DRONE AND CORAL REEF MEASUREMENT CAUSED 

BY VESSEL GROUNDING IN KARIMUNJAWA NATIONAL PARK

(CASE STUDY OF GOSONG SELOKA)

Isai Yusidarta¹, Nugroho Dri Atmojo²

1&2) Center of Karimunjawa National Park

1)isaiyusidarta@gmail.com

2)driatmojo@gmail.com

Translator : Adinda Nurul Islami (Ministry of Environment and Forestry)

Abstract: Activities like illegal fishing and illegal pilot often happened in shallow water of Karimunjawa National Park. These actions lead to vessel grounding causing the damage of coral reef ecosystem. One of coral damage happened in Gosong Seloka at 2 February 2018. To accomplish a settlement of environmental dispute in accordance with Act Number 32 year 2009 consideration of Protection and Management of Environment, environmental loss must be claimed based on the damaged area. Measurement of damage area that had been done before used fishbone ground-truth method. The technique of this method used mooring buoys placed at the outer points of the damage area. It was to estimate damaged area before ground truth was done by several scuba dives. All these steps were done without the help of drones.

The aims of this research are to observe the benefit of drone application as a means of coral reef measurement in Gosong Seloka, Karimunjawa National Park and to quantify the damage area of coral reef ecosystem.

The method used in this research was an observation that had been done in the location of vessel grounding, that is Gosong Seloka, shallow water of Karimunjawa National Park. The result of this survey provided description about the data comparison of drone technique, drone and snorkelling technique, and drone and ground-truth measurement technique. The survey was conducted at 20-21 April 2018.

The result in this research showed that the use of drone for aerial mapping in vessel grounding site in Gosong Seloka gives prior image of coral reef damage and helps the application of fishbone technique easily. By using drone technique, the researchers got 16 polygon spots of coral reef ecosystem damage with total area at 155m². By using drone and snorkelling technique, the researchers got 14 polygon spots and 161m² of total damage area. Meanwhile, by using drone and ground-truth measurement technique, the researchers got 14 spots with total damage area at 184,45m².

Based on the result above, drone and ground check cannot be separated. It was better to apply them together on doing measurement of damage area because aerial mapping alone still cannot outline the area of dispersal damage. The aerial mapping provided can only show trajectory damage zone. This condition also needed ground checking to specify the damage whether it was because of vessel grounding or bleaching.

The conclusion of this research was drone can contribute to locate the coral reef ecosystem damage area in Gosong Seloka, Karimunjawa Nationa Park. Total damage area claimed as environmental loss is 184,45 m².

Keywords: drone, fishbone, ground-truth

Foreword

Karimunjawa National Park is a conservation area established as a nature conservation area based on Minister of Forestry and Plantation Decree Number 78/ Kpts-II/1999 date 22 February 1999 with total area of 11.625 hectare. The area was divided into waters area of 110.117,3 hectare and 1.507,7 hectare. The management of Karimunjawa National Park has already applied zoning system for dividing the area with community based system. It had been established in Decree of Director General Number 28/ IV/set-3/ 2012. Karimunjawa National Park can only be used for activities in the field of education, research, cultivation, and natural tourism.

Karimunjawa National Park was situated in the middle of heavy traffic area. Vessels, in any kinds and shapes, were moving back and forth Karimunjawa National Park area. The vessel came from north (Kalimantan) to south (Java north beach) and from east (Jakarta’s harbour) to west (Surabaya’s and East Indonesi’s harbors). The common vessel that crossing Karimunjawa National Park area were passenger vessel, cargo vessel, both for general and special used, tanker, and tugboat – barge and landing craft tank (LCT). 

Image 1. Karimunjawa National Park was situated in the middle of commercial vessel intersection area based on marine traffic site.

Karimunjawa National Park area actually was not vessel crossing area. There were no vessel lanes prepared for commercial vessel. This can be seen in the international navigation e-chart. However, there were commercial vessels crossing this area, especially tugboat – barge and LCT which cross Karimunjawa water without notice. This could harm the coral reef ecosystem and navigation safety.

