Topographic Indices, Baltimore

Topographic indices calculated in support of Kelleher and McPhillips (in review). We calculated two topographic indices - absolute sink depth (m) and topographic wetness index (-) - using TauDEM (v. 5.3) software and the D-infinity flow routing algorithm.

Watersheds include Gwynns Falls [gwynn] and Jones Falls [jones]. Naming convention and sites are shown in the associated manuscript. Note that processing for Baltimore is limited to the extent of each watershed that overlaps with the Baltimore city limits, though processing occurred for the entire watershed and was masked to this area.

Values were processed based on the LiDAR digital elevation model (DEM) for Baltimore, linked below in references. As presented in the associated manuscript, all topographic index values were extracted for all surfaces (e.g., bare soil, pavement, sidewalks, and vegetated areas) that excluded open water and building footprints (where topographic processing and DEM coverages are less reliable). Land cover datasets are linked below.

Naming convention for all files first specifies watershed name (Baltimore; gwynn, jones) followed by topographic index type (twi = topographic wetness index, sink = sink depth).

Descriptions for how each topographic index are calculated are specified in the associated manuscript. Generally, sink depths were calculated by differencing the filled and unfilled DEMs, and TWI was calculated from topographic slope and accumulated area, both processed within TauDEM (note: when negative slopes were calculated, these were replaced with very small values, e.g., 0.001).

为支持 Kelleher 与 McPhillips 的研究成果（尚在审稿中），本研究计算了两种地形指数——绝对汇水深度（米）和地形湿度指数（无单位）——利用 TauDEM（版本 5.3）软件及 D-Infinity 流向路由算法。研究流域包括 Gwynns Falls 流域 [gwynn] 和 Jones Falls 流域 [jones]。命名规范及采样点详见相关手稿。值得注意的是，对于巴尔的摩地区的数据处理仅限于与巴尔的摩市界重叠的流域范围，尽管对整个流域进行了处理，但该区域被屏蔽。数据值基于巴尔的摩的 LiDAR 数字高程模型（DEM）进行处理，相关链接见参考文献。正如相关手稿所述，所有地形指数值均从所有地表（例如，裸土、铺装、人行道和植被区域）中提取，排除开放水域和建筑基底（在这些区域地形处理和DEM覆盖不可靠），土地覆盖数据集链接见下文。所有文件命名规范首先指定流域名称（巴尔的摩；gwynn, jones），随后为地形指数类型（twi = 地形湿度指数，sink = 汇水深度）。每种地形指数的计算方法详见相关手稿。通常，汇水深度通过填充与未填充 DEM 的差分计算得出，地形湿度指数则由地形坡度和累积面积计算而来，这两者均在 TauDEM 中进行处理（注意：当计算出的坡度为负值时，这些值被替换为非常小的数值，例如 0.001）。