HYDROLOGICAL AND EROSIONAL ENVIRONMENT INFERRED FROM CHANGES IN TREE RING WIDTH AND GRAIN-SIZE OF POND SEDIMENT

从山上两个地区采集的样本中分析了过去300-400年的树木年轮宽度。兵库县北部地区的Myoken-San表明，近90年来年降水量较大时，树轮宽度较小。通过对神户地区池塘沉积物的粒度分析表明，利用137Cs浓度可以从位于强降雨区域的池塘的粒度序列中追踪到多年的暴雨。这些年在暴雨区的粒度分布上表现出明显的粗化，而在非强降水的地区则没有明显的粗化。

Analyses of tree-ring widths that span the past 300-400 yr in samples taken from two areas in the Mt. Myoken-san in the northern area of Hyogo prefecture indicate that tree ring width was small when annual precipitation was large during past 90 years. This tendency was also seen in the age of pre-observatory from historical records ; there happened many floods when the ring width was comparatively small.Grain-size analysis of pond sediments in Kobe district shows that years of heavy rainfalls can be traced in the grain-size sequences from the ponds located in the heavy rainfall area by the use of 137Cs concentration. These years show up as prominent coarsenings in the grain-size distribution in the heavy rainfall area while there was no prominent coarsenings in the area of no heavy rainfall.