The growing development of East Indonesia and the demand of energy resources, particularly coal in Java have made Karimunjawa National Park water area crowded with commercial vessels. In 2017 until 2018, there were 6 vessel grounding cases happened around Karimunjawa National Park shallow waters that lead to coral reef destruction. In terms of settlement of environmental dispute of these cases, the measurement technique of coral reef damage area was needed. This technique has to be accepted by both dispute parties. The aims of this research were to observe the benefit of drone application as a means of measuring coral reef damage area in Gosong Seloka, Karimunjawa National Park shallow waters and to quantify the total area of coral reef damage caused by vessel grounding.

RESEARCH METHOD  

Doing an observation is not only observing objects but also using all the senses to see, to hear, to think, to smell, and to feel. The observer has to avoid being subjective towards the result of the research (Indriantoro dan Supomo, 1999).

This observed the vessel grounding cases happened in Gosong Seloka by applying 3 techniques, that are drone technique, drone and snorkelling technique, and drone and ground-truth measurement technique. This observation used drone (unmanned aerial vehicle) as a means of applying the three techniques mentioned. The drone used was Phantom 4 equipped with 4.000 x 3.000-pixel camera.

Drone technique was measuring coral reef damage area by analysing aerial mapping image captured by drone. This technique required observers to differentiate between damage condition area caused by vessel grounding and good condition area. The steps that had to be done in this technique were 1) Observers made a drone operation planned above vessel grounding location; 2) Observers operated drone; 3) Observers analysed aerial mapping image captured to get damage position and area.

Drone and snorkelling technique was the combination of measuring coral reef damage using drone and observation while swimming on the surface of water (snorkelling). The steps taken were 1) Observers memorized the aerial mapping images taken previously with drone; 2) Then observers made a point sketch on a slate; 3) Observers snorkelled to check the point he sketched before; 4) Observers wrote down all the points he saw while snorkelled; 5) after finishing the observation, observers analysed all the data with GIS program.

Drone and ground-truth measurement was the compilation of all the techniques mentioned above. In this technique, the observers needed to scuba dive to directly measure the damage on the coral reef. The steps of this technique were 1) Observers memorized the aerial mapping images taken previously with drone; 2) Then observers made a point sketch on a slate; 3) Observers snorkelled to check the point he sketched before; 4) with certain consideration, observers did the ground-truth measurement on the coral reef damage point using 1 meter x 1 meter square grid and 10 cm x 10 cm on each grid; 5) Observers measured on each patch damage by scuba diving; 6) Observers wrote down all the results found.

Some consideration of measuring coral reef damage area using square grid were 1) the area of coral damage was irregular; and 2) the damage spot locations spread out.

The distinct damage characteristic on the status of this colony of coral was categorized by estimating the percentage of mortality and partial mortality on dead coral (Gomez et al 1994, Ginsburg et al 1998, DeVantier and Done (2007) was 1) coral mortality on the direct impact area (m²) = (M + PM/2), M = amount of full box dead coral, PM (partial) = amount of half full box; and 2) on the indirect impact area (dispersal zone), the wreckage, shard, or broken fragments of coral around the perimeter of patch damage, the calculation was based on long circle (k) with formula of circle (m²) = p r².

The result of coral mortality area applied by square grid method was an absolute value of dead coral of direct impact area. A vast coral damage of indirect impact area (dispersal zone) was spread of wreckage, shard, or broken fragments of coral that still had survival possibility (coral of opportunities).

RESULT AND DISCUSSION

Vessel grounding in Gosong Seloka happened at 2 Februari 2018, was the first case of grounding caused coral reef ecosystem damage in 2018. Vessel grounding coordinate position was on S.05⁰ 51.290’ dan E. 110⁰ 29. 276’ that was in the Gosong Seloka water in particular Traditional Fishing Zone. Centre of Karimunjawa National Park and Directorate of Environmental Dispute Settlement conducted ground verification on the grounding site.

Environmental dispute settlement is based on Act Number 32 year 2009 consideration of Protection and Management of Environment and Government Regulation Number…… When verification was conducted, team from Centre of Karimunjawa National Park who joined the Join Survey Team, also conducted a research. The team analyzed the measurement of coral reef damage by using 3 techniques, namely drone technique, drone and snorkelling technique, and drone and ground-truth measurement technique.

