Evaluation of conditions leading to inundation of the airstrip serving the remote village of Kaktovik, North Slope, Alaska

Transportation of goods and people to the Native coastal village of Kaktovik, Alaska (population <300, census 2000) is restricted to sea or air as there are no maintained roads leading to the village. Transport via sea is economically prohibitive and limited by rough seas and ice cover for most of the year and as such the people of Kaktovik rely heavily on scheduled commercial and charter flights. Limited records and anecdotal evidence indicate that landings have been cancelled more frequently in recent years during the open water season (July-September/October) due to overwash and inundation of the runway which is located on a low lying spit partially protected by a barrier island. In this study we investigate the primary meteorological conditions responsible for overwash of the runway by applying a numerical model to simulate waves and storm surge levels due to winds and barometric pressure gradients. High resolution elevation data obtained with aerial lidar (USGS 2009) and acoustic bathymetry measurements collected in August 2010 are used for model boundaries. Atmospheric forcing conditions are defined with spatial- and time-varying hind-cast winds and pressure gradients (NCEP reanalysis 3). Measured water levels obtained in 2008 (NOAA) and 2010 (USGS) are used to calibrate and validate the model as are simulations of reported overwash events. The validated model is used to explore the types and effect of variations in the forcing parameters on runway inundation. Results indicate that inundation and overwash of the spit is primarily due to the combined effect of storm surge and wave runup, but that storm surge has a proportionally greater effect as compared to wave runup. Simulation results also indicate that the storm surge is mostly driven by wind-induced setup and less by reductions in sea level pressure. Sustained west/northwest winds in excess of 12 m/s are shown to generate storm surge levels capable of inundating the runway at its present elevation above sea level. Trends in the frequency of occurrence of overwash caused by winds are assessed by an analysis of hind-cast NCEP r3 wind data for the region.