HYDROGRAPHIC SURVEY DETAIL-SANDAKAN

16.1 INTRODUCTION

This chapter briefly describes the hydrographic details of the Sandakan Coast both the present status as well as data available and some of the major issues of concern if any. The hydrographic details of each of the following are briefly discussed:

1. Islands.
2. Rocks and Sand Bars.
3. Reefs.
4. Sea Bottom.
5. Depths.
6. Tides and Current.
7. Siltation.
8. Hydrographic survey

16.2 PRESENT STATUS

16.2.1 ISLANDS

Presently, there are 8 major islands in the area of Sandakan as listed below. There is not much development on the coast of these islands at the moment except for residential and tourist purposes. Updating the coastline is in progress using aerial video mapping technique by the Department of Hydrography, RMN.

Major islands in the Sandakan area are:

Pulau Silingan.
Pulau Libaran.
Pulau Nunuyon Laut.
Pulau Nunuyon Darat.
Pulau Berhala.
Pulau Duyong.
Pulau Bai.
Pulau Timbang.

16.2.2 ROCKS AND SAND BARS

It has been known that submerged rocks are present in the south and southwest of Pulau Bai, north of Tanjung Siagil, south of Pulau Timbang and the coast between Pulau Tikus and Sungai Gum-Gum. These submerged rocks, because of their submerged nature poses dangers to vessels that navigate in the area.

Apart from submerged rocks, there are also two prominent sand bars in the area (1958 survey) which lies on the northern side of Sungai Kinabatangan and Trusan Duyong. The shape and orientation of these sand bars (and/or others) are subject to change (over time) due to changes of underwater currents as well as effect from the nearby river. Hydrographic survey is being carried out to update the data.

16.2.3 REEFS

In Sandakan area, coral reefs extend from the coast of Tanjung Gisow in easterly direction up to Pulau Nunuyon Darat, and the vicinity of Pulau Silungan, Pulau Gulisan, Pulau Libaran, Pulau Bangkawan, Pulau Tikus, Pulau Nunuyon Laut, Pulau Berhala and Pulau Bai.

Presently, it is very hard to predict the present status of the coral reefs in this area as no available data on the growth rates, conditions and the abundance of the coral reefs. No marine habitat survey has been done specific to this area by the Navy. Nevertheless, hydrographic survey is being carried out at present for the purpose of comparison and updating the data from the 1958 survey that was conducted for charting purposes.


16.2.4 SEA BOTTOM

The main components of sea bottom texture in the area are mud, sand, coral, rock and their mixture. Sea bottom also consists of other marine habitats such as seaweeds, seagrasses and other benthic organisms. No study or survey has been carried out to determine the condition and status of the sea bottom habitats.

16.2.5 DEPTHS

The depth pattern of the marine waters in the area varies considerably. At the western side, shallow patches cover a wide area of the waters with depth below 18 feet. At the northern side however, although the depth of the water measures a maximum depth of more than 84 feet, the navigable waters is constrained by islands and coral reefs with maximum depth of only 24 feet. At the eastern side, deeper water is found that are navigable by bigger vessel. At the Sandakan Harbour approach, the channel narrows down and is also restricted by Pulau Berhala and Pulau Duyong (1 mile wide) with a minimum depth 60 feet. The depth also decreases at the approaches of Pulau Bai and furtheocks are found.

Bathymetric survey is in progress to update the present nautical chart.

16.2.6 TIDES AND CURRENT

The tidal streams are generally influenced by stream from Balabac Strait (flood direction to south-easterly with rate of 1 knot) and stream from Sibutu Passage (flood directing to north-westerly with rate of 1 knot).

The tidal at Sandakan is mainly diurnal with a range of 2.8 metres (during astronomical tides) and at the rate of 1.25 knots during spring flood and 2 knots during spring ebb.

Current observation continuously for 32 days is in progress near Pulau Berhala overseen by RMN and is expected to complete by end of this month.

16.2.7 SILTATION

A survey was jointly conducted by the Sandakan Ports Authority, Royal Malaysian Navy (RMN) and Marine Police on 12th May 98 to find out if siltation is a problem in this area. The results of the survey showed that silting in the port area is negligible. A survey was also conducted by RMN ship on 7th May 98 to check if there is silting outside Sandakan port. The result of the survey showed that siltation is not a problem and the depth remains the same as per the chart. Charts of the survey result are appended for reference.

It is suggested here that periodical survey every six months at specific sites should be conducted to observe the changes of the depth for future expansion of marine activities as well as to keep the siltation problem in check.

16.2.8 HYDROGRAPHIC SURVEY

Hydrographic survey by the Department of Hydrography in collaboration with the Royal Malaysian Navy is currently in progress for the Sandakan waters. Data collection is expected to be completed by end of this month, while thorough analysis and compilation of results is expected to be completed by end of the year. The hydrographic details will be updated accordingly when the survey result is finalised.

16.3 AVAILABLE DATA

Apart from the siltation survey conducted in May 1998, most of the data used in this report are based on data from very old survey. These data are:

Hydrographic Details - British survey 1958 (Admiralty Chart 1649).
Meteorological Data - British Observation 1943 - 1970 (Pilots Book).
Tidal Information - RMN and National Mapping Department (1994 - 1996).

Other data for this section are shown in Figures 16.1-16.6

16.4 MAJOR ISSUES

The major issues of concern in the Sandakan waters that need to be addressed is the destruction of marine habitats particularly the coral reefs, seagrasses, seaweeds and to a large extend the fish population due to illegal activities such as fish bombing and other illegal fishing methods. Pollution by indiscriminate dumping of solid wastes from the ever increasing squatter population along the Sandakan coastal areas is also one of the major issues in the Sandakan waters. Measures on land reclamation along the coastal areas should also be taken to avoid siltation. Such measures will require concern, and the developers of coastal areas must comply with procedures of all relevant departments.

Figure 16.1: Average Observation of Meteorological Data 1942-1970

Figure 16.2: Tidal Range from 1994 – 1996

Figure 16.3: Islands within Sandakan District

Figure 16.4: Bathymetric Chart of Sandakan Waters

Figure 16.5: Sea Bottom Texture of Sandakan Waters

Figure 16.6: Tidal Stream Diagram for Sandakan Waters