New technology is helping to protect Hong Kong’s extensive shoreline with the city facing more extreme weather in the coming years, government engineers say.
The carnage wrought last year by Typhoon Mangkhut, the most intense storm in the city’s recorded history, has led the administration to step up its use of cutting-edge imaging techniques for inspections of piers, sea walls, breakwaters and typhoon shelters.
The potential for disaster was revealed when a sea wall collapsed during the September 2018 storm, allowing sewage waste to leak into the sea from Sai Kung, in the east of the New Territories.
“Due to the emergency in the Sai Kung sewage plant, we applied the new technologies to inspect the damage of the sea wall,” Angus Yip Wai-ho, a senior engineer at the government’s Civil Engineering and Development Department (CEDD), told a media briefing.
“It might not have been possible to send a diver to inspect due to the weather conditions. So I believe the new technology has greatly improved our efficiency.”
Lawmakers in the city were warned in May that global warming and rising sea levels meant Hong Kong was exposed to typhoons even more damaging than Mangkhut in the future.
The city has a shoreline spanning 1,100km (683.5 miles), of which 16 per cent is made up of man-made structures.
Responding to the ongoing threat of extreme weather events, surveyors recently started to used a new integrated system scanner.
It uses laser imaging to capture the state of the facilities above the water and sonar waves to detect underwater structures, producing a high quality three-dimensional model for inspection.
Without the scanners, divers would have to swim in the dirty seawater for several days to map out where to make repairs.
“Many factors such as water traffic, tidal waves and poor water quality made the operations very difficult and produced unclear images,” said Alan Tang Kai-yan, chief engineer of the CEDD’s port works division, at last Thursday’s briefing.
“These new devices can reduce the working condition risks faced by divers.”
The integrated system scanner and imaging sonar device, which cost about HK$3 million (US$380,000), has been in use since the middle of last year, and with increasing frequency since Mangkhut.
The department expects to complete a full inspection of Hong Kong’s 127km of sea walls and breakwaters every five years, using the scanner system.
Another imaging sonar device can take high-resolution videos and pictures of underwater beams, which connect pier docks to the seabed.
It would be used in routine checks of the 318 piers and landing steps in the city, which were used by about 46 million passengers in 2018. The device would shorten the inspection time to just an hour.
The CEDD will also pilot the use of drones to scan the narrow space beneath the pier dock and just above the water surface.
That would forgo the need to build a temporary work platform for that purpose, which would cost several hundred thousands of dollars and could take months to inspect a single pier.
Mangkhut struck the city on September 16 last year and was confirmed by the Hong Kong Observatory as the most powerful storm to hit these shores since records began in 1946.