watiniasih2, Arie Setiadi Moerwanto3 and Husnayaen4

1Study Program of Aquatic Resource Management, Faculty of Marine Animal Husbandry and Fisheries, Nusa Cendana University

2Marine Science Department, Marine Science and Fisheries Faculty, Udayana University 3Minister For Public Works and Human Settlements,Jakarta-Indonesia

4Environmental Engineering Study Program, Bali Nahdlatul Ulama Institute of Science and Technology, Bali-Indonesia Coressponding author: [email protected]

Abstract. An earthquake followed by a tsunami occurred on September 28, 2018 in Central Sulawesi. [8] recorded that 2.113 people died from the earthquake and tsunami, spread over 1.703 people in Palu City, 171 people in Donggala Regency, 223 people in Sigi Regency, 15 people in Parigi Moutong Regency, and Pairskayu Regency with a total of 15 people. 1 person. According to satellite imagery data obtained [2], damage to buildings that occurred in Palu City reached 2.403 buildings and caused the paralysis of Palu City from various aspects, around 70,000 people were accommodated in temporary shelters. Structural mitigation efforts to reduce the impact of damage from natural disasters can be done naturally or artificially. One of the natural structural mitigation efforts in the coastal area of Palu City is the creation of a coastal green belt or generally called a Greenbelt. Planting coastal vegetation and mangroves and maintaining existing coastal forest ecosystems is a disaster mitigation effort. Coastal forest ecosystems and mangroves have strong and sturdy root systems that can grip to the deepest soil layers. The canopy is flat and dense, and dense at all times, making coastal forests and mangroves an ideal natural protection against the threat of disasters in coastal areas. The purpose of this research is to plan the formation of coastal forest (Planning Vegetative Structure for Coastal Protection) in Palu City Bay. The method used in this research is descriptive method, namely by field observation, which is carried out to determine the existing condition of vegetation in the coastal area of Palu Bay.Based on the results of the analysis, at 23 measurement points, it was found that the thickness of the fine sediment at the bottom of the water ranged from 1-10 cm, while the results of the analysis of the thickness of the coarse sediment ranged from 1-26 cm. The sediment population in Palu City has the characteristics of Gravel (gravel) and Sand (sand). The potential content of TSS in the water column reaches 188 mg/l.

Keywords. Sediment, Vegetation, Community Development, Palu

  • I.    INTRODUCTION

Indonesia is an archipelagic country with a very wide coastal area and has abundant natural resources, also has a very high potential for natural disasters such as earthquakes, tsunamis, tidal waves, floods, abrasion, accretion, sea water intrusion and strong winds. All of these natural disasters threaten the people who live and depend on the coast and have a bad impact on other coastal ecosystems. [7] Structural mitigation efforts to reduce the impact of damage from natural disasters can be done naturally or artificially. One of the natural structural mitigation efforts in coastal areas, especially beaches, is the creation of a coastal green belt or generally called a Greenbelt. The manufacture and rehabilitation of structural

mitigation efforts naturally in the form of Greenbelt has several advantages, namely the manufacture tends to be more economical, has various environmental services and has ecological functions for the surrounding ecosystem.

Palu Bay is a bay in the waters of Central Sulawesi with a coastline of approximately 47 km whose existence is very important, both for residents living on the coast to those living in urban areas. This coastal area along Palu Bay is included in the administrative area of Palu City and Donggala Regency, Central Sulawesi Province. The city of Palu as the center of government and the heart of the economy in Central Sulawesi Province is located in the middle of the hammer valley and the center of the Palu-Koro plate fault which is an active fault so that it has quite

high tectonic activity. Communities living in coastal areas are very vulnerable to various kinds of disasters, such as hurricanes, storms, tsunamis, and heavy rains [3].

Figure 1. Research Location

Given the earthquake that was followed by the tsunami in Central Sulawesi, it is necessary to carry out integrated mitigation efforts to maintain the stability of the coastal area. Mitigation efforts are divided into two, namely structural and non-structural. Structural mitigation can be Soft Protection, namely making a green belt by planting mangroves or other vegetation in accordance with coastal characteristics.[5]

The vulnerability of coastal areas to natural disasters makes these areas require concepts in resilience. The community has an important role in making decisions for defend against disturbance, this refers to the system of social capital, response and capacity for adaptive action in survival [14]. Community resilience to disasters is increasing recognized as a powerful tool in providing support for decision-making in the field of disaster mitigation, risk assessment, and environmental, social, economic, or technological improvement [4].

