Effect of timber harvesting on stormflow characteristics in headwater streams of managed, forested watersheds in the Upper Gulf Coastal Plain in Mississippi

Headwater streams are crucial parts of overall watershed dynamics because they comprise more than 50-80% of stream networks and watershed land areas. This study addressed the influence of headwater areas (ephemeral and intermittent) on stormflow characteristics following harvest within three first-order catch- ments in the Upper Gulf Coastal Plain of Mississippi. Four treatments including two Best Management Practices (BMPs) were applied: BMP1 - removal of all merchantable stems while leaving understory intact with minimum surface soil disturbance; BMP2 - same as BMP1 with the addition of logging debris to the drain- age channel; Clearcut - total harvest with no BMPs applied; Reference - left uncut as a control. Following harvesting, the increase in water table depth ranged from 1.6 cm in BMP1 to 28.2 cm in the clearcut treat- ment during 2008, and from 10.5 cm in BMP1 to 54.2 cm in BMP2 during 2009. However, impacts of timber harvesting on peak discharge, storm discharge, and time of concentration were not consistent with water table response. Response time to stormflow was reduced significantly in harvested treatments (BMP2 and unre- stricted harvest) probably as a result of decreased evapotranspiration and increased soil disturbance.