Bangkok is sinking an average of 10mm per year and the subsidence, or downward shift, could reach critical levels unless the problem is tackled immediately, a leading water engineer warned the National Reform Council on Thursday.
Groundwater extraction, the natural movements of the Earth’s crust and construction of high-rise buildings were some of the factors causing Bangkok to sink, said Sujarit Khoonthanakulwong, head of Chulalongkorn University’s water resources engineering department at a seminar on Thursday.
Ramkhamhaeng Road is sinking the fastest of any urban area, at 2cm per year, followed by Lat Krabang at 1cm, according to Mr Sujarit. On average, the capital and its surrounding areas are dropping towards sea level by about 10mm annually.
Coastal areas in nearby Samut Sakhon and Samut Prakan provinces are also eroding, Mr Sujarit said, adding that unless relevant laws are strictly enforced, Bangkok would be at high risk of being flooded in 30-50 years.
He suggested that national reforms focus on amending zoning laws for water retention and city planning. Penalties must be increased for illegal use of groundwater, he said.
Meanwhile, the Bangkok Metropolitan Administration (BMA) says it already has measures in place to deal with the problem, according to Sornchai Tovanichakul, the director of analysis and research with the BMA public works department.
Safeguards include controls on housing construction and buildings no more than 12m high in areas prone to flooding, Mr Sornchai said.
Parts of building construction areas must be set aside to retain water until it can be released into waterways, he added.
The BMA says it has already dredged water drainage canals, built flood embankments along the Chao Phraya River, constructed seven giant flood tunnels and set aside 26 areas as flood-retention areas.
Bamboo walls were built along natural coastlines to prevent further erosion and trees were planted in mangrove forest areas, according to Mr Sornchai.