The lower Green River episodically narrowed between the mid-1930s and present day through deposition of new floodplains within a wider channel that had been established and/or maintained during the early twentieth century pluvial period. Comparison of air photos spanning a 74-yr period (1940–2014) and covering a 61 km study area shows that the channel narrowed by 12% from 138 ± 3.4 m to 122 ± 2.1 m. Stratigraphic and sedimentologic analysis and tree ring dating of a floodplain trench corroborates the air photo analysis and suggests that the initial phase of floodplain formation began by the mid-1930s, approximately the same time that the flow regime decreased in total annual and peak annual flow. Tamarisk, a nonnative shrub, began to establish in the 1930s as well. Narrowing from the 1940s to the mid-1980s was insignificant, because floodplain formation was approximately matched by bank erosion. Air photo analysis demonstrates that the most significant episode of narrowing was underway by the late 1980s, and analysis of the trench shows that floodplain formation had begun in the mid-1980s during a multi-year period of low peak annual flow. Air photo analysis shows that mean channel width decreased by ∼7% between 1993 and 2009. A new phase of narrowing may have begun in 2003, based on evidence in the trench. Comparison of field surveys made in 1998 and 2015 in an 8.5 km reach near Fort Bottom suggests that narrowing continues and demonstrates that new floodplain formation has been a very small proportion of the total annual fine sediment flux of the Green River. Vertical accretion of new floodplains near Fort Bottom averaged 2.4 m between 1998 and 2015 but only accounted for ∼1.5% of the estimated fine sediment flux during that period. Flood control by Flaming Gorge Dam after 1962 significantly influenced flow regime, reducing the magnitude of the annual snowmelt flood and increasing the magnitude of base flows. Though narrowing was initiated by changes in flow regime, native and nonnative riparian vegetation promoted floodplain formation and channel narrowing especially through establishment on channel bars and incipient floodplains during years of small annual floods.

中文翻译：

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犹他州峡谷地地区的格林河下游因洪泛平原形成而使河道变窄

格林河下游在1930年代中期到今天之间，由于新的洪泛区沉积在一个较宽的河道中而逐渐缩小，该河道是在20世纪初的干旱时期建立和/或维持的。比较74年间（1940年至2014年）并覆盖61公里研究区域的航空照片，可知该通道从138±3.4 m缩小至122±2.1 m缩小了12％。漫滩海沟的地层学和沉积学分析以及树年定年证实了空气照片分析，并表明漫漫平原形成的初始阶段始于1930年代中期，大致与总年流量和年峰值流量减少的同时。Tamarisk，一种非本地灌木，也在1930年代开始建立。从1940年代到1980年代中期的缩小幅度很小，因为洪泛区的形成大致与河岸侵蚀相匹配。空气照片分析表明，最明显的变窄现象是在1980年代后期开始发生的，对海沟的分析表明，洪泛平原的形成始于1980年代中期，是多年低峰流量的多年期。空气照片分析表明，从1993年到2009年，平均河道宽度减少了7％左右。根据海沟中的证据，狭窄的新阶段可能已在2003年开始。在1998年和2015年对Fort Bottom附近8.5公里的河段进行的实地调查的比较表明，收窄现象仍在继续，并表明新的洪泛区形成只占绿河年细沙总通量的很小一部分。底堡附近新洪泛区的垂直增生平均为2。在1998年至2015年间4 m，但仅占该时期估算的细沙通量的约1.5％。1962年以后，火焰谷峡大坝进行的洪水控制极大地影响了水流状况，降低了年度融雪洪水的数量，增加了基本流量。尽管变窄是由流态的变化引起的，但本地和非原生河岸植被特别是通过在每年的小规模年度洪水期间在河道条和初期洪泛区的建立促进了洪泛区的形成和河道变窄。