Increases in impervious cover can dramatically increase the size and frequency of localized flooding. Typically, urban floods are short-lived, but extended flooding can stress trees, leading to leaf yellowing, defoliation, and crown dieback. If damage is severe, mortality can occur. In addition, flooding can lead to secondary attacks by insect pests and diseases. Some species are more tolerant of flooding than others. Flood-intolerant species include upland species such as bitternut and shagbark hickory, Kentucky coffeetree, and white oak. Species that are generally tolerant of flooding include species that are generally native to wetlands and riparian areas such as baldcypress, sycamore, and red maple. Trees in coastal areas may also be vulnerable to saltwater intrusion during flood events.