Firefighters patrol downtown Davenport, Iowa, in a boat as floodwaters from the Mississippi River continued to rise yesterday.National Guard troops worked to shore up water-logged levees on Monday as forecasters said the Mississippi River, out of its banks in four northern states, would become even more dangerous with new rainfall.That flood caused more than US$100 million damage in Davenport but the city elected not to build a permanent flood wall, preferring to keep access to the river open and scenic.Agencies via Xinhua