• drone technique

The technique depends on the drone ability on doing aerial mapping and observers’ ability to analyse images taken by drone with GIS program. Observers has to be able to distinguish good coral reef image and broken coral reef image.

Image 2. Calculation result of coral reef damage in Gosong Seloka by using drone technique.

The image shows broken coral reef, delineation was done to get a polygon that can be used to give information about a vast coral reef damage information in terms of meter square automatically. The result of image analysis showed 16 damage points (patch damage) in variation wide range. The result of delineation shows that each wide damage point was varied from 0,51 m² until 54,2 m². Total delineation area is 155m² (image 2).

• drone and snorkelling technique

This technique was the combination of drone technique and observers’ ability to distinguish coral damage caused by vessel grounding or other reasons. This was done by snorkelling to explore the damage area.

Image 2. Calculation result of coral reef damage in Gosong Seloka by using drone and snorkelling technique.

The analysis result of drone aerial mapping and snorkelling ground check. Observers was not only memorizing the images but also making sketch on the slate to be brought when doing snorkelling ground check. This sketch was used to help the observers to memorize and compare the image and the real condition.

The result of this compilation technique showed only 14 spots damage with total damage area 161 m². It was different in 2 spots of aerial mapping from drone technique. By doing snorkelling, the observers can identify that the other 2 spots showed on drone technique was caused by bleaching that maybe caused by global warming or fishing technique using potassium cyanide.

• drone and ground-truth measurement technique

Image 3. Type of coral reef damage in Gosong Seloka using drone and ground truth measurement technique

Based on the observation result, coral reef damage is divided into 2 types, that are 2 spots of massive damage on 1 m until 2 m, and 12 partial damage types on 3m, 4p until 14p (Image 3). Massive type can be divided into two, that are massive damage on the spot 1m and 3 m and absolute damage on the spot 3m, 4 p until 14p on the patch-reef part. Meanwhile, partial type occurred on the bellow part of patch-reef caused by shards from the upper part. Coral damage characteristics and coral death also per spot wide range area can be seen in the Table 1 and 2.

Table 1. Spots of direct impact of coral reef damage (quadrant grid area)

No.	Damage Spots (Direct)	Damage Characteristics	Quantity	Absolute Area (m2)	Mortality (%)
1.	Massive damage 1m Depth 0.5m	Montipora, Acropora, and others crushed, cut off (fragments, rubble)	60	50.93	100
2.	Massive damage 2m Depth 0.75m	Montipora, Acropora, Favites, Favia and others crushed, cut off (fragments, rubble)	45	41.28	100
3.	Patch damage 3m Depth 2-3m	Porites massive, mix species crushed, cut off (fragments, rubble)	8	6.42	100
4.	Patch damage 4p Depth 1m	Porites massive, mix species crushed, cut off (fragments, rubble)	10	9.10	100
5.	Patch damage 5p Depth 0.5m	Porites massive crushed, cut off (fragments, rubble)	2	1.58	100
6.	Patch damage 6p Depth 1m	Porites massive crushed, cut off (fragments, rubble)	1	0.82	100
7.	Patch damage 7p Depth 2m	Porites massive crushed, cut off (fragments, rubble)	3	1.66	100
8.	Patch damage 8p Depth 2m	Porites massive, mix species crushed, cut off (fragments, rubble)	3	1.85	100
9.	Patch damage 9p Depth 1m	Porites massive crushed, cut off (fragments, rubble)	2	1.21	100
10.	Patch damage 10p Depth 1m	Porites massive, mix species crushed, cut off (fragments, rubble)	5	2.00	100
11.	Patch damage 11p Depth 2m	Porites massive, mix species crushed, cut off (fragments, rubble)	4	2.66	100
12.	Patch damage 12p Depth 2m	Porites massive, mix species crushed, cut off (fragments, rubble)	4	3.46	100
13.	Patch damage 13p Depth 2m	Porites massive crushed, cut off (fragments, rubble)	2	1.26	100
14.	Patch damage 14p Depth 3m	Porites massive crushed, cut off (fragments, rubble)	5	3.74	100
	Total	154	127.97	100

Sources: Processed primary data

Based on direct measurement, observers divided the coral reef damage area into two, they are direct impact area or can be called trajectory zone or hull footprint and indirect area or dispersal zone.

