Montana Human Disturbance Index

Data Provider Montana Natural Heritage Program (MTNHP)
Date 10/11/2016
Content Type Downloadable Data
Abstract The Montana Human Disturbance Index (HDI) represents six disturbance categories: Development, Transportation, Agriculture, Resource Extraction/Energy Development, Introduced Vegetation, and Forestry Practices. As an index, this dataset has no units. The HDI ranges from 0-4,314. A value of 0 indicates no human disturbance. Larger values indicate increasing levels of disturbance.
Purpose To determine a Human Disturbance Index score for a given pixel. The original purpose of this layer was to characterize the degree of human disturbance for use in selecting potentially restorable wetlands.
Supplemental Information We identified six categories incorporating 24 individual disturbances. We assumed that the impact of each disturbance on aquatic resources decreases, or decays, with increasing distance. Following Lemly et al. (2011), we used a sigmoid (s-shaped) curve to represent the behavior of each modeled disturbance impact, as this type of curve allows for several parameters to be defined. The curve can decay gradually with increasing distance from the source of the disturbance, or it can decay abruptly, meaning the impact of the disturbance drops substantially at a short distance from the disturbance. Values of a and b can be adjusted based on the type of decay curve applied. The curve is asymptotic, and the results of the equation equal the maximum weight of the disturbance at zero distance and the minimum weight where the impact is essentially zero. A weight and overall decay curve type are applied to each disturbance. For each data layer, we calculated the Euclidean distance from each pixel in the raster to the closest source of the disturbance. As a result, each disturbance has an associated Euclidean distance raster. We then applied the appropriate distance decay function to each Euclidean distance raster. Resulting raster layers were then summed to create the final HDI raster. For some disturbance categories, only the maximum value of the disturbance was included in the final HDI raster to reduce the confounding effect of certain disturbances. The final raster was created via a Python script,, that is included in the data download. A table of the model parameters is included in the data download. See process steps section for further detail. Methods were based on Lemly, J., L. Gilligan, and M. Fink. 2011. Statewide strategies to improve effectiveness in protecting and restoring Colorado's wetland resource. Colorado Natural Heritage Program, Colorado State University.
This is a model based on currently available data and was created at a statewide scale. A model is only as good as its input data and the assumptions of the parameters used. The input data are known to have errors, omissions, and inaccuracies. This layer should be used as an initial screening or planning tool at a scale no less than 1:100,000. It is inappropriate to use this layer for small-scale analyses. The parameters and model weights were based on best professional judgment and are intended to reflect predicted impacts on aquatic resources. These assumptions may not be appropriate for other resource types. The Montana HDI is provided as-is.
Data Access
Distributor Linda Vance
PO BOX 201800
Helena, MT 59620-1800
Telephone: 406-444-3380
Distribution liability Users must assume responsibility to determine if these data are suitable for their purposes.
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Metadata date 10/12/2016

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