RUI:Erosion in Madagascar: Investigating background and modern rates using 10Be and stream sediment gauging data

RUI：马达加斯加的侵蚀：使用 10Be 和河流沉积物测量数据调查背景和现代速率

• 批准号: 0921962
• 负责人: Rónadh Cox
• 金额: $ 26.17万
• 依托单位: Williams College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-15 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0921962&HistoricalAwards=false
• 关键词: RUI; Erosion; Madagascar; Investigating; background

Conventional wisdom holds that sediment yields in Madagascar are uncommonly high, and that human activities drive the erosion. The country has a "world-record erosion rate" of 20,000-40,000 tons per square km per year according to the World Bank, and the widespread hillslope gullies called lavaka are featured in every guidebook as examples of the catastrophic denudation of the country's landscape. This viewpoint is based, however, on measurements that are few and local, and in many respects represents "received wisdom" rather than rigorously determined interpretation. Systematic analysis is therefore necessary to measure the erosion rate of Madagascar. Cosmogenic 10Be, a short-lived isotope created at the Earth's surface by cosmic-ray bombardment, can determine landscape erosion rates. Undisturbed surface materials accumulate substantial amounts of 10Be, but where erosion is high then surface materials are low in this isotope. Preliminary 10Be analyses of sediment from Madagascar rivers indicate erosion rates of only about 32 tons per square km per year, suggesting that the Madagascar landscape has been quite stable on timescales of thousands to hundreds of thousands of years. On the other hand, direct measurements of sediment yield in rivers can provide erosion rates on shorter timescales (years to centuries). Because humans arrived in Madagascar less than 2000 years ago, collecting and comparing 10Be and sediment gauge data will document erosion rates in the pre-human to modern time span. This project will sample drainage networks from broad swaths of Madagascar, omparing 10Be data with recent sediment data from stream-sediment gauging and reservoir sedimentation records.in order to quantify both background and modern erosion rates. GIS analysis will investigate the relationship between erosion rate and the intensity of lavaka gullying in the watersheds. This project contributes to ongoing efforts to quantify the effects of humans as geomorphic agents world-wide. Madagascar's status as a biodiversity hotspot and a threatened environment lend added significance to the work, as these questions loom large in discussions of conservation and international aid policy. The project will involve both Malagasy and U.S. students and personnel. The scientific results of this project will have direct relevance for environmental planning and erosion mitigation strategies for Madagascar. Understanding rates of erosion, the role of lavakas in sediment generation, and the role of humans in the process will help determine whether Madagascar is naturally characterized by high erosion rates or whether they are of recent and anthropogenic origin. This award is co-funded by NSF's Office of International Science and Engineering.

传统观点认为，马达加斯加的沉积物产量非常高，人类活动是造成侵蚀的原因。根据世界银行的数据，该国每年每平方公里的侵蚀量达到创纪录的2万至4万吨，被称为拉瓦卡的广泛的山坡沟壑作为该国景观遭到灾难性侵蚀的例子出现在每一本旅游指南中。然而，这一观点是建立在少数局部测量的基础上的，而且在许多方面代表了“公认的智慧”，而不是严格确定的解释。因此，有必要进行系统分析，以衡量马达加斯加的侵蚀率。宇宙成因10Be是一种由宇宙射线轰击在地球表面产生的短暂同位素，它可以确定地形侵蚀的速度。未受干扰的表面材料积累了大量的10Be，但在侵蚀程度较高的地方，表面材料的这种同位素含量较低。对马达加斯加河流沉积物的初步10Be分析表明，每年的侵蚀速度仅为每平方公里32吨左右，这表明马达加斯加的地形在数千年至数十万年的时间尺度上一直相当稳定。另一方面，直接测量河流中的泥沙产量可以提供较短时间尺度(几年到几个世纪)的侵蚀率。由于人类到达马达加斯加的时间不到2000年，收集和比较10Be和沉积物测量仪数据将记录从前人类到现代时间跨度的侵蚀速度。该项目将对马达加斯加大片地区的水系进行采样，将10Be数据与水系沉积物测量和水库沉积记录的最新沉积物数据进行比较，以便量化背景和现代侵蚀速率。地理信息系统分析将研究流域内拉瓦卡沟侵蚀强度与侵蚀速率之间的关系。该项目有助于在世界范围内量化人类作为地貌因素的影响的持续努力。马达加斯加作为生物多样性热点和受到威胁的环境的地位增加了这项工作的意义，因为这些问题在保护和国际援助政策的讨论中隐约可见。该项目将涉及马达加斯加和美国的学生和人员。该项目的科学成果将与马达加斯加的环境规划和减缓侵蚀战略直接相关。了解侵蚀速率、熔岩在沉积物形成中的作用以及人类在这一过程中的作用，将有助于确定马达加斯加是以高侵蚀速率为自然特征，还是来自最近的和人为的起源。该奖项由美国国家科学基金会国际科学与工程办公室共同资助。