The Sitka airport’s runway is built on fill connecting islands in Sitka Sound. The runway is subject to high winds due to its exposed location. Rocks wash onto the runway during storms and large flocks of birds live close to the airport, causing a potential hazard.
The Federal Aviation Administration required Sitka Airport to expand its runway safety area. However, expansion at this location could affect tidal circulation, water quality, and wave climate at nearby locations including Sitka Sound.
In 2012, Mott MacDonald was retained to provide coastal analysis needed for an Environmental Impact Statement on the expansion project. We visited the site, assessed its features, and developed a detailed plan of study.
Mott MacDonald collected existing and new field data needed to calibrate and verify its numerical models. We used the 2D model SWAN to perform wave propagation modeling, the 2D model ADCIRC to model tidal circulation, and the SEDTRANS model to analyze sediment transport and bottom scouring.
Based on the data collected and analyzed, we developed design criteria for the project. These included wave and current forces on structures, wave height for the sizing of revetment armor and toe protection, and the potential depth of scouring to be expected in front of structures.
These findings will provide a basis for a project to improve safety at the airport without causing negative and unexpected impacts on the local environment.