Introduction to Hydraulics: elementary lesson for students

金沢大学大学院自然科学研究

Advanced Java-based application to process thermoluminescence digital color images

Dielectric minerals that interact with ionizing radiation emit thermoluminescence when heated. The color of the emitted thermoluminescence varies among different samples, even for the same minerals. TL color analysis can be used to study mineral provenance. Thermoluminescence color images (TLCI) can be obtained using a digital camera. Inagaki et al. (2010) created a Java application to handle RGB (red-green-blue) information of each pixel. This Java application is able to visually represent thermoluminescence color on a CIE (Commission Internationale de l’Eclairage) chromaticity diagram. Here, we report an improved Java application that enables the numerical treatment of TLCI of various image sizes and resolutions. This application allows for the handling of many digital TLCI in a short time and it is useful for statistical color analyses

Mobility and Location of Drainage Divides Affected by Tilting Uplift in Sado Island, Japan

Drainage divide is a dynamic feature that migrates in response to tectonic activity. The asymmetric uplift between two adjacent basins causes the divide migration from a slower to faster uplift area. Sado Island, Japan, has been affected by southeastward tilting uplift for ca. 300k years. Despite the faster uplift on the northwest, the main divides have existed on the southeast side of the geometric center of the island, with no other feature suggesting tectonic inversion of the tilting direction. In this study, we conducted a digital elevation model (DEM) based investigation that focused on divide migration. A spectrum from very inactive to active divide migration in the northwest. Regardless of their position, actively migrating divides are comprehensible, but inactive divides located in a relatively slow uplift area remain unclear. We concluded that some divides slowed down owing to the local balance of erosion rates across the divides, which does not imply balance between uplift and river erosion at the basin scale, reflecting disequilibrium in river longitudinal profiles. The main divides of Sado have presumably continued to slowly migrate toward the area of faster uplift; however, they are most likely to have never overcome the moving geometric center owing to land expansion at the seacoast due to asymmetric uplift

Mobility and Location of Drainage Divides Affected by Tilting Uplift in Sado Island, Japan

Drainage divide is a dynamic feature that migrates in response to tectonic activity. The asymmetric uplift between two adjacent basins causes the divide migration from a slower to faster uplift area. Sado Island, Japan, has been affected by southeastward tilting uplift for ca. 300k years. Despite the faster uplift on the northwest, the main divides have existed on the southeast side of the geometric center of the island, with no other feature suggesting tectonic inversion of the tilting direction. In this study, we conducted a digital elevation model (DEM) based investigation that focused on divide migration. A spectrum from very inactive to active divide migration in the northwest. Regardless of their position, actively migrating divides are comprehensible, but inactive divides located in a relatively slow uplift area remain unclear. We concluded that some divides slowed down owing to the local balance of erosion rates across the divides, which does not imply balance between uplift and river erosion at the basin scale, reflecting disequilibrium in river longitudinal profiles. The main divides of Sado have presumably continued to slowly migrate toward the area of faster uplift; however, they are most likely to have never overcome the moving geometric center owing to land expansion at the seacoast due to asymmetric uplift

地殻変動の様式変化による山地河川発達への影響: 室内モデル実験と力学的理解

金沢大学理工研究域地球社会基盤学系地殻変動の影響を強く受ける山岳河川の発達過程に関しては、平野に発達する沖積河川と比べて理解が遅れている。そこで、山岳河川の室内モデル実験を行った。（１）中流域のみが隆起する場合と（２）流域全体が傾動隆起（陸側が海側より速く隆起）について行い、以下のことが分かった。（１）隆起地帯を河川が流れ続けるか、流路放棄が生じるかは、下刻（河川が河床を下方に削る）速度と隆起速度の大小関係のみで決まるような単純なものではなく、周辺の流路パターンの変化に支配される複雑なメカニズムによる。（２）本流と支流の縦断形発達の時間的なずれが、隆起がない場合に比べて小さくなる。Developmental processes of mountainous rivers has not been well understood in comparison to alluvial rivers on plains. In this study, laboratory (model) experiments were conducted under two types of uplift: (1) uplift only in a midstream area and (2) tilting uplift over the whole basin (uplift rate increases landward). Under (1), whether the stream continues to flow inside the uplift area or abandons the uplift area is not determined only by the balance between incision and uplift rates, but controlled by complex reaction due to change in channel networks in surrounding areas. Under (2), difference between timings of long-profile development of a trunk channel and tributaries is unclear in comparison to the case of no uplift.研究課題/領域番号: 25350424, 研究期間(年度):2013-04-01 - 2017-03-3

