Every year, Lower Mainland residents prepare for the Big One. The region is located near the Cascadia subduction zone, and it’s only a matter of time before a megathrust earthquake hits. During the annual Oct. 20 ShakeOut event in southwest B.C., school kids practice diving under desks. People ready their workplaces with emergency kits and evacuation plans. But there’s another type of disaster that we’re reminded about less often: a major flood.