Anabranch

An anabranch is a section of a river or stream that diverts from the main channel or stem of the watercourse and rejoins the main stem downstream. Local anabranches can be the result of small islands in the watercourse. In larger anabranches, the flow can diverge for a distance of several or even hundreds of kilometers before rejoining the main channel. The term anabranch, in its hydrological meaning, is used more frequently in Australia than in the rest of the English-speaking world. The term anabranching river describes a river with many anabranches, whilst an anastomosing river is an organic-rich subset of this river type. The term braided river describes watercourses which are divided by small islands into multiple channel threads within a single main channel, but the term does not describe the multiple channels of an anabranching river. A distributary is a branch of a river that does not rejoin the main channel; these are common on and near river deltas. A bayou is often an anabranch. An anabranch that gets cut off from the main channel becomes an oxbow lake, known in Australia as a billabong. The Magdalena River, in Colombia, bifurcates in El Banco in two branches: Brazo de Loba (Shewolf Branch in Spanish) and Brazo de Mompox. The first one, Brazo de Loba is the main navigable channel and is 177 km long. Brazo de Mompox is thus the anabranch. There are several other branches that join those two main branches, interconnected by swamps ("ciénagas"), the main ones being Quitasol, Chicagua and La Victoria. Between Brazo de Loba and Brazo de Mompox is the island of Mompox or Margarita Island, a sunken geological block of 2.200 square km between the faults of Chicagua and El Romeral. In the Fraser River delta of British Columbia, Canada, North Arm Fraser River, Middle Arm Fraser River, and South Arm Fraser River each fall into Georgia Strait separately. On the other hand, Annacis Island splits (South Arm) Fraser River into the (main) Annieville Channel and the (smaller) Annacis Channel, which rejoin below the island.