Abstract
In order to find out the process of gully development and to examine it's possible contribution to sediment yield, field test of soil erosion was carried out under splinkling using rain guns and the subsequent rainfalls.
The test plot was 5m wide and 40m long in the direction of slope, set on a bare and flat dry field (slope: 7°) which had been reclaimed from hill. During two splinkling runs, the first step of gully advancement was observed and flow velocities were measured. For 3 months there after, any changes on land surface were surveyed periodically at the intersecting points of 1m×2m-mesh in the test plot, as well as the longitudinal traces of gully bottom.
At the first step of gully development, there were many pairs of short gully and sediment fan just downstream. Thereafter, short gullies were connected with those upstream, passing through the sediment fan just above.Through out the process, each gully advanced widening and deepening without restriction by hard subsoil.Slope of the gully bottom decreased gradually from upstream to downstream fan.
Mean change on land surface except for gully decreased to zero in a short time and as a result, the greater part of sediment yield was from gullies.
In this paper, note that the term of “gully” was used for all theclear cut depressions on land surface and that of “sediment yield” for the volumetric soil loss out of the test plot.
