High tides at full moon may cause floods

Muninggar Sri Saraswati, The Jakarta Post, Jakarta

While many associate a full moon with romance, this rainy season a full moon could also mean flooding.

The tides are high during full moon, which this month occurs on Oct. 31. It is also set to make an appearance on Nov. 30 and Dec. 29.

When the moon's gravitational pull reaches its peak, it drags the water on the earth's surface to its highest level.

Therefore everyone, but particularly those living near the sea, should be alert to possible flash floods when it rains hard during a full moon.

Rain started to fall last month, even though the official forecast from the Meteorology and Geophysics Agency said that the rainy season would not begin until the third week of this month.

According to the agency, the heaviest downpours will occur between January and February, 2002, when the full moon makes two further appearances, on Jan. 28 and Feb. 27.

Waan Tarmin, a spokesman for the agency, said flooding could be expected during the rainy season, since the city would have to accommodate an abundant amount of rainfall.

Waan was referring both to localized rains as well as to downpours in the upper courses of the Ciliwung and Cisadane rivers in the Bogor area.

Should heavy rains occur in the upper courses of the rivers, the waters will flow through some 13 rivers in the city, possibly resulting in floods here, even though it may not rain in Jakarta itself.

The agency predicts the amount of rainfall in northern parts of the city will range from 977 to 1,321 millimeters, and from 1,721 to 2,360 millimeters in the southern parts.

The amount of rainfall is relatively stable each year, according to data. The normal amount of rainfall is between 1,000 and 2000 millimeters.

Apart from high tides, other factors causing floods in the city are the poor state of the drainage system and the dwindling of water catchment areas.

"The city administration fails to maintain the drainage system here, which is mostly damaged or loaded with waste," he said.

"The drainage system plays an important role in preventing flooding since each year the city receives a similar amount of rain," he said.

Another reason for the city's vulnerability to floods is the fact that around 40 percent of the capital lies below sea level.

In the past few weeks, floods have hit several areas, particularly in East and North Jakarta, while many streets across the city have been inundated by water following heavy rains.

However, there are some areas near the sea, such as Jl. Gunung Sahari in North Jakarta, which are always hit by floods during a full moon, even during the dry season, Waan said.

"Flooding occasionally happens there even in the dry season, because of the weak drainage system.

In fact, even the heaviest rains would not cause flooding if the drainage system worked," Waan remarked.

Waan said the administration had also failed to maintain green areas in the city and its surroundings, which should be utilized as water catchment areas.