Alongshore Classification and Morphometric Analysis of Coastal Belts: The State of Oregon, USA

Abstract

Finkl, C.W. and Makowski, C., 2021. Alongshore classification and morphometric analysis of coastal belts: The state of Oregon, USA. Journal of Coastal Research, 37(2), 238–271. Coconut Creek (Florida), ISSN 0749-0208.Classification of the state of Oregon coastal belt (western United States) was based on the interpretation of satellite imagery using the Biophysical Cross-shore Classification System (BCCS). This seven-county, 480-km stretch was subdivided based on coastal archetypes that formed distinct bio-geomorphological and ecological sequences on both alongshore and cross-shore axes. Shore-parallel and shore-perpendicular units were concomitantly determined by cognitive inspection of satellite images, in which cross-shore archetypical sequences were observed in the first instance to have alongshore spread that could be secondarily codified in terms of alongshore catenas. Because shore-normal transects encompass marine, coastal, and terrestrial environments that have a shore-parallel width, it was possible to extrapolate cross-shore classificatory units into alongshore stretches called domains. Characterization of alongshore domains was based on conjoining archetypes into catenary sequences that typify coastal belts both alongshore and cross-shore from adjacent offshore areas to several kilometers inland. Compilation of coastal belt catenas showed that promontories and headlands, which are composed of resistant igneous and metamorphic rocks, function as anchor points along the shore and are interspersed by sedimentary (littoral) coastal belts that contain mainland and barrier beaches backed by dune, wetland, flat (estuaries), or upland archetypes. A consizement of several alongshore domain catenary sequences within a particular coastal segment thus formed an overarching super domain. Typical alongshore super domains consisted of the following sequences: Barrier-Beach-Dune (Ba-Be-Du), Barrier-Beach-Dune-Wetland (Ba-Be-Du-W), Beach-Dune-Upland (Be-Du-U), Beach-Dune-Wetland (Be-Du-W), Beach-Cliff-Upland (Be-Cl-U), Beach-Wetland-Flat (Be-W-F), and Rock-Cliff-Upland (R-Cl-U). Morphometric analysis of each county allowed the determination of specific characteristics for each super domain (e.g., alongshore length, percentage of the county coastal belt, and percentage of the Oregon coastal belt). Furthermore, archetype morphometrics were calculated to show which cross-shore archetypical features were most prevalent along the state's coastal belt. This examination of the Oregon coast showed that the alongshore classification of coastal belts on a regional scale, which is based on cross-shore biophysical interpretations, offers the opportunity to characterize offshore, inshore, and onshore eco-geomorphological features through the use of super domains and morphometric analysis. This approach to coastal classification thus serves as a blueprint for the comprehensive characterization of coastal belts worldwide.