Regional landslide hazard using Landlab - NOCA Data

This NOCA landslide data repository host the driver code and data files needed to run Landlab's LandslideProbability component, which models annual shallow landslide probability in a steep mountainous region in northern Washington, U.S.A. The model application covers North Cascade National Park Complex (NOCA), using 30-m grid resolution over 2,700 km2. The model use the classic infinite slope, limited equilibrium model driven by contemporary climatology from the Variable Infiltration Capacity (VIC) macroscale hydrology model. Readily available topographic, geophysical, and land cover data are provided to calculate the factor-of-safety stability index in a Monte Carlo simulation, which explicitly accounts for parameter uncertainty.

Data used for this analysis are spatial data on landscape characteristics for NOCA. They include soil, geology, vegetation, topography, and landform data that can be used for quantitative landslides hazard assessment. Elevation was acquired from National Elevation Dataset (NED) at 30 m grid scale; other datasets are matched to scale and location. Slope was derived from the elevation file as \"tan theta\". Specific contributing area represents the 'upstream' area draining to each cell divided by the cell's width (so minimum value is 30 m). Landform data was developed by Jon Riedel of National Park Service. Landslides were extracted from these data identified as \"mass wasting\" events. Land use and land cover (LULC) data were acquired from USGS National land Cover Data (NLCD) based on 2011 Landsat satellite data and grouped into eight general categories. Cohesion represent total cohesion, which is equivalent to root cohesion in this application; soils are assumed to be primarily cohesionless, lacking “true cohesion” because of their low clay content in this mountain terrain. Root cohesion is based on the LULC referenced to a look-up table within this resource: (https://www.hydroshare.org/resource/a771ba9bbae24ed8b4673c945fc321a3/). Soil depth comes from Soil Survey Geographic Database (SSURGO) maintained by NRCS processed as soil survey depth-to-restricted layer (weighted-average aggregation) within each soil map unit. An alternative modeled soil depth (SD) described in the accompany paper is also provided, but revisions in the driver notebook would be required to reference this file to see adjusted results. Transmissivity was derived from the soil survey saturated hydraulic conductivity (depth averaged) multiplied by depth-to-restricted layer for each soil map unit; another T file based on the model soil depth is also provided. However, the model can be run using hydraulic conductivity using data file provided to calculate T. All soils within this watershed are sandy loam or loamy sand; therefore, soil surface texture was used as an indicator of internal angle of friction (phi). A header file is provided to understand the spatial details of the ASCII files and to facilitate capability with GIS. Spatial reference for raster mapping is NAD_1983, Albers conical equal area projection.

The model run archived in this resource runs with Landlab version 1.1.0 . The component code (landslide_probability9Jun17.py) is provided as an archive to run a notebook that replicates results in Strauch et al., (in review) . As Landlab is developed with newer versions, the notebook and/or provided component code may need updating to run properly. To run the notebook to replicate results, use the resource \"Regional Landslide Hazard Using Landlab - NOCA Observatory\", HydroShare resource: https://www.hydroshare.org/resource/07a4ed3b9a984a2fa98901dcb6751954/

本北美喀斯喀特国家公园群（North Cascade National Park Complex，简称NOCA）滑坡数据集仓库存储了运行Landlab滑坡概率组件所需的驱动代码与数据文件，该组件用于模拟美国华盛顿州北部陡峭山区的年度浅层滑坡发生概率。本模型的应用范围覆盖NOCA区域，采用30米网格分辨率，覆盖面积达2700平方千米。模型采用经典的无限边坡极限平衡模型，由可变入渗容量（Variable Infiltration Capacity, VIC）大尺度水文模型输出的当代气候数据驱动。本仓库提供了易于获取的地形、地球物理与土地覆被数据，用于通过蒙特卡洛模拟计算安全系数稳定性指数，该模拟显式考虑了参数不确定性。

本分析所用数据为NOCA区域的景观特征空间数据集，涵盖土壤、地质、植被、地形与地貌数据，可用于定量滑坡危险性评估。高程数据源自30米网格尺度的国家高程数据集（National Elevation Dataset, NED）；其余数据集均匹配该尺度与空间位置。坡度由高程文件以“tanθ”形式推导得出。比汇流面积指的是“上游”汇至每个栅格的汇水面积除以栅格宽度，因此其最小值为30米。地貌数据由美国国家公园管理局的Jon Riedel开发。滑坡数据提取自被标记为“块体运动（mass wasting）”的事件。土地利用与土地覆被（Land Use and Land Cover, LULC）数据源自美国地质调查局基于2011年Landsat卫星数据的国家土地覆被数据（National Land Cover Data, NLCD），并被划分为8个大类。

黏聚力代表总黏聚力，在本研究场景中等同于根系黏聚力；由于该山区地形的土壤黏土含量较低，假设土壤基本为无黏聚力，缺乏“真实黏聚力”。根系黏聚力基于参照本资源内查找表的土地利用与土地覆被类型得出，相关查找表链接为：https://www.hydroshare.org/resource/a771ba9bbae24ed8b4673c945fc321a3/。土壤深度数据源自美国自然资源保护局（Natural Resources Conservation Service, NRCS）维护的土壤调查地理数据库（Soil Survey Geographic Database, SSURGO），处理方式为按每个土壤图斑内的受限土层深度进行加权平均聚合。本资源还提供了配套论文中描述的另一套模拟土壤深度（SD）数据，但需修改驱动notebook以引用该文件，从而查看调整后的结果。导水率由土壤调查获得的饱和导水率（深度平均）乘以每个土壤图斑的受限土层深度推导得出；本资源同时提供了基于模拟土壤深度的另一套导水率文件。不过，模型也可利用提供的导水率数据文件运行。本流域内的所有土壤均为砂壤土或壤质砂土，因此以土壤表层质地作为内摩擦角（φ）的指示参数。本资源提供了头文件，用于说明ASCII文件的空间细节，并支持GIS软件兼容。栅格制图的空间参考为NAD_1983阿尔伯斯等积圆锥投影。

本资源中存档的模型运行基于Landlab 1.1.0版本。提供的组件代码（landslide_probability9Jun17.py）已打包，可用于运行复现Strauch等人（待发表）研究结果的notebook。随着Landlab版本更新，该notebook与/或提供的组件代码可能需要更新以正常运行。如需复现研究结果运行该notebook，请使用HydroShare资源“Regional Landslide Hazard Using Landlab - NOCA Observatory”，链接为：https://www.hydroshare.org/resource/07a4ed3b9a984a2fa98901dcb6751954/