A comparison of the hydrologic characteristics of natural and created mainstem floodplain wetlands in Pennsylvania

Abstract An understanding of wetland hydrology is critical for the assessment of the success of created wetlands relative to natural wetlands. Our objective was to determine if hydrologic characteristics differed between natural and created mainstem floodplain wetlands. We measured water depth every 6 h, between November 1, 1996 and August 31, 1998, and determined median depth to the water table, range of water table fluctuation, percent of time water was within the root zone (30 cm), and the number and duration of periods where water remained in the root zone. The natural wetlands were different from the created wetlands as median depth to water was generally deeper, there were shorter periods where soils were saturated or inundated, and there was a lower percentage of time where water was in the root zone. The created wetlands, in effect, were wetter and for longer periods. The created wetlands had a large component of open water at each site. Most naturally occurring mainstem floodplain wetlands in central Pennsylvania are vegetated with very little open water. We suggest that in the rush to make sure there is some water in mitigation wetlands we have gone too far in keeping sites inundated. In reality, many natural wetlands are merely saturated, or much drier.