River system

Japanese: 河系 - かけい（英語表記）river system

A river system consisting of the main stream and all the tributaries that flow into it. Almost synonymous with a river system. A river system develops in a sequence, including an initiation stage in which only fragmentary flow occurs due to slight unevenness on the ground surface, an extensional stage in which the river lengthens due to head erosion, a carving stage in which erosion progresses and the number of tributaries increases, a full expansion stage in which the river density on the ground surface reaches its maximum, and a complex stage in which the lower parts of the tributaries are absorbed by the erosion of the main stream and the river density decreases. The planar pattern drawn by a part or the whole of a river system is called a river system pattern, and is classified into several types. Dendritic means that the main stream and tributaries of a river take an indefinite direction, forming a tree-like shape as a whole. A variation of this is feathery. Parallel means that the main stream and tributaries flow parallel to each other for a considerable distance. Grid pattern means that the main stream and tributaries are almost parallel and are connected by short channels perpendicular to them. Radial means that the streams flow radially outward, as seen in cone-shaped volcanoes. Centripetal is when tributaries converge toward the center, as seen in a simple basin. Circular is when the main stream or some of the tributaries are arranged in a circular shape. Disordered is when the streams are connected in an irregular mesh pattern.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

川の本流とそれに注ぐすべての支流を合せた川の一系統。水系とほぼ同義。河系の発達には順序があり，初めは地表のわずかな凹凸に起因して断片的な流れがあるにすぎない開始期，頭部浸食によって川が延長していく伸張期，さらに浸食が進行して支流が増加する彫琢 (ちょうたく) 期，地表の河川密度が最大に達する満拡張期，その後支流の下部が本流の浸食によって吸収され河川密度が減少する複合期などがある。河系の一部または全体が描く平面形の模様を河系模様といい，いくつかのタイプに分類される。樹枝状とは川の本支流が不定の方向をとり，全体として樹枝のような形をなすもの。この変形として羽毛状がある。平行状とはかなりの距離にわたり本支流が平行して流れるもの。格子状とはほぼ平行する本流と支流とがそれらに直交する短い流路で結ばれるもの。放射状とは円錐形火山にみられるように外側に向って放射状に流れるもの。求心状とは単純な形の盆地にみられるように中心に向って支流が集るもの。環状とは本流または一部の支流が環状に配列するもの。乱網状とは不規則な網目状に連なるもの。

出典　ブリタニカ国際大百科事典小項目事典ブリタニカ国際大百科事典小項目事典について　情報

<<: Flower Whale - Shadow

>>: Flower stalk - Kakei