![]() The Rakaia River has eroded a channel up to one hundred meters deep into the Canterbury Plain. Braided river channels can flow within an entire valley floor or in an area defined by stable banks. Channel formation changes regularly, most significantly during major floods. Channels and braid bars within a braided river system are highly mobile (Figure 2). Braided streams are most common wherever drastic reduction in stream gradient causes the rapid deposition of a streams sediment load. Compared to other types of river formations, braided rivers are more complex and less easy to understand, unlike a system such as a meandering river system. Braided river channels are unique geographic features. A braided river system like the Rakaia is a river channel that consists of a network of small channels separated by sediment deposits known as braid bars. Finally is the focus on physical processes such as sedimentary and hydraulic conditions that begin the braiding process (Ashmore, 1991). Second is the formation of braids to theoretical stability analyses of channel bars in two dimensional flow regimes. First is a practical explanation relating the braiding to a combination of external forces, environmental factors such as discharge and the supply of sediment. There are three general categories as to the theories on the cause of braiding in alluvial systems. Location of the Rakaia River, shown inset of the South Island of New Zealand. Factors to sediment supply such as high sediment change in a natural glacial systems from the erosion of the earth’s surface due to abrasion caused by the advancement and retreat of a glacier.įigure 1. My final objective will be to explain braiding indexes, which are the levels of the degree of braiding in a system, and the glacial influence on sediment supply to a braided river system. Reasoning behind the most commonly accepted fact that what influence’s channel patterns of braided systems are the varying supply of water, sediment supply, and in short term, the factor of the slope of the channel. Once we know, what a braided system is we will go over the many external factors involved with braided streams. Explanation’s about what a braided river system is and what specific features it has and needs, to be considered a braided river system, reasons such as why most braided river systems are most commonly found wherever drastic reduction in stream gradient causes the rapid deposition of a streams sediment load. ![]() ![]() Through this paper, I am going to go explain the processes that form a braided stream system. The Rakaia River, which has a mean annual flow of two hundred and three cubic meters per second, is mainly a braided river system it becomes briefly confined in a narrow canyon known as the Rakaia Gorge roughly sixty-one kilometers from the east coast of the South Island. Many of these studies are conducted at the headwaters of the systems, where features such as large glaciers form high in the mountains producing the mass amounts of water and sediment that feed braided streams such as the Rakaia.įorming out of the glaciers of the Southern Alps and flowing easterly one hundred and fifty kilometers across the Canterbury Plains on the South Island of New Zealand and entering into the Pacific Ocean approximately fifty kilometers south of Christchurch, New Zealand is the Rakaia River (Figure 1). Most research conducted on braided rivers such as the Rakaia River has been done within the last one hundred years, with most of the advances coming in the last thirty years due to more studies on various different rivers and the beginning process of braided streams along with the increase in the level of technology. Much is known about these systems with many studies still being conducted to find more information about these amazing river systems. This paper is written to provide an overview of the mechanisms that drive the formation and causes of braided river patterns, specifically the Rakaia River located on the South Island of New Zealand. Studies being conducted on various braided river systems around the world are always coming up with new evidence as to why these unique river systems form and what factors influence their formation. Outside Factors Dealing with Stream Braiding 4īraided river systems are some of geography’s most unique land features. Fluvial Processes of Braided Streams: Rakaia River, South Island New Zealand
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