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<br />8 <br /> <br />concentration eventually causes catastrophic erosion of portions of the flood . <br />plain which Nanson termed "floodplain stripping." Eroded areas then begin a <br />new cycle of ve.rtical accretion. He argued that the presence of these eroded <br />areas leaves floodplains in a state of disequilibrium, meaning that the flows <br />required to inundate vertically accreting deposits are not well correlated in the <br />downstream direction. <br />Both Graf (1978) and Andrews (1986) describe channel narrowing along <br />the Green River in Utah. However, these authors disagree about the timing and <br />the cause, of this change. Graf (1978) matched photographs and concluded <br />. that there has been little change to the channel since 1962. He suggested that <br />narrowing occurred prior to dam construction (pre-1962) and this narrowing was <br />. caused by the invasion of saltcedar. <br />The work of Andrews (1986) offers a different interpretation. Andrews <br />used a sediment budget approach and suggested that the channel near Green <br />River, Utah, was accumulating sediment and narrowing in response to the <br />operation of Flaming Gorge Dam. He also concluded that the channel was still <br />adjusting to the change in flow regime and sediment transport caused by dam <br />operations and it might continue to narrow for many years. Neither the causal <br />mechanism for the channel adjustments nor the timing of those adjustments <br />were clearly identified by either researcher. <br />