Alteration of soil hydraulic properties during the construction of mitigation wetlands in the Virginia Piedmont

Wetland hydrology is a critical component to the success of mitigation projects. The alteration of soil hydraulic properties during the construction may influence the hydrology of the wetland, thus affecting the mitigation success. We studied disturbed (i.e. by construction) and nondisturbed areas of two wetland mitigation banks (Blackjack, BJ and Peters Farm, PF), both located in the piedmont region of Virginia, for a variety of soil hydraulic and physicochemical properties. The surface soil horizon at BJ showed an increase in clay content from 18.6 to 40%, decrease in bulk density (Db) from 1.56 to 1.45 g/cm3, decrease the drained volume (Dv) of water in the soil profile from 0.67 to 0.36 cm, decrease in available water content (AWC) from 22.7 to 15.8%, and a reduction in the ratio of AWC to TPS from 66 to 40%. Soil at PF showed an increase in clay content in the surface horizon from 20 to 30%, increase TPS from 37.2 to 40.0%, increase Db from 1.52 to 1.67 g/cm3, increase the Dv in the soil profile from 3.5 to 6.6 cm, increase in AWC from 37.2 to 40.2%, and a decrease in the ratio of AWC to TPS from 58 to 44% in the surface horizon. The outcome showed that the impacts of common construction practices for mitigation wetlands affected drainable and plant available subsurface water storage, more so in fine grained soils. Key soil hydraulic properties should be considered in the disturbed or ameliorated state before water budgets are constructed to model wetland hydrology. Further studies are needed to investigate how the plant available and drainable water contents can be affected by construction practices in various soil textures, and how these properties might change in the long term.