In direct impact area, the remnant of vessel grounding can be clearly seen (trajectory/hull footprint). This was the main area where vessel body grounded, hit, and crashed. In this area, the damage categorized as massive damage type on the various kind of colony of corals. This type was characterized as colony of coral crashed and cut off and had 100% mortality (Table 1).

Indirect impact area contained broken coral fragments that fell around the main damage area. Indirect damage area can be called dispersal zone and characterized as partial damage type. Partial damage type was the damage on one or more colony of coral that was largely spread out. It can be coral ruins in terms of rubble fragments/sediments (Table 2).

Table 2. Spots of indirect impact coral damage (coral of opportunities)

No.	Damage Spots (Direct)	Damage Characteristics	Quantity	Absolute Area (m2)	Mortality (%)
1.	Mass. dispersal 1m	Rubble fragmentation / meld sediment	0	0	100
2.	Mass. dispersal 2m	Rubble fragmentation / meld sediment	0	0	100
3.	Patch. dispersal 3m	Rubble fragmentation/ sediment	10.10	1.70	50%
4.	Patch dispersal 4p	Rubble fragmentation/ sediment	18.7	18.74	50%
5.	Patch dispersal 5p	Rubble fragmentation/ sediment	5.3	0.66	50%
6.	Patch dispersal 6p	Rubble fragmentation/ sediment	4.6	0.86	50%
7.	Patch dispersal 7p	Rubble fragmentation/ sediment	8.3	3.82	50%
8.	Patch dispersal 8p	Rubble fragmentation/ sediment	9.2	4.89	50%
9.	Patch dispersal 9p	Rubble fragmentation/ sediment	5.9	1.56	50%
10.	Patch dispersal 10p	Rubble fragmentation/ sediment	10.7	7.12	50%
11.	Patch dispersal 11p	Rubble fragmentation/ sediment	8	2.44	50%
12.	Patch dispersal 12p	Rubble fragmentation/ sediment	8.6	2.43	50%
13.	Patch dispersal 13p	Rubble fragmentation/ sediment	7.73	3.50	50%
14.	Patch dispersal 14p	Rubble fragmentation/ sediment	12.53	8.76	50%
	Total		109.66	56.48	50%

Sources: Processed primary data

Table 3. Calculation result of coral reef damage area in Gosong Seloka caused by vessel grounding

No.	Damage Spots	Area (m2)	Mortality (%)
1.	Direct Impact: Absolut damage (3m, and 4p – 14p)	35,76	100
	Massive damage (1m – 2m)	92,21	100
2.	Dispersal zone 3m, 4p – 14p (coral of opportunities)	56,48	50
	Total coral reef damage in Gosong Seloka	184,45

Sources: Processed primary data

The measurement using drone and ground-truth measurement resulted the damage area in Gosong Seloka at 184,45 m². Related to Table 3, 100% mortality happened in 1m and 2m damage spots, because the damage was so massive. It was crumbled away making a V shape. 100% mortality also happened on the 3m and 4p-14p spots at the upper part of patch-reef. It was caused by a friction of ship’s hull. 100% mortality also happened in the direct impact area.

At the indirect impact area, at damage spots 3m, and 4p-14p, the estimated mortality percentage only reached 50% (that means that the mortality and immortality chance at 50%). Mortality percentage can be higher as time goes by, that means the longer measurement done the higher percentage of mortality appear.  

Image 2. Photos showing characteristics and types of coral reef damage caused by vessel grounding in Gosong Seloka, Karimunjawa National Park.

Comparisons of the three techniques

The analysis of differentiation of coral reef damage measurement based on the drone technique, drone and snorkelling technique, and drone and ground-truth measurement technique can be seen on the Table 3. The smallest area of coral reef damage based on drone technique was 155m. This number occurred because the images captured by drone was blocked by the depth of water. It was hard to capture the damage of coral reef when the depth of water was more than 5 meters, even when the water is clear. Ground check was still needed to make sure the damage.

