Significant Topographic Changes in the United States

Results

The primary result of the data processing explained in the Methods section is a polygon feature dataset that locates and describes the areas in the conterminous United States that have experienced significant topographic change during the 20th century. 

Filter Total Items: 21
Date published: October 31, 2019
Status: Active

Ranking Features Based on Magnitude of Change

Each of the polygons in the topographic change inventory has numerous attributes associated with it. These attributes allow a ranking of features based on the magnitude of change, as measured by polygon descriptors (area and volume) and changes in terrain parameters (elevation, relief, slope, aspect). The ability to do such a ranking points out one of the advantages of producing spatially...

Date published: October 27, 2019
Status: Active

Quadrangle Base Maps

Many resource managers and geospatial data users are familiar with the USGS 7.5-minute quadrangle map series. Also, much of the geospatial data managed by the USGS was originally produced in tiles corresponding to the 7.5-minute maps. The topographic map quadrangles are still commonly used as base maps for outlining data collection strategies and defining project boundaries. Thus, it is useful...

Date published: October 27, 2019
Status: Active

1x1-Degree Tiles

Summary statistics were also accumulated on the basis of the 1x1-degree tiles used for data management and processing. A total of 500 tiles contain topographic change polygons (see figure below), which represents over 53 percent of the conterminous United States tiles.

Date published: October 27, 2019
Status: Active

Regional Geography of Topographic Surface Changes

The spatial distribution of the topographic change polygons across the conterminous United States reveals some notable regional differences and patterns of change. Overall, there is a decided concentration of change polygons in the eastern United States, which can be partially explained by the greater population density as compared to the west.

Date published: October 26, 2019
Status: Active

Proximity of Topographic Change Areas to Other Features

The near-national extent of the topographic change dataset also allows for spatial comparisons, such as proximity of change polygons to roads and urban areas. Such comparisons have been done for the proximity of mines to roads and major cities for the five focus ecoregions. This figure shows the locations of the centroids of mining polygons within the five ecoregions and the locations of...

Date published: October 26, 2019
Status: Active

Regional Differences in the Effects of Surface Mining

Because the topographic change inventory has near-national coverage, comparisons can be made among broad regions. This figure shows a set of five Level III ecoregions that were used as a basis for regional comparisons of topographic change.

Date published: October 26, 2019
Status: Active

Visual Impacts

When contrasting the general nature of anthropogenic processes versus other geomorphic agents, the visual impact of human activity generally is greater than that of natural processes.

Date published: October 26, 2019
Status: Active

Hydrologic Effects

Because the shape of the land exerts strong control over the collection and flow of surface water, changes to the topography can have a significant effect on local drainage conditions. The figure below demonstrates how the local surface drainage features have been altered as a result of surface mining operations.

Date published: October 26, 2019
Status: Active

Comparison with Land Cover Status and Trends Data

The topographic changes detected in this study usually have a corresponding land cover change. To examine this relationship more closely, features in the topographic change inventory were compared with data from an ongoing study of the status and trends of land cover in the United States. The status and trends project uses a sampling-based approach in which land cover maps and change products...

Date published: October 26, 2019
Status: Active

Error Sources, Uncertainty, Limitations, and Uses

In a study such as this one, with diverse input datasets that cover a broad area, data characteristics and quality can have spatially varying effects on derived information. In the context of data processing methods, unique characteristics of both the NED and SRTM data had to be accounted for in the processing approach to reduce errors of commission. While it is desirable to have a final...

Date published: October 19, 2019
Status: Active

Managed Areas

A delineation of managed areas (Federal, State, tribal, and military lands) from the USGS National Atlas was overlaid on the topographic change inventory. Note that this representation of managed lands is from a small-scale map source and does not include all Federal lands, while others are generalized. About 11 percent of the change polygons fall within the general boundaries of the managed...

Date published: October 19, 2019
Status: Active

Watersheds

Because they are a natural partitioning of the land surface, watersheds have been used extensively to study and report on environmental conditions. As such, they provide another useful way to view and present the extent of topographic changes. The connectivity of watersheds may be an important condition when assessing the impacts of land surface transformations. For instance, an important...