5. MINDANAO

(Chart 4708)

Mindanao is the second island in point of size in the Philippines, having an area of about 36,906 square statute miles and a length of general shore line of about 1,383 miles. It has a very irregular shape, the coast line being indented with deep bays and inlets. The large bays, Iligan on the north and Illana on the south, nearly sever the island in two, the isthmus between them being only about 72 miles wide at the narrowest part, at the head of Panguil Bay.

The island is mountainous and drained principally by two large rivers, the Agusan and the Rio Grande de Mindanao. The volcano of Mount Apo, situated westward from Davao Gulf, rises to a height of 9,690 feet (2,953 m.) and is probably the highest point on the island and in the Philippine Archipelago.

The Agusan River has its sources in the comparatively low divide that separates this valley from the one making north from Davao Gulf and flows northerly into Butuan Bay on the north coast. The river is navigable by small ocean-going steamers of 12 feet (3.7 m.) draft to Butuan, about 5 miles up from its mouth. Small boats and launches of 4 feet (1.2 m.) draft can ascend the river about 70 miles. The valley land tributary to the Agusan River is about 1,000 square miles in extent.

The Cotabato Valley or Basin, an extensive plain with several large lakes and rivers, is drained by the Mindanao River, which, having formed an extensive delta, empties through two main channels into Illana Bay near Bongo Island. Small steamers of 7 feet (2.1 m.) draft cross the bar at high tide and ascend the north channel 5 miles to the town of Cotabato. Launches of 312 feet (1.1 m.) draft can ascend the river 60 miles farther. The fertile valley traversed by this river is about 30 miles in width and shows scarcely any change of level. The area of the valley, not including Lake Bulan and Liguasan Marsh, is about 1,800 square miles. The Cotabato Valley is separated from the valley to the north of Sarangani Bay by a low divide.

The whole island, being less than 10 degrees from the Equator, has a hot and humid climate, more equable than Luzon. It is under the influence of the monsoons of the Northern Hemisphere, but it is largely below the typhoon region. It has all the products of the other islands of the archipelago; hemp, copra, lumber, and rice being the principal exports. About half the population is classed as nonChristian.

Mindanao is connected with the general telegraph system of the islands by cable and radio. Zamboanga and Davao are the largest commercial ports, but only small quantities of general supplies are available. They are ports of entry and are connected with Manila and other cities of the Philippines Islands by several lines of steamers. Foreign vessels call frequently, Davao being a regular port of

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call for vessels from Japan. The north and east coasts of Mindanao are served by steamers out of Cebu and Iloilo. A system of roads is now being rapidly extended throughout the island and connection is afforded between the towns on the north coast and southward across the island to Cotabato and Davao.

NORTH COAST OF MINDANAO

(Charts 4603, 4604, and 4605)

Winds. Both monsoons blow with strength on this part of the coast and, together with the tidal currents from the Strait of Surigao, raise a chopping sea. During the southwest monsoon the land breezes are regular; they blow from sunset to morning and shift sometimes to southeast and east-southeast, but during collas the wind remains steady at southwest. Colla is the name given in the Philippines to a southwest gale that blows occasionally during the months from July to October, with violent squalls and much rain.

During the northeast monsoon the land breezes are not regular, but still they are experienced when the monsoon is established, and the winds vary from north to northeast and east-northeast. The coast is very exposed at that season.

In navigating under sail, in either monsoon, the coast of Mindanao should be approached in order to profit by the land breezes; but care must be taken to guard against the violent squalls that come off the mountains.

Currents. Between Surigao Strait and Camiguin Island there is a constant current to the west in both monsoons, varying in strength according to wind and tide. The flood stream entering through Surigao Strait passes southwest on both sides of Camiguin Island with considerable velocity, but loses its strength as it enters Macajalar Bay; with spring tides it flows with an estimated velocity of 2 to 3 knots. South of Bohol the currents follow the direction of the prevailing monsoon. Near the coast and in the great bays the currents are influenced by the discharge from the rivers.

BILAA POINT TO BAGACAY POINT (Charts 4603 and 4647).— Bilaa Point, latitude 10°49'.5 N., longitude 125°26' E., the northern extremity of Mindanao, is the termination of the range of mountains that traverses the east coast from north to south; the point itself is of dark rock, clean and fringed by a narrow steep-to reef.

