Nature-based and community-engaged Arctic coastal protection
Investigators
University of Alaska Anchorage
University of Alaska Anchorage
Student
- George Payne, program
Overview
The issue
Arctic Alaska has thousands of miles of shoreline, and accelerating coastal erosion is threatening communities and infrastructure. While our understanding of Arctic coastal processes and erosion has improved in the past several years, additional knowledge is needed. The technologies for countering erosion are not fully effective and need further development. For example, a 400-million-dollar coastal seawall to protect Utqiagvik is currently under design. However, important considerations, such as heat transfer from the ocean to the permafrost beneath the coastal structure, are not yet accounted for. Further, the potential for nature-based coastal technologies is not being fully explored in the Arctic. For instance, communities have observed that sites of marine mammal harvesting are relatively resistant to erosion. Presumably, materials associated with the harvesting, like seal oil, strengthen the coastal soils and sediments. The concept of using soil/sediment additives to improve strength is well-established in geotechnical engineering. However, we are not aware that these techniques have been explored in an Arctic setting. Finally, it is noteworthy that Arctic coastal communities have a special connection to the sea due to their subsistence activities. Hence, the successful development of coastal erosion defense strategies will require significant input and involvement from community members.
Objectives
In this project, we will research fundamental mechanisms of Arctic coastal erosion and explore nature-based erosion mitigating strategies. We will conduct this investigation while fully engaging with Arctic coastal communities, government agencies, and practicing coastal engineers, who will serve on the Steering Committee for our project. Our research will be developed using three mutually supporting approaches, including (1) lab testing of erosion and erosion mitigation, (2) numerical modeling of Arctic coastal erosion and erosion mitigation, and (3) field observations and data collection from an erosional site, and a preliminary design of nature-based coastal protection for that site. First, we will create an Arctic wave flume, utilizing the Cold Room at UAA, which provides a unique platform for conducting Arctic coastal erosion physical model experiments. The Arctic Flume will be designed to simulate soil and hydrodynamic conditions that are present at the Arctic field site, which has already been established in a previous project. In parallel with the development of the Flume and the field work, we will continue to develop a numerical simulation tool for Arctic coastal erosion and erosion mitigation modeling, referred to as “Arctic Xbeach”. Arctic Xbeach is a coupling of Xbeach – an open-source coastal geomorphic change model – with a thermal module that determines the temperature and phase of the soil/sediment. The data collected with the Arctic Flume will be used to calibrate and expand the capacity of the Arctic Xbeach model. The flume experiments and Arctic Xbeach will be used to study the thermal and mechanical processes responsible for Arctic coastal erosion at a field site in Utqiagvik. We will use the Arctic Flume experiments and Arctic Xbeach to explore erosion mitigation approaches for the field site, including solar reflectors, thermal siphons, and the use of soil additives for strengthening the thawing permafrost and slowing erosion.
How will researchers conduct their study?
There are three interrelated methodological elements in this proposal: (1) the Arctic Flume, (2) Arctic Xbeach, and (3) the design of nature-based erosion protection for a demonstration site. The Arctic Flume will be a wave flume designed to simulate erosion of an Arctic coastal bluff and beach, as well as nature-based erosion mitigation technologies such as thermal syphons, solar reflectors, and soil strengthened by additives. A wave maker will be positioned on one end of the flume and a frozen beach equipped with temperature sensors will be positioned on the other side. To simulate Arctic conditions, the Flume will be positioned in the UAA Cold Room, and a water heater will be deployed by the wave maker to keep the water from freezing. The Arctic Xbeach modeling system will be used to help design and simulate the hydrodynamics and erosion in the Arctic Flume, and to simulate those same processes at the Utqiagvik field site. Arctic Xbeach is a coupling of an open-source coastal geomorphic change model (Xbeach) and a thermal model. For example, the convective heat transfer from the nearshore water and the sediment below depends on the wave conditions which is provided by Xbeach. Sediments determined to be frozen by the thermal model are treated as non-erodible material by Xbeach. Arctic Xbeach will determine the heat transfer and warming due to atmospheric heat transfer and due to oceanic heat transfer. Also, Arctic Xbeach will simulate the effect of nature-based technologies such as thermal syphons, solar reflectors, or soil strengthened by soil additives. Arctic Flume and Arctic Xbeach will be used to design the nature-based coastal protection for the Utqiagvik field site. Survey data from the field site allow us to establish the rate of geomorphic change (erosion) during the past ten years (2013-2023) and that data will be used to calibrate Arctic Xbeach. Then, Arctic Xbeach will simulate the effect of the nature-based erosion mitigation technologies.
