山地試験地における降雨流出の観測 ―落葉層からの流出―

Abstract

Intensity of rainfall (P) and that of runoff (Q) have been observed at a small testplot on a natural mountain slope since 1960. The intensity of runoff from the fallen-leaf layer is only about ~of P when P<300p/inin, but acceleratively increases whenP>300 p/mm. The one from both the fallen-leaf layer and humus layer is proportionalto P and equal to 0.1 P at least when P<600 fl/mm. Probably, the runoff from thefallen-leaf layer is caused by anisotropic transmission of rain water along surfaces offallen leaves, and when P>300 p/mm, a part of the runoff water from the humus layeris added to that from the fallen-leaf layer. Initial losi~ of rainfall becomes constant(2.5 mm) after a lapse of one day or more since the previous rain.