Bilaa Shoal, composed of sand and dark coral heads and covered by a least depth of 2 fathoms (3.7 m.), lies 3/4 mile northward from Bilaa Point, from which it is separated by a deep channel over 11⁄2 mile wide; vessels using this channel should pass between 14 and 12 mile from the shore. The position of the shoal is usually indicated by tide rips. During the southwest monsoon, anchorage can be found on the slope of this shoal, sheltered from the tide streams.

Madilao Point, about 4 miles southwestward from Bilaa Point, is 270 feet (82 m.) high, clean and steep-to, and composed of dark rock. It forms with Bilaa Point a deep bay which extends about 1 mile southeastward and affords anchorage sheltered from northeast to southwest through east but necessarily close in because of the great depth of water.

From Madilao Point the coast trends southward for 46 miles to the mouth of the Agusan River. From Madilao Point to Mount Tubay it consists of the western slope of two mountain ranges and is high, bold, clean, and steep-to, and there are no off-lying dangers. The small settlements along the shore are points of call for small coasting vessels.

Mount Tubay, at the southern end of this section of the coast is a prominent hill which rises to a height of 1,468 feet (447 m.).

BUTUAN BAY, about 20 miles wide at the entrance between Tubay and Diuata Points, extends 10 miles southward and is deep and clear. The eastern shore from Mount Tubay to the mouth of the Agusan River, in the southeast angle of the bay, is low, densely wooded, and fringed by a sandy beach, off which shoal water with very deep water at its edge extends to a distance of 1/2 to 3/4 mile. The southern shore of the bay, between the Agusan River and the town of Nasipit, 10 miles westward, is low and wooded to the sandy beach. Scattered houses and clearings exist on this stretch of coast, and the shore line is intersected by small, unimportant streams. Shoal water does not extend more than 1/2 mile from the shore between these two points. The shore line near Nasipit is such that tangents around the harbor entrance must be used with great caution. From Nasipit to Diuata Point, about 10 miles northwestward, the shore is fringed by a reef which varies in width from less than 1/4 to 1/2 mile.

Tubay and Cabadbaran, lying about 1 and 311⁄2 miles, respectively, southward from Mount Tubay, are the only towns on the east shore of the bay. They are small and of little commercial importance and are only occasionally visited by coasting vessels.

Cabadbaran Light, latitude 9°07′22′′ N., longitude 125°31′20′′' E., marks the entrance to the port of Cabadbaran. The light is fixed green, visible 7 miles, and is displayed at an elevation of 33 feet (10.1 m.) above mean high water from a white steel cylindrical tower located on the western extremity of the south shore of the mouth of the river.

The Tubay is a swift-running stream with very little water on its bar at low water. It is understood that natives pole canoes up it to Lake Mainit, and also that there is an island passage for canoes between the Tubay and Agusan Rivers. There is no anchorage off the river mouth, but vessels occasionally anchor in from 12 to 15 fathoms (21.9 to 27.4 m.) about 7 mile 347° true from the town and 3 mile from shore.

The bar of the Cabadbaran River bares at low water, and there is no anchorage off it. Anchorage can be found southward of a sand pit which extends westward from the south bank of the river. From abreast of this anchorage there is a good road leading to the town of Cabadbaran. There is a fair road between Cabadbaran and the mouth of the Agusan River.

AGUSAN RIVER (Chart 4647), which discharges into the southeast angle of Butuan Bay, is the second largest river in the island of Mindanao. Its mouth is divided into two channels by Pontod

Island, a small sandy cay with a settlement and a coconut grove on its southern end. The bar of the northern entrance, blocked by stones sunk there for the purpose, has a depth of only 3 feet (0.9 m.) and is not used for navigation. The western entrance has a width of about 150 yards at the narrowest part, and 9 or 10 feet (2.7 or 3.0 m.) may usually be carried over the bar at low water and 12 to 14 feet (3.7 to 4.3 m.) at ordinary high water.

Anchorage. There is no good anchorage outside of the entrance, the water being very deep and the bar steep-to. Good anchorage for small vessels which do not intend to ascend the river may be found at the mouth of the Baug River, which enters the Agusan just inside the bar. The rainy season begins in December and lasts about 4 months. The river during these months is very high and filled with floating debris, most of which can be avoided by anchoring under the lee of a point.

The point of land on which Magallanes is located has receded about 135 yards and the white monument which formerly marked the spot where Magellan celebrated the first mass in the Philippines has disappeared.

