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DOCUMENTING CHANGE AT UPPER HAMBURG BEND: NEBRASKA'S FIRST SIDE-CHANNEL RESTORATION

机译:汉堡上弯曲处的文档更改:内布拉斯加州的第一个侧面通道恢复

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In 1996 a side channel was excavated on 629 hectares of former agricultural land at Upper Hamburg Bend on the Missouri River in Otoe County, NE. This was the first side channel constructed on the Missouri River in an attempt to restore lost aquatic habitat. The initial design was for an approximately 4,200 m long side channel to be constructed with a 3 m bottom width. Development ofthe site was to be dependent on flows diverted from the main channel of the river with a final projected top width of 61 m. The side channel was completed in the spring, and shortly thereafter the site was subjected to a series of flood events. The side channel has been subjected to periods of both high and low water since opening. We documented physical changes at the site with the aid of aerial photography, acoustic Doppler current profiler (ADCP) surveys, and topographic surveys. By 2010 the side channel was 4,342 m long with a mean top width of89.5 m. Channel development has occurred during periods of high and low water. ADCP surveys established that mean depths and velocities have increased since 2001. An increase in the amount of discharge through the side channel since 2001 has resulted in the loss of some of the shallower and lower velocity habitats. Modifications to the site may be necessary to reverse this loss of shallow, slow water habitat that the side channel was designed to provide. Although new off-channel aquatic habitat has been created, channel development has been impacted by the presence of rock control structures throughout the site. Reducing the number of control structures to the minimum necessary to prohibit the side channel from impacting adjacent properties may allow the continued restoration of lost alluvial processes through the ongoing process of bend development and migration.
机译:1996年,在内河州Otoe县密苏里河上游汉堡弯上629公顷的旧农业土地上开挖了一条边沟。这是在密苏里河上建造的第一个侧河道,旨在恢复失去的水生生境。最初的设计是建造一条约4200 m长的侧通道,底部宽度为3 m。该场地的开发将取决于从河流主河道分流的流量,最终预计的顶部宽度为61 m。边道在春季完工,此后不久,该地点遭受了一系列洪灾事件。自打开以来,旁通道一直处于高水位和低水位的时期。我们借助航空摄影,声学多普勒电流剖面仪(ADCP)调查和地形调查记录了现场的物理变化。到2010年,侧河道长为4,342 m,平均顶部宽度为89.5 m。河道发展发生在高水位和低水位期间。 ADCP的调查确定,自2001年以来,平均深度和速度有所增加。自2001年以来,通过边道排放的水量增加,导致一些浅水和低速生境的丧失。可能需要对该位置进行修改,以扭转侧通道旨在提供的浅水缓慢生境的丧失。尽管已经创建了新的河外水生生境,但整个场地中存在的岩石控制结构影响了河道的发展。将控制结构的数量减少到禁止旁通道影响相邻特性所需的最小数量,可以允许通过正在进行的弯曲发展和迁移过程来继续恢复失去的冲积过程。

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