Monitoring Mountain Rivers From Space: A Pilot Study of Bedrock River Flow Measurement Using Ultra-High Resolution Optical Satellite Imagery

测量山区河流的洪水水位流量是一个巨大的后勤挑战，特别是在大的空间和时间尺度上，这种数据的不可避免的缺乏阻碍了我们对山区景观过程的理解。我们提出了一种新的解决方案，利用新的分辨率卫星图像（2米，FORMOSAT-2）与异常高的重访频率（每日）overa地区的非常广泛的兴趣，地球科学界（台湾）。我们提出的方法需要整理的时间序列（2004-2005年）的orthorectic * 艾德，地理参考图像选定的山区河流渠道，在串联的同期阶段测量的流量在最近的gaugingstation下游。沿着选定的河道河段的淹没模式将在每幅图像中绘制。利用野外绘制的低水位跨河道剖面，估算低水位宽度、深度、平均床面切应力和平均低速。一旦广泛的dischargeshas被处理，我们希望能够构建这些低措施的额定曲线作为直接观察到的功能，在车站阶段的数据。结合台湾多年来测站资料的评估模式，将可评估低宽度、深度与剪应力沿着及横跨所选基岩水道的长期机率分布。这种测量，尽管是间接的，但将引起地貌学界的极大兴趣。然而，这种方法并不能保证，因为偏远的河流测量从来没有尝试在山区集水区;它仍然有待观察，是否预期的额定曲线的精度将足以为河流类似的台湾中央山脉。本试验计画的主要任务将是解决这个问题，并为台湾山区河川流量的更全面、更长期的评估奠定基础。更广泛的成果：虽然对基岩河道过程感兴趣的人特别追求陡峭山区河川的低位测量，但它们也有很大的兴趣：从景观演变的模型和气候与构造之间的相互作用，水文学家专注于人口密集的山区环境中的洪水灾害评估。此外，如果试验计划证明成功，它将为台湾航天局提供一个很好的例子，证明FORMOSAT-2在自然灾害评估中的价值，这是其主要任务之一。因此，将更加注意定期获取热带山区FORMOSAT-2号图像，这是实现高分辨率、多时相图像档案这一难以实现的目标的一个重要步骤-目前，高原地区图像的优先程度相对较低（对于FORMOSAT-2号和其他同等卫星而言），并且仅在紧急时期（例如台风）每天获取。这样的档案将在地球科学、水文学、生态学等学科中得到广泛的赞赏，更不用说在遥感研究和发展本身了。

The measurement of flood-stage discharge in mountain rivers is an enormous logistical challenge, particularly on large space and time scales, and the inevitable paucity of such data has impeded progressin our understanding of mountain landscape processes. We propose a novel solution that exploits newhigh resolution satellite imagery (2m, FORMOSAT-2) with unusually high revisit frequency (daily) overa region of very broad interest to the earth science community (Taiwan). Our proposed method entailsthe collation of a time series (2004-2005) of orthorecti*ed, georeferenced images of selected mountainriver channels, in tandem with contemporaneous stage measurements of discharge at the nearest gaugingstation downstream. Patterns of inundation along selected channel reaches will be mapped in eachimage. With the aid of cross-channel profiles mapped in the field at low stage, we will make estimatesof low width, depth, mean bed shear stress and mean low velocity. Once a broad range of dischargeshas been processed, we expect to be able to construct rating curves for these low measures as a functionof the directly observed, at-station stage data. Combination of the rating models with the multi-decadalarchive of station data in Taiwan will permit an assessment of the long-term probability distributions oflow widths, depths and shear stresses along and across the selected bedrock channels. Measurements ofthis kind, albeit indirect, will be of enormous interest to the geomorphology community. However, themethod is by no means guaranteed, because remote river gauging has never been attempted in mountaincatchments; it remains to be seen whether the precision of the anticipated rating curves will suffice forrivers akin to those of the Taiwan Central Range. The main task of the pilot project will be to addressthis issue and to lay the foundation for a more comprehensive, longer-term assessment of Taiwanesemountain river discharge.Broader outcomes: While low measurements in steep mountain rivers are particularly sought after bythose interested in bedrock channel processes, they are also of great interest beyond: from modelersof landscape evolution and the interaction between climate and tectonics, to hydrologists preoccupiedwith the assessment of flood hazard in populated mountain environments. Moreover, if the pilot projectproves successful it will provide the Taiwanese space agency with an excellent example of the value ofFORMOSAT-2 in natural hazard assessment, one of its principal missions. As a result, more attentionwill be paid to the regular acquisition of FORMOSAT-2 imagery in tropical mountain areas, an essentialstep if the elusive goal of a high-resolution, multitemporal image archive is to be achieved - at present,images of highland areas are a relatively low prioity (for FORMOSAT-2 and other equivalent satellites)and are only acquired daily during emergency periods (e.g. typhoons). Such an archive would be widelyappreciated across the discplines of earth sciences, hydrology, ecology, not to mention in remote-sensingR&D itself.A-1