海底河川のチャネル発達過程・堆積構造と環境パラメーターに関する水理実験

金沢大学理工研究域昨年度、開発・検討を行った小型平面模型を用いて、チャネル・パターンの発達実験を行なった。流れの供給様式には、地上河川の場合、直接的な降雨水、流去水、地下水の3つの成分に分けられる。いずれも、ひとつの流域内で地域差を持ち、河川地形に大きく寄与するポテンシャルを持っている。一方、海底チャネルの場合は、一般的には専ら密度流のみが地形に寄与すると考えられる。そもそも地上河川について、流水の3つの成分のそれぞれがどのように地形発達に寄与するかは不明な点が多い。自然の地上河川を見る限りでは、これら3つの成分を合わせた結果しか知ることが出来ない。乾燥地帯を流れる河川については、降雨水の成分を除いた場合になるし、源流も乾燥地であるなら流去水の成分も除かれるが、自然は複雑で、岩質、植生など多くのパラメータを含み、地下水だけの影響を議論するのは難しい。そこで、流水が地下水(浸透水)のみによるケースについて、チャネル発達実験を行った。結果、傾向としては、初期勾配が大きい程、チャネルは樹枝状になった。初期勾配が低いと蛇行、網状になりやすい。チャネルが全体として蛇行する場合でも、谷頭浸食は最大傾斜の方向にほぼ真っすぐ進む。チャネルは、初期の泉のわき出し点から上流、下流どちらにも延びるが、蛇行する部分は下流から上流へ伝搬し(蛇行そのものの連続的なシフトとは別)、最終的には初期のわき出し点よりも上流にまで及んだ。チャネルの最下流は河口であり、自然界では、上流からの流れだけでなく、波浪や潮流の影響を受ける。この場合、流向は時間変化する。流向変動がある場合の河床に発達する微地形について、貧砂状況時を想定した実験も行った。結果、三日月型地形(barchan)が特徴的な変形を受けることが分かった。この知見は、水成地形のみならず、風成地形にも適応可能であり、火星の砂丘についての考察にも応用できた。研究課題/領域番号:17740334, 研究期間(年度):2005 – 2006出典：「海底河川のチャネル発達過程・堆積構造と環境パラメーターに関する水理実験」研究成果報告書　課題番号17740334,（KAKEN：科学研究費助成事業データベース（国立情報学研究所））（https://kaken.nii.ac.jp/ja/grant/KAKENHI-PROJECT-17740334/)を加工して作

地形・地層発達過程のマルチスケール干渉現象: 流路発達モデル実験の時系列相関解析

小型平面水槽内で河川網のモデル地形を生じさせ、発達過程の特性を調べた。扇状地上の流路は時間的に遷移するが、遷移の仕方には時間経過に伴う履歴の影響が表れた。地層への応用面を考慮し、層厚分布に関する既存の確率モデルの逆問題を考察し、ある条件下で求解可能性を示した。本研究での確率モデルでは、堆積侵食量の発生確率分布は定常を仮定するが、今後は履歴効果を取り入れたモデルが求められる。By flume experiments, characteristics of the topological development of stream channels on fans were investigated. The effect of its history (hysteresis) was observed in migration and avulsion of channels. Besides, it was found that the inverse problem of Kolmogorov model dealing with layer thickness distribution could be solved under particular conditions. In this work, the constant probabilistic function of erosion and sedimentation amounts were assumed. A model that can well reproduce hysteresis is a future work