Doing ground check by Snorkelling helped correcting the measurement of coral reef damage, the amount of damage spot, and the cause of the damage. In image 1 and image 2, polygon delineation line on Image 2 was wider after snorkelling ground check done. Damage spots decreased into 14 spots, the other 2 spots were missing. Snorkelling ground check that had been done before clarified that the 2 spots missing was because of bleaching. The damage was not because of vessel grounding.

Table 3. The comparison of three techniques of coral reef damage measurenment in Gosong Seloka

No.	Description	Drone Technique	Drone and Snorkeling Technique	Drone and Ground-Truth Measurement
1.	Coral Reef Damage Area	155m2	161 m2	184,45 m2
2.	Coral Reef Damage Spots	16 spots	14 spots	14 spots
3.	Coral Reef Damage Caused	Cannot be distinguished	Bleaching and vessel’s ground	Bleaching and vessel’s ground
4.	Types of Coral Reef Damage	Cannot be distinguished	Cannot be distinguished	Massive and partial types

Sources: Processed primary data

Coral reef damage area based on ground-truth measurement technique was 184,45m. This technique completed the other techniques. Identification became clearer.  Damage spots on ground-truth measurement were still the same compared to the drone and snorkelling technique. Bleached coral reef were still growing and fragmentation rubble on the below part of patch-reef were not found. Another benefit of ground-truth measurement technique was the observers can easily identify types of coral reef damage.

The main advantage of ground-truth measurement technique was this technique allowed observers to carry standard measurement equipment while diving and doing detail measurement in damage locations. Ground-truth measurement technique supported coral damage measurement that cannot be measured clearly just by aerial mapping images captured by drone technique. Drone can capture massive type of coral reef damage, whether it was massive damage or absolute damage that located in the upper part of patch-reef. Captured image looks solid and clear white. While, in partial coral reef damage type at dispersal zone, drone cannot capture the aerial mapping image clearly, because this damage type was located in the lower part of patch-reef (deeper location) and it broke up into diverse size. Some of the corals broke into tiny pieces even into fine sediment that can cover coral polyps. It caused coral death. Because it broke up and rubble fragmentation was smaller, it cannot provide clear white solid images.

Drone was the means that provides image of vessel grounding location in Gosong Seloka. This image gave early information related to different sight pictures in coral reef area. Coral reefs were effected by vessel grounding looked like a solid white image on the picture taken by drone. But the information given from this image was still invalid until ground check done. Ground check was needed to confirm that this white solid image was because of vessel grounding. The data confirmed from ground check showed that there were 2 damage spots caused by bleaching. That meant aerial mapping images taken by drone still needed to be confirmed through ground check. This helped to ensure there was coral reef damage in a specific location. Drone can also be an early guidance before coral reef damage measurement conducted through ground check. This also reduced area and time needed for conducting measurement.

Coral reef damage measurement, specifically in vessel grounding case, must have scientific measurement method so the measurement done can be accepted in environmental dispute settlement, whether the settlement done out of court, in court, and through administration sanction. Makin delineation based on drone aerial mapping is not the only method to relied on, since this method had some limits that had been mentioned before. Besides using scientific method and logic, the measurement also needed standard measurement equipment, such as measuring tape with SNI.

CONCLUSSION

Based on the result of the research and discussion above, we can conclude that:

1.      The use of drone as a means that can provide early information related to coral reef damage caused by vessel grounding in Gosong Seloka Karimunjawa National Park helps ground check process.

2.      The coral reef damage area in Gosong Seloka was 184,45m².

REFFERENCES

DeVantier LM, Done (2007). Inferring Past Outbreaks of The Crown-of Thorns Seastar from Scar Patterns on Coral Heads (in Geological approaches to coral reef ecology) Editor. RB Aronson. Springer, p85-125.

Ginsburg, Robert N.; Gischler, Eberhard; Kiene, William E., 2001. Partial mortality of massive reef-building corals: an index of patch reef condition, Florida Reef Tract. Bulletin of Marine Science, Volume 69, Number 3, November 2001 , pp. 1149-1173(25).

Gomez ED, Alino PM, Yap HT, Licuanan WY (1994) A reviewof the status of Philippine Reef. Mar Pollut Bull 29: 62-68

   Indriantoro, N., dan Supomo B. (1999). Metodologi Penelitian Bisnis untuk Akutansi dan Manajemen. Yogyakarta. BPFE.