Hydrography of Port Valdez and Valdez Glacier Lake
Aiding Disaster Planning and Nautical Charting
Woolpert conducted a hydrographic survey of Port Valdez and Valdez Glacier Lake for the NOAA Office of Coast Survey, in collaboration with the City of Valdez, with support from the Brennan Ocean Mapping Fund. The survey area included Port Valdez Fjord, Shoup Bay, the Valdez Narrows, and newly exposed sections of Valdez Glacier Lake Much of the fjord’s landscape reflects glacial scouring and glacial moraine deposits, however significant post-glacial sediment deposits fill the basin floor. These include landslide debris flows, the most recent of which averaged 20m in thickness. (Roland, E., Haeussler, P., Parsons, T., & Hart, P. 2020).
The bathymetric data collected will serve as a modern baseline to support earthquake hazard assessment, modeling, and emergency response planning. Additionally, the survey provides updated bathymetry for NOAA nautical charting products, enhancing maritime safety and commerce, and contributes to the Seabed 2030 global ocean mapping initiative.
Valdez Glacier Lake
Valdez Glacier Lake formed due to deglaciation over the last few decades. For Valdez Glacier Lake, Woolpert utilized an uncrewed surface vessel that was towed alongside a skiff. This modular configuration allowed the deep water multibeam sonar to be deployed in the lake and allowed the crew to navigate shallow and narrow passages between and over icebergs. The Valdez Glacier Lake survey was conducted with the support of a local kayak guide as route finding between the building sized, drifting, icebergs required advanced scouting.
Project Goals
Tsunami preparedness: Understanding the underwater landscape helps scientists see how waves might move during a landslide or earthquake.
Finding hazards: Maps can show steep slopes, deep holes, or unstable areas that may be dangerous.
Navigation and safety: Clear maps make Port Valdez safer for shipping, fishing, and recreation.
Future planning: The data will help the city and scientists plan ahead and be ready for emergencies.
Survey Methodology
Full coverage hydrographic data was acquired from Woolpert’s survey vessel Inverness using multibeam sonar. The sonar was operated at 90 to 300kHz and the data was gridded at 1 to 8 meters depending on depth. Cold, turbid, freshwater flows into Port Valdez and creates thermoclines in the water column. To dampen the range and refraction errors, the bathymetric data was acquired in subset areas, sound velocity profiling frequency was increased, and sound velocity correction application methods were optimized in post processing.
Chart Features
In addition to acquiring bathymetric data, an important aspect of the hydrographic survey was the assessment of known features, such as the middle rock light channel marker and detection of new features, such as the unidentified structures shown below.