BSF-NSF: Collaborative Research: Deciphering the role of extreme rainstorms and hydroclimatic regime on arid escarpment retreat and sub-cliff slope evolution

沙漠风景通常包括一排排布满巨石和碎片的悬崖，对徒步旅行者和公路工程师来说都是障碍。虽然对于普通的驾车者来说可能并不明显，但这样的沙漠悬崖或悬崖峭壁包含着环境变化的线索。例如，在山体滑坡和风暴期间，悬崖上散落的碎片讲述了过去几千年前降雨量和温度变化的故事。直到最近，人们还只能大致了解这个故事的梗概。今天，新的数据和技术使我们有可能更清楚地解读这个故事。利用机载激光测量获得的详细地形图、降雨记录、沉积特征测年的新方法和计算机模拟，这个美国-以色列两国项目开始了解降雨如何长期塑造沙漠地貌，并提供环境变化如何在短期内转化为对人类和邻近基础设施的危害的洞察力。美国国家科学院最近的一份报告强调，对地形变化的原因和后果的理解是最优先的研究项目。为此，干旱地区的悬崖为研究降水和地貌之间的联系提供了天然实验室，这一方面是因为沙漠将植被的混杂影响降到最低，另一方面是因为沙漠独特的地貌被认为反映了过去降雨的变化。该项目测试了与沙漠悬崖退缩相关的地形具有降雨强度-频率关系的特征的假设。该项目利用了美国和以色列的三个地点，跨越了从极度干旱到干旱的水文气候梯度，具有系统变化的暴雨特性。对科罗拉多高原（美国）和内盖夫沙漠（以色列）的高时间分辨率降雨数据（雷达和量具）、激光雷达地形、地质年代学和野外实验的分析将为一套使用景观演化模型的数值实验提供信息。研究了非均质时空暴雨特征对陡坡退缩的影响，提出了将暴雨变率提升到景观演化时间尺度的新方法。该项目的数值模型和数据工具将作为Landlab工具包的新组件开发，这是一个开源模拟软件库，将其效用扩展到更广泛的科学界。该项目的分析和结果还将为犹他州立大学美国原住民STEM指导项目的两个新学习模块提供材料，该项目为新生水平的美国原住民学生提供门户研究经验。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Desert scenery often includes lines of cliffs draped with boulders and debris, presenting obstacles to hikers and highway engineers alike. Although it may not be obvious to the casual motorist, such desert cliffs, or escarpments, contain clues about the changing environment. For example, aprons of debris shed from cliffs during landslides and storms tell a story of past changes in rainfall and temperature, extending back thousands of years in the past. Until recently, it had only been possible to read that story in its broadest outlines. Today, new data and technologies are making it possible to decipher the story much more clearly. Using detailed terrain maps obtained from airborne laser surveys, together with rainfall records, new methods for dating sedimentary features, and computer simulations, this binational US-Israel project sets out to understand how rainfall shapes desert landforms over the long term, and to provide insight into how environmental changes might translate into hazards to people and adjacent infrastructure in the short term.A recent National Academy report highlighted an understanding of causes and consequences of topographic change as a top-priority research item. To this end, arid-region escarpments provide natural laboratories in which to study connections between precipitation and landforms, both because deserts minimize the confounding influence of vegetation and because their distinctive landforms are thought to reflect past changes in rainfall. This project tests the hypothesis that landforms associated with desert cliff retreat bear signatures of rainfall magnitude-frequency relationships. The project leverages three sites in the USA and Israel that span a gradient in hydroclimatic regime from hyperarid to arid, with systematically varying rainstorm properties. Analysis of high temporal resolution rainfall data (radar and gauges), lidar topography, geochronology, and field experiments in the Colorado Plateau (US) and the Negev Desert (Israel) will inform a suite of numerical experiments using a landscape evolution model. The impacts of heterogenous space-time rainstorm characteristics on escarpment retreat will be assessed, and new methods to upscale rainstorm variability to landscape evolution timescales will be developed. Numerical models and data tools for this project will be developed as new components in Landlab Toolkit, an open-source simulation software library, expanding their utility to the broader scientific community. Analyses and results from this project will also provide materials for two new learning modules for the Utah State University Native American STEM Mentorship Project, which provides gateway research experiences for freshman-level Native American students.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.