Assessing the influence of drainage pipe removal on wetland hydrology restoration: A case study

Abstract

In this study, we assessed the restoration of a riparian wetland in a moderately incised glacial till valley of the Midwest where drainage pipes were either removed or disabled in 2000 and 2004. The study determined whether wetland hydrology was restored at the site and whether former drainage pipe locations still influenced wetland hydrology after restoration ended. Water table level measurements in 2004 and 2005 indicate that wetland hydrology has been restored in areas of the riparian zone with poorly drained loamy soil. These areas are characterized by an average water table depth of 10 cm below ground surface (BGS) for approximately six months of the year and a water level above 30 cm BGS for at least 4 consecutive days during the growing season. High-resolution water table measurements during and after precipitation events did not indicate that former drainage pipe locations affect the hydrology of the site either by allowing a quick water table drawdown or by acting as preferential conduits for groundwater during precipitation events. Overall, data indicate that wetland hydrology was restored and that the technique of cutting the drainage pipes into several sections or removing them by hand and compacting the disturbed soil back into place without adding any extra material was an appropriate restoration technique for this site. ©2008 by the Board of Regents of the University of Wisconsin System.