DOGAMI Open-File Report Series

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Open-File Report O-13-20, Evaluation of erosion hazard zones along the Alsea Bay shoreline between the Alsea Bay Bridge and the Port of Alsea, Lincoln County, Oregon, by Laura L. Stimely and Jonathan C. Allan.

Order publication CD-ROM, $30, from Nature of the Northwest.

CD-ROM includes:

- 41-p. PDF-format text report in print and onscreen versions

- GIS folder:

Engineering structures-—directory contains three GIS shapefiles:
1. 1939 seawall
2. early 1950s riprap
3. early 1980s riprap

Hazard zones-—directory contains 36 GIS shapefiles:
Time period: 2030, 2050, 2100
Sea level rise: low (L), medium (M), high (H)
Storm-induced erosion: 1 = 100-year event (1%),
2 = 50-year event (2%), 10 = 10-year event (10%)

Photos-—directory contains four georeferenced photos and eight non-georeferenced photos

Profile data-—directory contains shapefiles identifying the locations of the beach-dune juncture for each profile (item 1) and the nine beach profiles (item 2 below):
1. alsea_ej
2. alsea_profile_lines

Historical shorelines-—directory contains 13 GIS shapefiles:
1. 1939_vegLine
2. 1962_vegLine
3. 1972_vegLine
4. 1980_vegLine
5. 1995_vegLine
6. 1997_vegLine
7. 1998_vegLine
8. 2000_vegLine
9. 2005_vegLine
10. 2008_vegLine
11. 2009_vegLine
12. Apr2011survey_vegLine
13. Oct2010survey_vegLine

Also see Microsoft Word formatted files in the GIS folder for detailed metadata for shapefiles.

from the report introduction:
The Oregon Department of Geology and Mineral Industries (DOGAMI) has been commissioned to carry out an assessment of existing and potential coastal erosion hazards along the southeast shore of Alsea Bay, located between the Alsea Bay Bridge and the north point of the Port of Alsea property (Figure 1). The need for this study stems from the effects of recent winter storms and the landward shift in an ebb-tide channel adjacent to the shore, which has resulted in the erosion of the beach and dune, raising concerns by local landowners about the potential risk of ongoing future erosion to their properties. This project will enable the City of Waldport, Port of Alsea, Oregon Department of Land Conservation Development (DLCD), and property owners to have greater knowledge of erosion hazards, particularly in response to potential future climate changes associated with sea level rise. This investigation is not intended for use as a site-specific analysis tool; rather, the study can provide a more holistic understanding of the processes driving coastal change adjacent to the community of Waldport. It will enable the City of Waldport and Port of Alsea to consider erosion hazard data when planning for future protection of natural resources and development.

The overall goal of the project is to develop erosion hazard maps and a report documenting the historical, contemporary, and potential future coastal changes along the shore between the Alsea Bay Bridge and the north point of the Port of Alsea property. The maps and accompanying report can then be used by the City of Waldport and the Port of Alsea to address the objectives of statewide goals and to establish local provisions for the protection of both natural resources and nearby development.

Changes in the position of shorelines (in the form of erosion or accretion) and the shape of the beach are a response to many complex factors that include available sand supply, wave energy, variations in water level, nearshore bathymetry, shoreline orientation, and the geology of the region. To understand these influences throughout our study area, we performed the following tasks:

This report documents the methods and results associated with the objectives outlined in the above tasks.

Funding was provided by Oregon Department of Land Conservation and Development contract PS 09026.

Figure 1 from DOGAMI OFR O-13-20, ALsea Bay study area

Figure 1. Waldport, Oregon, study area. Red outline identifies the section of shoreline studied as part of this report.