Chch & Wgtn can benefit from UC research into Tokyo rivers

Christchurch and Wellington can benefit from UC research into Tokyo rivers

August 23, 2013

A University of Canterbury (UC) senior hazards lecturer researcher believes Christchurch and Wellington can benefit from his research on river channels in Japan.

Dr Christopher Gomez has been studying Tokyo’s rivers, which are seen as an accelerator of earthquake impacts in Japan’s biggest city.

``We are learning from the 2011 Japanese earthquakes and to see the areas of concerns relating to river channels. In 2010, half of the world’s population was living in cities and it has been projected that this ratio will rise up to 80 percent by the year 2050.

``It is very important we look at the environmental risks in cities. One place we could learn from is Tokyo, because of its population explosion in the aftermath of the World War 2, which makes it an excellent example of rapid urbanisation over coastal land.

``Tokyo, like Christchurch and the lowland areas of Wellington, is built by the sea on young sediments that have been deposited mostly by rivers or by the sea that has receded.

``As with Christchurch, most of the city of Tokyo was underwater only a couple of thousands years ago and most of its underground is composed of unconsolidated sediments that are ready to rock like jelly on a dinner plate.

``When rivers move laterally, they leave abandoned channels that are filled by fine and unconsolidated material. This unconsolidated sediment left in abandoned channels can dramatically increase ground acceleration during an earthquake, as observed in Christchurch in 2010 and 2011.

``There is a striking link between the amount of damage to buildings in central Christchurch and the location of abandoned and paleo-channel in the CBD area.

``Mapping of old river channels in Tokyo is a nightmare because of the incredible level of engineering that has been layered on the landscape and also because Tokyo is the convergence zone of the largest and most powerful rivers in Japan that have left a real geomorphological patchwork to decipher.

``The city’s expansion has rapidly engulfed different types of ground including abandoned channels, rice fields drained from marshlands and mine pits.’’

Dr Gomez will chair the geographical information system session at the International Conference of Geomorphology conference in Paris next week.

``It is a great honour because I will be the youngest chair at this conference, a privilege usually reserved for professors. It is a good opportunity to show the world the cutting edge research that we are doing at UC.

``It will be a chance to talk about the latest imagery, GIS and modelling techniques that we have developed at the Geography Department and the correlated research we are doing,’’ Dr Gomez says.

ENDS

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