In China, this spring's unusually heavy rains killed more than 600 people in flash floods and mudslides. Officials are battling years of bad conservation practices to prevent worse flooding as the summer rainy season gets into full swing.
This year floods have caused more than $3 billion in damage and forced 1.4 million people to flee their homes. In a few areas, these are thought to be the worst floods in 500 years.
Richard Grove-Hills is the head of the East Asia office for the International Federation of Red Cross and Red Crescent Societies. He said summer rains bring some flooding to China every year, but normally not this early nor in the places being hard hit now. "This is a very different type of flooding than normally occurs in China," he said. "Normally, the traditional flood is along the Yangtze."
The Yangtze is China's biggest river, and it is reported to be dangerously high this summer.
The floods occur every few years, and have for centuries. In recent decades, however, the problem has worsened, as floods become not only more frequent, but larger and more damaging.
Part of the problem has been the gradual change in the world climate. But part of it has been China's mismanagement of its resources.
Over-logging has stripped away forests, which are needed to slow the movement of rainwater and help more of it sink into the ground, instead of filling rivers. Over-farming has eroded topsoil, which also traps water. Over-building has put houses and factories too close to rivers, so that floods do more damage to structures.
Ye Chen is a climate expert at the Chinese Academy of Sciences. He said China needs to change such practices to reduce the flood damage. "It is definitely true that human activity has an impact on the climate, but we also need to learn to live together with nature," he said.
The government has started to make some changes. China has banned logging in many areas and is expanding programs to plant trees and return reclaimed land to rivers and lakes.
Following disastrous 1998 floods that killed 4,000 people, China invested billions of dollars in flood-control projects. Officials hope that investment will pay off, by reducing the death toll this year.
This year, however, the worst floods have been in areas that normally see little rain. That means thousands of farmers tilling dry riverbeds and lowlands were caught by surprise as torrents of rain and mud swept away crops, livestock, and people.
Chinese officials say other people perished in mountainous areas when heavy rain brought mudslides crashing into homes and villages.
Mr. Grove-Hills with the Red Cross said the key question will be whether China's swollen rivers can handle the normal heavy summer rains over the next several weeks.
With that in mind, China's government is trying an experiment to increase the capacity of the rivers to handle floodwater.
Dams built for flood control have the unintended side effect of slowing down the speed of the water. That increases the amount of silt deposited on the river bottoms. With tons of silt deposited each year, rivers become shallower, hold less water, and become more flood-prone.
This year, the Yellow River Water Conservancy Commission is releasing huge quantities of water from a dam to speed the river flow and scour the silt out of the bottom.
Engineers are trying various flow rates to see what will clear out the silt without flooding cities along the river. Li Guoying is head of the Conservancy Commission. Mr. Li told state television that this is the world's biggest silt clearing program, and that controlling rampaging rivers has been a Chinese dream "for generations."
Fulfilling that dream, however, remains far off. Mr. Ye, the climate expert, said that to control the floods, China needs help from residents and officials, as well as scientists and engineers.