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 14 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.

Hydrobiogeochemical Controls on Riparian Nutrient and Greenhouse Gas Dynamics: 10 Years Post‐Restoration

“…Previous work at the study site indicated that the hydrological restoration of the WL area was successful at reestablishing a hydro‐period consistent with WL environments in the WL area, namely a water table level within 30 cm of the ground surface for 5% of the growing season (USACE, ; Vidon and Smith, ). Over the study period, this criterion was met for all wells in the WL area, but not for wells in the AL area.…”

“…DOC concentrations reported here are consistent with redox patterns, as mean DOC concentrations in the WL and AL areas (5.29 mg/l) are within the range of those observed in groundwater in agricultural areas just a few miles upstream of the study site (3‐5 mg/l; Vidon and Smith, ; Vidon et al ., ). Typical DOC concentrations in WLs are often much higher (>15 mg/l; Mitchell et al ., , b).…”

“…Scott Starling Nature Sanctuary Location in Indiana, USA (a); Location of Wells, Piezometer and Static Chambers Nests (numbers 1 through 14) (b); General Soil Map (c); Historical Locations of the Subsurface Tile Drains Removed between 1999 and 2004 (d); Cross Section along Transect 1‐9 Showing the Dominant Soil Textures at the Site (L, loam; SL , sandy loam; S, sand; SG , sand and gravel) (e); Dotted Area Indicates the Location of the Restored Wetland Area at the Site Based on Vidon and Smith () (f). The two unlabeled dots near the stream indicate stream stage measurement points.…”

“…Finer textured soils (loam) near the hillslope (Figure ) correspond to the location of the WL area at the site. Sandy loam and gravelly sandy loam soils occur closer to the stream and correspond to the un‐restored AL area (Vidon and Smith, ). In the winter and spring seasons, dominant water inputs to the site are a combination of shallow hillslope water and seep water, while in summer these water contributions strongly diminish (Vidon and Smith, ).…”

“…Nonnative species were removed and native vegetation was planted each year between 1999 and 2004 to complete the restoration efforts. Between 2005 and 2006, two hydrological studies of the site were conducted (Vidon and Smith, , ) and confirmed that the hydrology of the WL area had been successfully restored according to the U.S. Army Corp of Engineer criterion for WL hydrology (i.e., water table within 30 cm of the ground surface for 5% of the growing season; USACE, ). In the restored area, vegetation consists of a mixture of various grass species interspersed with young trees.…”