Improved Hammond’s Landform Classification and Method for Global 250m Elevation Data

Abstract:

In 1964, E.H. Hammond proposed a set of criteria for the classification and mapping of physiographic regions of the United States. He used extensive, field-acquired knowledge of slope, local relief, and profile type to produce a map entitled “Classes of land surface form in the forty-eight States, USA”, regarded as a pioneering and rigorous treatment of regional physiography. With the advent of computer processing and the availability of digital elevation models (DEMs), several researchers have since developed digital landform modeling approaches to map the distribution of physiographic regions. Many of these approaches incorporate Hammond-based or Hammond-modified algorithms for the small study areas. However, these approaches have been criticized as incomplete by failing to consider slope, relief, and profile type in combination.

We propose a new algorithm to map Hammond landforms using 250 m DEM data which faithfully incorporates slope, relative relief and profile type parameters, and uses spatial analysis to characterize each of these elements. We applied the algorithm to a global 250 m DEM to create a new global Hammond’s landforms map. We compare the new Hammond landforms with other global landform maps and assess alignment (visual) with a global hillshade terrain dataset. We comment on the potential uses of these data (e.g. mapping ecosystem distributions) and discuss important distinctions between physiographic regions (e.g. tablelands) and discrete landform types (e.g. mountains).