  • II.    RESEARCH METHODS

  • A.    Research Time and Location

The method used in this research is descriptive method, namely by field observation, which is carried out to determine the existing condition of vegetation in the coastal area of Palu namely by ground checks at a number of points selected based on land cover from Google Earth satellite imagery of 23 survey points and Lansat TM 2019. The results of the classification of mangroves using the

CART method are used to determine the distribution map of mangroves in Palu Bay

Figure 2. Map of Palu Bay Mangrove Area

  • B.    Techical Sampling

Survey activities were carried out by observing the hue of the coastal environment and ecosystem characteristics including vegetation types, substrate types, beach characteristics and land use around the coast. Substrate characteristic data collection was on October 18, 2019 related to measurements of sediment carried out at 23 points while TSS (Total Suspended Sediment) 18 points were taken. Base sediment data collection was carried out using the Grab sampler tool. Prediction of water level using tidal data obtained from the results of tidal wave forecasting by the Geospatial Information Agency (BIG).

  • C.    Research Data Analysis

This basic sediment sampling was carried out at several observation points, where then the sediment samples were analyzed in the laboratory. In the process of sample analysis in the laboratory, the methods used in testing and analyzing samples follow the procedures of the Indonesian National Standard (SNI) No. 06-6989.3-2004 on the method of gravimetric total suspended solids (TSS) test [12].

  • III.    RESULTS AND DISCUSSION

The environmental hue and coastal conditions along Palu Bay are generally sandy and rocky beaches which are

dominated by coastal vegetation including Kekara Laut (Ipomoea pes-caprae), Spinifex littoreus, Crotalaria retusa, Calotropis gigantea on the coastal border which are influenced by tides; Various types of grasses and puzzles such as Cyperus pedunculatus, Cyperus stoloniferus; Types of trees such as Coconut (Cocos nucifera), Sea fir (Casuarina equisetifolia), Butun (Barringtonia asiatica), Nyamplung (Calophyllum inophyllum), Ketapang (Terminalia catappa), Chinese Kampis (Hemandia peltata), Waru (Hibiscus tilaceus). There are natural mangrove ecosystems in several locations located on the west coast including Palu City and the east coast including Donggala Regency with natural species such as Rhizophora apiculata, Avicennia lanata, Nypa fruticana, Rhizophora mucronata, Rhizophora stylosa, and Sonneratia alba.

Palu Bay as a natural landscape formation has estuaries in the form of semi-enclosed waters downstream river and has a reciprocal relationship with sea area. Therefore, the dissolved material from upstream to the downstream and empties into Palu Bay very affect the sustainability of the mangrove ecosystem. [9] The benefits of mangrove forests are to keep the coastline stable, protectbeaches and rivers from the dangers of erosion and abrasion, withstand storms/strong winds from the sea. [6].

Sediment is defined as materials derived from the breakdown of older rocks or materials derived from the weathering process of rocks and transported by water, air and ice, or materials deposited by naturally occurring processes such as chemical precipitation or secretion by organisms, then form a layer on the earth's surface [10].

Based on the results of the analysis, at 23 measurement points, it was found that the thickness of the fine sediment at the bottom of the water ranged from 1-10 cm while the results of the analysis of the thickness of the coarse sediment ranged from 1-26 cm. The sediment population in Palu City has the characteristics of Gravel (gravel) and Sand (sand). Texture is the appearance of sediments related to the size, shape, and arrangement of sediment grains. A sedimentary deposit is composed of various sizes of sediment particles originating from different sources, and this mixture of sizes is called the population. There are three groups of sediment populations, namely: 1. Gravel (gravel), consisting of individual particles: boulder, cobble and pebble. 2. Sand (sand), consisting of: very coarse, coarse, medium, fine and very fine sand. 3. Mud (mud), consisting of clay and silt [11]

The potential content of TSS in the water column reaches 188 mg/l, so an optimal layout design is needed to capture the sediment. Sediment deposition depends on the transport medium, where when the velocity is reduced the medium is unable to transport this sediment, resulting in accumulation [13]

Observation The highest and lowest tides reach 2 m, so it can be predicted that the value of tidal riding in 1 year can reach 3 m. Based on the results, the recommended mangrove species for planting are Rhizophora mucronata and Rhizophora apiculata, whose seeds come from the closest natural mangrove ecosystem. This species is very easy to breed and has a high survival rate if the environmental conditions are suitable.

