財城 真寿美

1．はじめに <br>古代における人類の文化や生活に関わるさまざまな環境要因のうち，地形は住居立地や人流・物流などに直接的に関与する要素であり，たとえば遺跡分布と地形との空間定量的な評価は古代における文化変容を考慮する上で重要な課題として挙げられる。一方，海外調査や遠隔地における調査では，現地の詳細で正確な地形図は容易に得られるないことも多く，その場合は地理学的な現地調査を地形測量から行う必要がある。近年，レーザ測量器や写真測量の技術革新により，高精細な地形情報を研究者自ら，現場で迅速に取得することが可能となり，その適用が地考古学の分野でも進んでいる。本研究では，トルコ中部カイセリ県の遺跡周辺域を例に，高精細地形情報の取得と解析を実施し，地形分類や古環境復元に向けた基盤情報整備の有効性を示す。 <br> 2．対象地域と手法 <br>アナトリア高原中部に位置するカイセリ県北部には，前期青銅器時代からローマ時代にかけての古代遺跡が多数分布している。これらの遺跡とその周辺における地形・地物を対象とし，中でもとくに遺跡の立地する扇状地や，近隣の断層，岩屑なだれ堆積物など，特徴的な領域に着目して現地調査を実施した。その高精細地形情報の取得は，高解像度衛星画像のほかに，現地におけるレーザ測量，SfM多視点写真測量（Structure-from-Motion Multi-view Stereo Photogrammetry），GNSS（Global Navigation Satellite System）測量といった手法を用いて行った。写真測量のための画像取得には，ハンドヘルドカメラやsUAV（small  Unmanned Aerial Vehicle）に搭載した単焦点小型カメラ等を用いた。これらにより得られた3次元情報をもつ点群データを地理座標系に投影し，DEM（Digital Elevation Model）を生成するとともに，sUAVによる画像から得られたオルソ補正画像をあわせて，地形条件や遺跡立地条件などの空間解析を行うための基盤情報とした。<br> 3．結果と考察 <br>対象とした領域の範囲（数10 m〜数100 m）で得られた地形・地物情報の解像度は，数 m から数 cm のオーダーであり（図1），精細な地形・地物情報を判読，解析することが可能である。これらを精査し，対象地における地形判読・分類等を行う上での本研究における手法の有効性が示された。今後，こうした高精細地形・地物情報の取得・解析を進め，対象地における古環境と文化変容との空間関係を明らかにすることがさらなる課題として挙げられる．

In the present study, we estimated the July maximum temperature variations from 1830 to 2011 in the town of Kawanishi in the southern part of Yamagata prefecture using daily weather reports and observa tions documented in an old personal diary. Using historical weather reports, we computed the number of "fine-weather" days for each July during the study period. Then, July maximum temperatures in Kawanishi were estimated using a simple linear regression analysis based on the relationship between the July maximum temperature and number of "fine-weather" days, computed from historical weather reports. By com paring the time series of estimated temperatures with those of historical instrumental temperature data in the late 19th century, we found that the variation in the estimated temperature correlated well with that of the instrumental temperature data. This indicates that the estimated results in the present study are highly reliable. The results of this analysis showed that there were cool periods in the 1830s, 1860s, 1900s, and a period extending from the 1980s to the early 1990s. Those cool periods in the 1830s, 1860s, and 1900s coincided with poor rice harvests and severe famines in northern Japan. Warm summers were observed in the 1850s, a period extending from the 1870s to 1880s, and 1920s. We found that temperatures in the early 1850s were similar to those of warm summers in the late 20th century.

Rapid geomorphological changes mainly due to fluvial processes have been uccurring in Bangladesh despite its very flat topography. This observation reflects its location in the downstream areas of the two large rivers: Ganges and Brahmaputra, with their upstream areas being subjected to abundant rainfall. Fluvial systems in Bangladesh are quite complex, because the meandering Ganges and the braided Brahmaputra merges in the center of the country, and southern plains are prone to tide-related processes. Despite such interesting geomorphological settings, detailed scientific studies on landforms and sediments in Bangladesh have only been activated since the 1990s, because of political chaos in the earlier decades and a limited number of researchers within the country. It is necessary to extend recent studies to better understand the geomorphology of the country. This paper reviews the history and contents of geomorphological and geological studies for Bangladesh, to facilitate future progress of relevant research. Although this paper intends to cover a wide range of topics, special attention is directed toward fluvial geomorphology in relation to frequent large floods, which significantly affect people's life in Bangladesh.