MITIGATING IMPACTS OF NEW FOREST ACCESS ROADS ON WATER LEVELS IN FORESTED WETLANDS: ARE CROSS-DRAINS ENOUGH?

Abstract

New forest access roads are routinely constructed across sections of forested wetland in Canada’s maritime provinces. Seven such roads in southwestern Nova Scotia and central New Brunswick were examined. Treatments of 20 m and 40 m culvert spacing were used to determine which spacing would best maintain natural wetland hydrology under the road after construction. Water table depths on both sides of each road were measured, with shallow wells, before and after the road was constructed. In six of seven sites, the part of the wetland upslope from the road had a significantly higher water table than the adjacent wetland downslope, after right-of-way clearing (before road construction). This condition continued after road construction regardless of treatment. These results suggest that natural wetland hydrology had been altered during right-of-way clearing and that alternative approaches to right-of-way clearing seem warranted to maintain natural wetland hydrology. In addition, further testing of culvert installation or other methods to maintain natural hydrology under roads through wetlands is needed.