HR: 08:45h
AN: H51J-04    [Abstracts]
TI: Hortonian Overland Flow in Humid Forested Environments: Occurrence, Measurement, Characterization, and Importance
AU: * Jackson, C R
EM: rjackson@forestry.uga.edu
AF: Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA 30602-2152, United States
AU: Schneier, J V
EM: joan.schneier@ncmail.net
AF: North Carolina DENR, 225 Green St (7th floor), Fayetteville, NC 28301-5043, United States
AB: Minimization, dispersal, and filtering of Hortonian overland flow is a main focus of forestry Best Management Practices. One of the several water quality functions of a forested riparian buffer is to filter surface runoff from upslope. However, few studies have quantified either the temporal frequency, spatial extent, or quantity of Horton overland flow from mature forests, clearcuts, or young plantations. As part of a multi-phase study of overland flow from silvicultural operations, we installed overland flow collector cups every 30 meters along the perimeter of streamside management zones of two clearcuts in the Georgia Piedmont, and we also installed overland flow collector cups along the imaginary SMZ boundary of a forested reference watershed. The cups were checked and emptied after every storm greater than 13 mm. Differentiating between Horton overland flow and saturated surface flow was difficult. Some responsive cups were clearly located in variable source areas as indicated by vegetation, soils, or the tendency of the cups to float, and other responsive cups were located in places where saturated surface flow would not be expected. For many responsive cups, however, differentiation between overland flow mechanisms was ambiguous. Since both saturated surface flow and Horton overland flow will concentrate due to topographic convergence, location cannot differentiate the flow mechanisms. Coincident measures of shallow groundwater are necessary to define surface flow generation mechanism. On all sites, the number of cups responding increased with the depth of the storm. The spatial distribution of responsive cups was only partly explained by topography. As expected, overland flow was common on the clearcut areas, and became less common over time as vegetation re-established. Overland flow was less common on the forested reference site, but still frequent and sometimes spatially extensive.
DE: 1806 Chemistry of fresh water
DE: 1815 Erosion
DE: 1826 Geomorphology: hillslope (1625)
DE: 1850 Overland flow
SC: Hydrology [H]
MN: 2007 Fall Meeting