@article{oai:rekihaku.repo.nii.ac.jp:00001061,
 author = {斉藤, 亨治 and Saito, Kyoji},
 journal = {国立歴史民俗博物館研究報告, Bulletin of the National Museum of Japanese History},
 month = {Mar},
 note = {application/pdf, 善光寺平では，更新世前期からの盆地西縁部の断層の活動により盆地が形成され，その盆地が地殻変動・火山活動・気候変化によって盛んに供給された土砂によって埋積された。善光寺平周縁をはじめ長野県に扇状地が多いのは，流域全体のおおまかな傾斜を表す起伏比（起伏を最大辺長で割った値）が大きく，大きい礫が運搬されやすいためである。その扇状地には，主に土石流堆積物からなる急傾斜扇状地と，主に河流堆積物からなる緩傾斜扇状地の２種類ある。急勾配の土石流扇状地については，その形成機構が観測や実験によりかなり詳しく明らかになってきた。しかし，緩傾斜の網状流扇状地については，その形成機構はよく分かっていない。扇状地と気候条件との関係では，乾燥地域を除いて，降水量が多いほど，気温が低いほど，扇状地を形成する粗粒物質の供給が盛んで，扇状地が形成されやすいといえる。また，気候変化との関係では，日本では寒冷な最終氷期に多くの扇状地ができた。その後の温暖な完新世では，扇状地が形成される場所が少なくなったが，寒冷・湿潤な9000年前頃と3000年前頃，扇状地が比較的できやすい環境となっていた。善光寺平の地形と災害との関係では，犀川扇状地および氾濫原部分では，1847年の善光寺地震で洪水に襲われているが，氾濫原部分では通常の洪水もよく発生している。扇端まで下刻をうけた開析扇状地では水害が発生しにくいが，扇頂付近が下刻をうけ，扇端付近では土砂が堆積するような扇状地では，下刻域から堆積域に変わるインターセクション・ポイントより下流部分で水害が発生しやすい。裾花川扇状地や浅川扇状地には扇央部にインターセクション・ポイントがあり，それより下流部分では，比較的最近まで水害が発生していたものと思われる。, The basin of the Zenkoji Plain was formed in the early Pleistocene age by fault activity on the western fringe of the basin. The basin was buried in sediment supplied by active crustal movement, volcanic activity, and climatic changes. Nagano Prefecture has many alluvial fans, among them the fringes of the Zenkoji Plain, because large debris is easily moved owing to the large relief ratio (the value of relief divided by maximum basin length) seen on the broad slopes of the entire drainage basin. There are two types of alluvial fans. Steep alluvial fans are caused mainly by debris flow. The shallow sloped alluvial fans are caused mainly by stream flow. The formation process of steep debris-flow dominated fans has become clearly understood owing to measurements and experiments. However, the formation process of shallow sloped, stream-flow dominated fans is not well known. The relationship between alluvial fans and climate is that, with the exception of dry regions, the higher the amount of precipitation and the lower the temperature, the greater the supply of coarse material that forms alluvial fans will be. It can be said that alluvial fans form easily. Also, as for the relationship with climatic changes, many of Japan's alluvial fans were formed in the Last Glacial age. After that, in the warm Holocene age, there are fewer locations in which alluvial fans have formed. Approximately 3,000 and 9,000 years ago, in cold wet eras, it was comparatively easy for alluvial fans to form. The relationship between the topography of the Zenkoji Plain and natural disasters is that the Sai River alluvial fan and flood plain were covered by flooding caused by the Zenkoji earthquake of 1847. In addition, flooding occurs regularly in the flood plain. It is difficult for flood damage to occur in the dissected alluvial fan that has experienced downcutting at the toe of the fan. While in alluvial fans in which the fanhead area and down fan have experienced downcutting and deposition respectively, it is easy for flooding to occur downstream from the intersection point of downcutting area and deposition area. The intersection points are in the center of the Susobana and Asa river alluvial fans. It is thought that downstream from those points flooding occurred until comparatively recent times.},
 pages = {247--263},
 title = {善光寺平の扇状地と地形災害},
 volume = {96},
 year = {2002},
 yomi = {サイトウ, キョウジ}
}