HISTORICAL SPATIAL-TEMPORAL EVOLUTION AND MORPHODYNAMICS OF BLOWOUTS IN CAPE COD NATIONAL SEASHORE

Blowout initiation and historical evolution is explored at Cape Cod National Seashore (CCNS), MA, USA; which hosts one of the highest densities of blowouts, of varying morphology, in the world. Although blowouts are very common landforms in desert and coastal landscapes, few studies have explored their morphodynamics and longer-term evolution. Blowout morphology has been linked to changes in climate and human land use activity; however, without comprehensive knowledge of their formation and morphodynamics their use as indicators of landscape or climatic change is limited. This paper explores blowout initiation, evolution, and morphodynamics by examining morphological changes from historical aerial photographic and LiDAR coverage and employs the Spatial-Temporal Analysis of Moving Polygons (STAMP) method, which was developed to study epidemiological phenomenon, as a means to quantitatively explore and describe blowout evolution on a select subset of blowouts within CCNS.

The STAMP method allows for pattern-based detection, quantification, and visualization of changes that occur through time and space. Erosional deflation basins – the concave portion of blowouts - are easily identified and digitized from photographic coverage and STAMP detects changes in basin morphology by analyzing polygon dynamics against neighboring polygon layers and extracting spatio-temporal patterns of movement and geometric change. From this, observed patterns of blowout morphodynamics (e.g. expansion, contraction, stabilization, generation, disappearance, and migration) at CCNS are analyzed and modeled. Examination of this sub-population of features of varying size and (presumably) stages of evolution, allows for classification of common morphodynamic responses and development of an initial model of blowout evolution.