Issues with a lake for Christchurch

I blogged how Sir Bob Jones had proposed a lake in the Chch CBD, with businesses being allocated a shorefront location. At the time I said I liked the proposal, but wasn’t sure it was practical.

A reader e-mailed his brother who is a geological engineer. He commented:

In an area that is prone to liquefaction the last thing you want is have more ponded water in the form of a lake.  Lake edges are typically worst affected by lateral spreading induced by liquefaction, often 10s to 100s m back from the ponded water. To create an artificial lake in the Chch CBD you would have to dig a large hole in the ground to hold the water.  This allows the surrounding lake shore and adjacent land to move (expand) under strong earthquake shaking – to spread laterally into the lake. But If the ground is still in place you get a lot of cracking and water and silt ejection, but not much ground deformation.  Its the ground spreading, often accompanied by subsidence, that is most damaging to buildings.  The best way to stop this from happening is to lower the general ground water table, and create a ‘non-building buffer zone’ (of land) along the banks of rivers, canals, and around the shores of other bodies of water bodies  – not dig more holes in the ground and fill them with water !!

So sadly not practical.