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Design Sequence

This study explores the economic justification of port development, the selection of port locations based on coastal geomorphology, and the processes shaping coastal landforms. It discusses the use of nautical and topographic maps, aerial photography, and site references for port site selection. The impact of sediment budget, longshore transport, erosion, and deposition on coastal features is also examined.

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Design Sequence

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  1. Design Sequence • Economics:is the port economically justified? • Site Selection: Where should the Port be developed

  2. Coastal Geomorphology • Study of Coastal Landforms, Their Origin and Evolution and the Processes That Shape Them

  3. References for Site Selection • Nautical charts: Best for coastal navigation and underwater features • Topographic (quad) Maps: Best for uplands • Aerial photography (including “google Earth” satellite imagery: Good for land features and upland development

  4. Coastal Features

  5. Sediment Budget LOSSES GAINS Longshore Transport Longshore Transport Offshore Bars Sediment Budget Rivers Offshore Deep Water Cliff and Berm Erosion Offshore Bars Onshore Wind Transport Beach Nourishment Beach Mining

  6. Sediment budget 2 Sediment Budget Longshore Transport Cliff Erosion Offshore Sand Bars Longshore Transport

  7. Spit (sediment sink) Erosion Deposition

  8. Cliff Erosion Primary Causes: • Wind & Rain • Freeze Thaw • Waves (high water)

  9. Be careful using old charts 1984 Is the spit in a stable equilibrium? 1990 Or is it eroding?

  10. Alluvial Fans • Created by river sediments deposited into deepwater. • Characterized by relatively flat inter tidal zone and steep rounded outer face. Outer face is usually close to angle of repose (about 2H:1V). • Typically comprised of uniform sand and gravel suitable for construction including dredging and pile driving. • Caution: • River sediments need to be factored into design. • Alluvial fans can have high risk of failure during seismic events.

  11. Alluvial Fans

  12. Before 1964 Earthquake Currently New Cruise Ship Dock Alluvial Fans

  13. Glacial –Terminal & Lateral MorainesBlackstone Bay

  14. Be sure to read the Charts

  15. Cuspate Bar: From 84 SPM Appendix A

  16. Point Hope North Shore Eroding at 10’ per year South Shore accreting at 10’ per year

  17. Accretion Erosion Effect of Coastal Structures

  18. 1000’

  19. Erosion Accretion Original Shoreline Delong Mountain Terminal (Red Dog)

  20. Offshore bars Strong Longshore Currents Offshore Bars

  21. Note: “Feet” not “Fathoms” Most Charts soundings are Fathoms but not always

  22. Port of Anchorage

  23. Headlands Headlands will often have shallow bedrock. Look for irregular contours. Generally higher and steeper shorelines with more difficult onshore access.

  24. Pocket Beaches Pocket Beaches: Situated between headlands. Generally deep deposit of sand & gravel. Easy dredging and pile driving but very active sedimentation.

  25. Areas of Environmental Sensitivity • Kelp • Eel Grass • Other Submerged Aquatic Vegetation (SAV)

  26. Homework 1 CE A675 • 1.Using the Chart for Akhiok Island (black & white copies): • Identify all the sediment sources (red) • Identify all the sediment sinks (blue) • Areas of difficult construction (rocky) • Areas of easy construction (sand & gravel) • Areas that would be environmentally sensitive (green) • 2. We are going to place a fuel storage tank on the island and need to service it with a 400’ long self propelled barge with a 15 foot loaded draft. Show a good location for constructing a dock of a similar length and sketch it in. Allow 3 feet under keel at mllw. Assume prevailing wind & waves are from the South (Bottom of Page). Provide a one page (maximum) write up explaining your Selection.

  27. Homework 1 chart

  28. Homework 1 CE A675 • Using the attached charts of Homer Spit discuss it formation and how it evolved. Is it really a spit or perhaps a terminal moraine or some other type of feature?

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