Range and light.-The best water across the bar is marked by a range, bearing 94° true, consisting of three beacons on the eastern side of the Baug River. The outer beacon is a pile structure, painted white, carrying a triangular-shaped target, point up; the middle beacon is a concrete tower surmounted by a red light visible 7 miles; the inner beacon is a concrete tower carrying a triangular-shaped target, point down. This target is white with a black vertical stripe through the center.

A natural range for crossing the bar, sometimes used by local pilots, is the tangent to the coconut trees south of Magellanes in line with two high trees eastward of the Baug River. There are no regular pilots in attendance but strangers are advised to arrange for local pilots before attempting to enter the river.

Directions.-Vessels entering the Agusan should bring the beacons on the bearing 94° true and steer for them, keeping a good lookout for shoal water on either side. In April 1938 the range lead about 100 feet off the fish traps on the south side of the channel. There is a hard gravel shoal extending about 1/4 mile southward from the south side of Pontod Island. When within about 1 mile of Magallanes the vessel should be hauled southward and the eastern side of the channel favored until the mouth of the Baug River is passed, after which the usual rules for river navigation should be followed.

A house in Tortosa in range with Mount Maiyapay clears the shoals on the north side of the entrance to the Agusan River. When coming from the westward the river entrance will be found to lie on a bearing southward of the southernmost of the two small groups of hills inland from Magallanes.

Butuan, the capital of Agusan Province, lies on the west bank of the Agusan River, about 5 miles from the sea. From the bar to the town, depths of from 212 to 5 fathoms (4.6 to 9.1 m.) may be carried. The current in the river is strong and the water off the town is fresh at all stages of the tide. Butuan carries on a considerable trade in hemp and copra, principally with Cebu. There is regular motor vessel connections; gasoline, Diesel oil, and ice are available in small

quantities. There are several small hospitals and a radio station is maintained by the Bureau of Posts. The town has no machine shop.

There are two marginal wharves, the upper, however, provides landing only for launches. The downstream wharf has a controlling depth of 14 feet (4.3 m.) alongside and consists of a timber deck and apron on concrete piles. There is a small cargo shed on the wharf. Vessels anchoring in the stream should lie below the upper wharf, as the river higher up is contracted by a shoal making off from the west bank.

NASIPIT HARBOR (Chart 4647) is formed by an opening between bluff rock headlands about 3 mile apart and extends about 1 mile southward. The village of Nasipit lies on the bluff forming the eastern entrance point. There is telephone and autobus connection with Butuan. Foreign vessels call regularly to load logs, and coasting vessels maintain communication with Cebu. A large quantity of copra is produced here, and the coconut groves with the bluffs forming the entrance are good landmarks for making the harbor.

The outer harbor is an excellent one for moderate-sized vessels, having depths of from 6 to 9 fathoms (11.0 to 16.5 m.) over an anchorage area about 3/4 mile long by about 300 yards wide. The inner harbor is contracted by shoal water and is practicable only for small craft. Both entrance points to the outer harbor are fringed by reefs which show plainly on a clear day. The reef on the eastern side continues much farther in than that on the western side and the sand spits apparently extend farther into the channel than charted. In April 1938 two privately maintained white buoys marked the western edge of the shoal water.

Nasipit Harbor Light, latitude 8°59'04" N., longitude 125°19'48'' E., is displayed at an elevation of 94 feet (28.7 m.) above mean high water from a white concrete tower located on the bluff on the western shore of the harbor about 2 mile from the entrance. The light is flashing white every 5 seconds and visible 15 miles.

Directions.-Steer a 215° true course for the light, when the northwest point at the entrance bears 325° true, change course to 180° true and continue to an anchorage in midchannel southward of the light.

The reef on the western side of the entrance to Nasipit Harbor extends about 1/4 mile northeastward from the western entrance point, then curves around to the westward, with a point extending northward for about 3 mile, and then follows the coast about 1/2 mile out for about 3 miles, when it narrows to less than 1/4 mile and extends to and around Diuata Point into Gingoog Bay.

Diuata Point, the western entrance point to Butuan Bay, is low, densely wooded, and rises gradually to a height of 1,165 feet (355 m.) at a distance of about 3 miles inland. The coast is formed of coral with coral sand beaches and is fringed by a very narrow, steep-to reef, which widens to 150 yards westward of the point.

GINGOOG BAY, between Diuata and Sipaca Points, is 20 miles wide at the entrance and extends about 13 miles southward. The shores of the bay are fringed with very narrow, steep-to coral reefs, the