Collaborative Research: RAPID Assessment of 2013 Flood Sedimentation, Button Rock Reservoir, North St. Vrain Watershed, CO

这个RAPID合作项目将评估2013年9月极端事件发生后，位于科罗拉多州中北部圣Vrain流域的Button Rock水库的洪水沉积。此外，它将填补关于火灾和洪水事件沉积的知识空白，并利用1950年水库建设以来的沉积物积累记录，将知识扩展到年和年代际尺度。沉积记录将提供盆地平均侵蚀速率和沉积的趋势，以及自然或人工湖泊中碳储存的趋势，以及北圣Vrain溪在过去60年里从单一、大型事件到流动情景下的碳输出速率。Button Rock水库提供了一个独特的环境，可以评估Front Range地区罕见的高震级洪水的影响，因为(1)水库运营商自水库建设以来没有进行过故意冲刷事件，(2)水库地层学记录了不间断的三角洲沉积，(3)这是唯一一个不受阻碍的河道上水库。在没有显著的历史木材采伐、水流调节或土地利用影响的情况下，从大陆分水岭到盆地山前的自然沉积物通量。该团队将在2013年12月至2014年3月期间在三角洲沉积物中收集四个岩心。将完成对暴露的三角洲和水库水下部分的探地雷达调查。再加上建坝前的地形图信息，这些岩心和探地雷达调查的信息将限制沉积物沉积的体积和空间分布。从三角洲岩心采集的样本将用于放射性碳分析，以限制沉积物积聚，并通过盆地平均侵蚀速率提供对景观剥蚀的洞察。集水区内的碳通量将由三角洲沉积物中的有机碳含量确定。将流量和降水记录与岩心信息进行比较，分析水库泥沙通量在事件驱动和季节驱动下的变化趋势。该项目将收集一个独特的不间断和不受干扰的记录，记录过去六十年来洪水和火灾对科罗拉多州前山脉侵蚀的影响。它将有助于了解景观如何对这些重大事件做出反应，以及这些事件在景观中碳在储存点之间移动中的作用。这项工作的近期成果将是对2013年9月天气事件造成的物质移动量的精确估计——这一事件迫使朗蒙特市从巴顿溪水库移除相关的沉积物脉冲，以恢复水库容量。该项目为研究生和本科生提供了培训经验，在两所大学的同事之间建立了新的合作关系，并将与管理Front Range沿岸水和沉积物流动的实体共享信息。

This collaborative RAPID project will assess flood sedimentation in Button Rock Reservoir, North St. Vrain watershed in north-central Colorado following the September 2013 extreme event. In addition, it will fill knowledge gaps about event-based sedimentation from fires and floods, and expand knowledge to annual and decadal scales using a record of sediment accumulation since construction of the reservoir in 1950. The sedimentary record will inform on trends in basin-averaged erosion rates and sedimentation, as well as on trends in carbon storage in natural or artificial lakes, and on rates of carbon export from North St. Vrain Creek under flow scenarios from single, large events to flows over the past six decades. Button Rock Reservoir provides a unique setting to assess the effects of a very high magnitude, infrequent flood in the Front Range because (1) no intentional flushing events have been conducted by the reservoir operators since construction of the reservoir, (2) the reservoir stratigraphy chronicles uninterrupted delta deposition, and (3) this is the only on-channel reservoir with unimpeded, natural sediment flux from the Continental Divide to the mountain front in a basin with no significant historic timber harvests, flow regulation, or land use impacts. The team will collect four cores within the delta deposit during the December 2013 to March 2014 timeframe. A ground-penetrating radar survey will be completed of the exposed delta and subaqueous portions of the reservoir. Together with information from pre-dam topographic maps, information from these cores and the GPR survey will constrain the volume and spatial distribution of sediment deposition. Samples from the delta cores will be collected for radiocarbon analysis to constrain sediment accumulation and provide insight into landscape denudation through basin-averaged erosion rates. The carbon flux within the catchment will be determined from organic carbon content in delta sediments. Discharge and precipitation records will be compared with the core information to analyze trends in sediment flux into the reservoir in response to event-based and seasonal drivers.This project will collect a unique uniterrupted and undisturbed record of the impact of floods and fires on erosion in Colorado's Front Range over the past six decades. It will inform understanding of how the landscape responds to such major events and the role of these events in moving Carbon among storage points in the landscape. A near-term outcome of the work will be a refined estimate of the amount of material moved by the September 2013 weather event--an event that has necessitated the City of Longmont to remove the associated pulse of sediment from the Button Creek Reservoir in order to regain reservoir capacity. The project presents training experiences for graduate and undergraduate students, forges a new collaboration between colleagues at two universities, and will share information with entities that manage water and sediment flows along the Front Range.