Natural restoration basics for wetlands

Around the world, dams, diversions, and drainage systems reengineer rivers for navigation, farming, and urban development, and this has caused vast changes in the environmental conditions of the flood plains adjacent to these rivers (Middleton, 2002). Even though “flood pulses,” the periodic overflow of these rivers, were once the most important hydrological factor regulating all functions of the flood plain (Junk and others, 1986), now they have been reduced or eliminated along many of the world’s waterways (Sparks and others, 1998). These changes in river channels have created a hydrologic setting on flood plains that has not been conducive to restoration and nature conservation (Middleton, 2002). Consequently, USGS scientists are studying the long-term effects of hydrologic changes on flood plains, such as how the restoration of baldcypress (Taxodium distichum) swamps has been hindered because seeds cannot disperse or germinate without the seasonally driven high and low water levels associated with the flood pulse.