Residents of earthquake- battered Christchurch were clearing up their flooded properties Wednesday after the city was hit by a once-in-a-century storm -- and scientists warned the quakes have only increased the incidence of floods. Roads and houses were flooded, communities cut off and schools closed on Wednesday in the wake of the fierce storm that lasted for 24 hours. River levels in Christchurch were dropping with the outgoing tide and as rainfall eased, but further rain was expected, Christchurch Mayor Lianne Dalziel said in a statement. Christchurch residents were urged to stay home if possible and to stay off the roads. About 4,000 homes were without power Wednesday. "This was a significant, escalating event that moved very quickly from a one-in-five-year event to a one-in-100-year event," said Dalziel. "The weather forecasts did not predict an event of this gravity. We were constantly reassessing the situation and managing it as needed." University of Canterbury researchers said Wednesday that Christchurch was experiencing more frequent and severe flooding due to the impact of the earthquakes that began in September 2010. Earthquake-induced "ground deformations," including liquefaction and subsidence, were posing an enhanced flooding threat, geography researcher Su Young Ko said in a statement. "One of the primary contributors to increased flooding hazards in Christchurch are the earthquakes which resulted in subsidence in some areas, narrowing of channels and uplifting of river beds," Ko said. Christchurch and the surrounding Canterbury region were shaken by a magnitude 7.1 earthquake on Sept. 4, 2010. A 6.3 magnitude quake on Feb. 22, 2011, killed 185 people and the city has been shaken by thousands of tremors since.