LITTORAL DRIFT AND SPIT DEGRADATION ON HOMER SPIT, ALASKA. INTERIM REPORT

Homer Spit is a natural littoral formation (0.3 miles wide at its distal end and 4 miles long) extending into Kachemak Bay, an arm of Cook Inlet in South Central Alaska. The end of the spit is heavily developed with fishing and recreational facilities and has been a traditional port for over two centuries. A State highway connects these facilities with the mainland but is subject to heavy wave attack, which periodically results in the failure of the highway and its appurtenant erosion control structures. Over the years, several different structures have been tried including sheetpile walls, heavy riprap, and groins of various materials. A storm in the spring of 1982 resulted in the failure of a section of sheetpile wall flanked by riprap. Peratrovich, Nottingham & Drage, Inc., designed an emergency concrete block revetment comprised of 8-ft by 8-ft by 1.5-ft pre-cast unreinforced concrete blocks, resting on a prepared slope overlain with heavy filter fabric to protect the repaired sheetpile wall and roadway above it. Design wave for this project was 13 feet. To monitor this project's performance, wave environment, and the littoral drift patterns leading to the repeated failures, the State of Alaska commissioned Peratrovich, Nottingham, & Grage, Inc., to do a term research study. The object of this study is to confirm a theory that the artificial structures create high energy "transfer" zones at their margins which deprive the beach in these areas of drift sand that normally protects the spit and roadway. Therefore, each new structure would merely starve the adjacent down-drift section of unprotected beach. This program utilized existing aerial photography to monitor historical changes in the spit and to determine the spit's response to new structures. In addition, new photography was used to quantify changes in the beach profile, particularly with regard to that section of the beach on which the concrete block revetment was built. This interim report presents results of the study to-date, including recommendations for future study.

• Corporate Authors:

  Alaska Department of Transportation and Public Facilities

  2301 Peger Road
  Fairbanks, AK  United States  99701
• Authors:
  • Nottingham, D
  • Drage, B
  • Gilman, J
• Publication Date: 1983

Media Info

• Pagination: 27 p.

Subject/Index Terms

• TRT Terms: Aerial photography; Concrete blocks; Drift; Failure; Filter fabric; Littoral; Monitoring; Revetments; Riprap; Sand; Sheet piling; State highways; Waves
• Uncontrolled Terms: Change; Profiles
• Geographic Terms: Homer Spit (Alaska)
• Old TRIS Terms: Littoral drift
• Subject Areas: Design; Highways; Marine Transportation; Planning and Forecasting; I21: Planning of Transport Infrastructure;

Filing Info

• Accession Number: 00488160
• Record Type: Publication
• Source Agency: Alaska Department of Transportation and Public Facilities
• Report/Paper Numbers: AK-RD-83-24
• Files: TRIS, STATEDOT
• Created Date: Sep 30 1989 12:00AM