Mactan Channel getting shallow

CEBU CITY — It is only a matter of time before the Mactan Channel will no longer be navigable by ships.

Over the years, the Mactan Channel has decreased in depth owing to heavy siltation and sedimentation and indiscriminate garbage disposal.

Marine biologist Danilo Largo said the Mactan Channel has become shallow with the deepest portion at about 20 meters and the shallow areas at about eight meters. Most ships navigating the waterway must at least have a draft of eight meters.

Largo was with the Mactan Channel Multisectoral Management Council, a team of biologists and pollution consultants who conducted water quality monitoring at the channel the other day.

While the team focused their research on salinity, temperature, dissolved oxygen, turbidity and the quality of water at the Mactan Channel, little did they expect that they would instead find it to be getting shallow.

The Mactan Channel extends from the coastal city of Talisay to the municipality of Consolacion.

Pollution control officer Ivy Tariman attributed the decreasing depth to indiscriminate garbage disposal, heavy siltation and sedimentation and the absence of a study that would monitor the rate of sedimentation that finds its way into the channel.

The Mactan Channel is the depository or "sink" of seven tributaries in Cebu City — the Mananga, Busay, Batuan, Guadalupe, Mahiga, Cansaga and Butuanon rivers.

Tariman said the volume of silt deposited in the channel has increased through the years owing to heavy erosion of riverbanks. But more than that, lapses in waste management have also contributed to increasing silt deposits. The city‘s drainage and sewage systems all find their way to the Mactan Channel.

Tariman said, "Garbage or solid waste from households are dumped into the river and this too is drained into the sea. People usually think that garbage is just washed out into the sea. But what they throw out can also find its way to the Mactan Channel where it stays, and this also contributes to shallowing of the waters."

What has caught the attention of the researchers is the absence of previous studies to monitor the rate of sedimentation as a result of riverbank erosion or garbage disposal.

The absence of a sedimentation monitoring study has serious repercussions in determining a navigator’s route map, especially when maneuvering in the Mactan Channel.

Navigators usually have a map of the shallow and deep portions of the channel but siltation, sedimentation and garbage in the sea bottom have changed the contours of the seabed.

In recent years, navigators have experienced difficulty in maneuvering in the Mactan Channel because of congestion and a seemingly chaotic vessel traffic management system.

Heavy siltation and the decreasing depth of the channel could make ships vulnerable to grounding and if left unchecked, will make the waterway impassable in time. — Freeman News Service