Topographic Wetness Index derived from 1" SRTM DEM-H

Topographic Wetness Index (TWI) is calculated as log_e(specific catchment area / slope) and estimates the relative wetness within a catchment.

The TWI product was derived from the partial contributing area product (CA_MFD_PARTIAL), which was computed from the Hydrologically enforced Digital Elevation Model (DEM-H; ANZCW0703014615), and from the percent slope product, which was computed from the Smoothed Digital Elevation Model (DEM-S; ANZCW0703014016). Both DEM-S and DEM-H are based on the 1 arcsecond resolution SRTM data acquired by NASA in February 2000.

Note that the partial contributing area product does not always represent contributing areas larger than about 25 km2 because it was processed on overlapping tiles, not complete catchments. This only impacts TWI values in river channels and does not affect values on the land around the river channels. Since the index is not intended for use in river channels this limitation has no impact on the utility of TWI for spatial modelling.

The TWI data are available in gridded format at 1 arcsecond and 3 arcsecond resolutions.

The 3 arcsecond resolution TWI product was generated from the 1 arcsecond TWI product and masked by the 3” water and ocean mask datasets.

地形湿度指数（Topographic Wetness Index, TWI）的计算公式为自然对数形式的单位汇水面积与坡度的比值，即logₑ(单位汇水面积/坡度)，用于估算集水区内的相对湿润状况。

本TWI数据集源自两部分数据：一是由水文修正数字高程模型（Hydrologically enforced Digital Elevation Model, DEM-H; ANZCW0703014615）计算得到的部分贡献面积数据集（partial contributing area product, CA_MFD_PARTIAL），二是由平滑数字高程模型（Smoothed Digital Elevation Model, DEM-S; ANZCW0703014016）计算得到的坡度百分率数据集。DEM-S与DEM-H均基于美国国家航空航天局（NASA）2000年2月获取的1弧秒分辨率SRTM数据生成。

需注意的是，由于该部分贡献面积数据集基于重叠瓦片而非完整集水区进行处理，其无法准确表征面积大于约25平方千米的贡献区域。该缺陷仅会影响河道内的TWI数值，对河道周边陆地区域的TWI数值无影响。鉴于本指数本就不适用于河道区域，此局限不会对TWI在空间建模中的应用效用产生任何影响。

本TWI数据以栅格格式提供，分辨率涵盖1弧秒与3弧秒两种。

3弧秒分辨率的TWI数据集由1弧秒分辨率的TWI数据集生成，并通过3弧秒水体与海洋掩膜数据集进行了掩膜处理。

搜集汇总

背景与挑战

背景概述

该数据集提供了基于1弧秒SRTM DEM-H数据计算的地形湿度指数(TWI)，包含1弧秒和3弧秒两种分辨率，适用于山坡地形的湿度估计和空间建模，但不适用于河道分析。数据集覆盖澳大利亚特定区域，时间跨度为2000年2月。