An Analytic investigation of periglacial topography in Horonobe region, Hokkaido

Hanatani, Ikuo; Munakata, Masahiro ; Kimura, Hideo; Sanga, Tomoji*

We conducted a study on key factors regarding changes of groundwater flow from the last glacial to the postglacial stages in the Horonobe. Specifically, geomorphological analysis was carried out using aerial photographs and a high resolution (10 m) DEM to obtain the distribution of the slopes that had been formed after the last glacial stage, and the erosion depth of those slopes was analyzed. The results are summarized as follows: (1) Although periglacial smooth slopes which expanded widely in Horonobe region over the last glacial stage were eroded by rainfall increase and steeper slopes had been formed in the postglacial stage, this postglacial erosion is not uniform and is strongly influenced by the geology. (2) The drainage density is low and less than 40% of periglacial smooth slopes have been eroded to the present in the Koetoi and Wakkanai Formations while it is high and 60% or more of those slopes have already been eroded in the Yuchi and Sarabetsu Formations.