Based on the results of the coastal substrate of Palu City after the Tsunami, it is to plan the formation of coastal forests in Palu City Bay. Coastal protection using vegetation (mangroves, sea pine, Ketapang, hibiscus, coconut, etc.) is a form of structural management known as soft protection. In addition to structural handling, there are non-structural measures, which include making laws and government regulations, regional regulations, law enforcement, establishing government and nongovernment organizations related to disaster management, providing disaster-friendly spatial planning concepts, providing databases and information systems. hazard and early warning, provision of tsunami hazard and risk maps, as well as making maps of evacuation routes and shelters (safe places), public education, and improvement of life support facilities.

Conceptually, [15] provides 7 cyclical steps in tsunami mitigation, namely: Involving relevant stakeholders, Determining the problem, Assessing available and required mitigation capacity, Identifying mitigation options, Evaluating these mitigation options and selecting actions, Implementing the implementation of mitigation actions, and Monitoring and evaluating the implementation of mitigation.

Based on the explanation above, the form of coastal protection with coastal forest (soft protection) can work well if it is supported by non-structural handling from both stakeholders and the community.

As for the rights and obligations of the community, as stated in Law [1] concerning Disaster Management, the community (everyone) has the right to:

  • (1)    Obtain social protection and a sense of security, especially disaster-prone community groups,

  • (2)    Obtain education, training, and skills,

  • (3)    Obtain written and/or verbal information regarding PB policies,

  • (4)    Participate in the planning, operation and maintenance of assistance provision programs,

  • (5)    Participate in decision making, especially those related to themselves and their community,

  • (6)    Supervise,

  • (7)    Obtain assistance to fulfill basic needs (especially for those affected by disasters), and

  • (8)    Obtain compensation due to disaster caused by construction failure.

Meanwhile, the community's obligations are:

  • 1)   Maintaining a harmonious social life of the

community,

  • 2)  Maintaining balance, harmony, harmony and

preservation of environmental functions,

  • 3)    Carry out disaster management activities, and

  • 4)    Provide correct information to the public about disaster management.

  • IV.    CONCLUSION

Based on the results of the research on the characteristics of the coastal substrate of Palu City, it shows that the suitable coastal vegetation in this location is the dry vegetation type, namely the Rhizophora type of mangrove. The results of the analysis, at 23 measurement points, it was found that the thickness of the fine sediment at the bottom of the water ranged from 1-10 cm, while the results of the analysis of the thickness of the coarse sediment ranged from 1-26 cm.

The sediment population in Palu City has the characteristics of gravel (gravel) and sand (sand). The potential content of TSS in the air column reaches 188 mg/l, so an optimal layout design is needed to capture the sediment. In addition to handling construction, non-structural handling includes making laws and government regulations, regional regulations, law enforcement, forming government and non-government organizations related to disaster management.

ACKNOWLEDGMENT

Thanks to the Ministry of Public Works. We also thank the research team for their help and support during the course of this research.

REFERENCES

  • [1]    Anonymous. 2007. Law Number 24 of 2007 concerning Disaster Management. State Gazette of the Republic of Indonesia of 2007 number 66: Jakarta.

  • [2]    BMKG. 2018. Meteorology, Climatology and

Geophysics                      Agency.URL:

http://www.bmkg.go.id/BMKG_Pusat/Informasi_C uaca/PrakiraanCuaca/PrakiraanCuaca Indonesia.

  • [3]    Bosello, F., & De Cian, E. (2014). Climate change, sea level rise, and coastal disasters. A review of modeling practices. Energy Economics, 46, 593– 605. https://doi.org/10.1016/j.eneco.2013.09.002

  • [4]    Cutter, S. L., Burton, C. G., & Emrich, C. T. (2010). Disaster Resilience Indicators for Benchmarking Baseline Conditions. Journal of Homeland Security and     Emergency     Management,     7(1).

https://doi.org/10.2202/1f47-7355.1732

  • [5]    Harada, K., Imamura, F. 2003. Study on The Evaluation of Tsunami Reducing by Coastal Control Forest for Actual Conditions. Asian and Pacific Coasts 2003 -2nd International Conference.

  • [6]    Irwanto. 2007. Vegetation Analysis for Management of Protected Forest Areas Marsegu Island, West Seram     Regency,     Maluku     Province

(thesis).Yogyakarta : Gajah Mada University.

  • [7]    Li, Z., Valladares Linares, R., Abu-Ghdaib, M., Zhan, T., Yangali-Quintanilla, V., & Amy, G.

  • (2014) . Osmotically driven membrane process for the management of urban runoff in coastal regions. Water      Research,      48(1),      200–209.

https://doi.org/10.1016/j.watres.2013.09.028

  • [8]    National Disaster Management Agency (BNPN), 2018. Report of Palu City Earthquake Victims”

  • [9]    Popular Scientific Book Publisher, Bogor. rasatriya, A. 2006. A Study of Sea Level Rise as a Basis for Overcoming Rob in the Coastal City of Semarang.

  • [10]    Rifardi, 2008. Sediment Texture: Sampling and Analysis. Pekanbaru. UNRI Press.

  • [11]    Rifardi, 2012. Modern Marine Sediment Ecology Revised Edition. Pekanbaru. UNRI Press.

  • [12]    Indonesian National Standard (SNI), 2004, Method of Gravimetric Total Suspended Solids (TSS) test, SNI 06–6989.3–2004

  • [13]    Tampubolon, S. 2010. Sediments in Muara Aek Tolang Pandan, North Sumatra. Thesis of Marine Science UNRI Pekanbaru.115 Journal of Sea Sand, Vol. 1, No. 2, 2006:31-42.

  • [14]    UNISDR. (2017). In support of the Sendai Framework for Disaster Risk Reduction. United Nation Office for Disaster Reduction (UNISDR).

  • [15]    Wi Diposaptono, S., Budiman, and Firdaus, A. 2009. Coping with Climate Change in Coastal Areas and Small Islands.

TABLE I

RESULTS OF MEASUREMENT OF SEDIMENT CHARACTERISTICS

No

Point

UTM 50N

Time (WITA)

Depth

Water (cm)

Sediment Soft (cm)

Sediment

X

Y

Hard (cm)

Result

1

PTS 20

817467

9902186

8:10:00 AM

68

2

2

2

PTS 13

817481

9902243

8:22:00 AM

250

5

10

3

PTS 11

817247

9902269

8:25:00 AM

201

12

17

4

PTS 10

817012

9902289

8:30:00 AM

220

10

15

5

PTS 9

816778

9902305

8:34:00 AM

240

3

17

6

PTS 8

816546

9902346

8:39:00 AM

245

3

17

7

PTS 7

816327

9902430

8:40:00 AM

280

2

3

8

PTS 12

816110

9902519

8:50:00 AM

211

-

-

Stone

9

PTS 19

816107

9902503

8:53:00 AM

150

-

-

Stone

10

PTS 14

816320

9902402

8:56:00 AM

150

-

-

Stone

11

PTS 15

816535

9902307

9:00:00 AM

100

-

-

Stone

12

PTS 16

816766

9902270

9:03:00 AM

110

1

1

13

PTS 17

817000

9902245

9:06:00 AM

150

10

5

14

PTS 18

817234

9902217

9:10:00 AM

87

5

14

15

PTS 6

817485

9902304

10:00:00 AM

271

1

15

16

PTS 4

817255

9902331

10:03:00 AM

281

8

21

17

PTS 3

817025

9902357

10:06:00 AM

255

5

20

18

PTS 2

816794

9902378

10:08:00 AM

240

6

26

19

PTS 1

816564

9902402

10:11:00 AM

255

5

35

20

PTS

816339

9902456

10:14:00 AM

265

10

25

21

PTS 5

816122

9902538

10:18:00 AM

119

-

-

Stone

22

310

817642

9902208

10:30:00 AM

145

5

0

23

311

817619

9902175

10:33:00 AM

100

10

5

TABLE II

RESULTS OF ANALYSIS OF TOTAL SUSPENDED SEDIMENT

No

Point

Easting

Northing

TSS (mg/L)

1

PTS 0

816339

9902456

74

2

PTS 1

816564

9902402

72

3

PTS 2

816794

9902378

63

4

PTS 3

817025

9902357

68

5

PTS 4

817255

9902331

84

6

PTS 6

817485

9902304

91

7

PTS 7

816327

9902430

68

8

PTS 8

816546

9902346

67

9

PTS 9

816778

9902305

58

10

PTS 10

817012

9902289

97

11

PTS 11

817247

9902269

76

12

PTS 13

817481

9902243

99

13

PTS 14

816320

9902402

122

14

PTS 15

816535

9902307

111

15

PTS 16

816766

9902270

188

16

PTS 17

817000

9902245

151

17

PTS 18

817234

9902217

147

18

PTS 20

817467

9902186

147