Project Snapshot
| Category | Details |
| Client | Stantec |
| Project Name | Dawson City Flood Mapping |
| Location | Dawson City, Yukon Territory |
| Date | 2024 |
| Project Summary | View Summary |
Project Overview
Introduction
Underhill Geomatics supported Stantec on the Dawson City Flood Mapping project from June to October 2024. The work focused on understanding flood risk related to seasonal ice jams on the Yukon and Klondike Rivers. Underhill completed comprehensive land and river surveys-including bathymetry, LiDAR scanning, topographic surveys, and flow measurements- to map historic flood areas and help predict where future flooding may occur. The resulting datasets support long-term flood mitigation planning for Dawson City.
Project Challenges
- Shallow, fast-moving water: Some areas were too shallow for echo sounders, yet unsafe for personnel to wade into due to strong currents.
- Mobile riverbed sediments: Fine sediment and fast flows caused the riverbed to shift noticeably throughout the day, complicating consistent data capture.
- High water levels during freshet: Fast currents and elevated water levels made multibeam collection difficult, as data quality is highly sensitive to vessel speed.
- Remote work environment: Work occurred outside cell coverage, requiring strict safety protocols and daily check-in procedures.
Innovative solutions
- IMU-assisted shallow-water surveying: Underhill used the Trimble R12i’s IMU
capabilities to safely collect data in shallow, fast water by operating an angled survey rod
from a stable position on shore. - Shortened survey windows: In areas with shifting sediment, the team reduced the interval between overlapping passes, ensuring the riverbed was captured as it existed at the moment of survey.
- Modified vessel propulsion: A smaller auxiliary motor was installed on the survey boat, allowing precise speed control to maintain multibeam data quality in strong currents.
- Enhanced safety protocols: Daily check-ins via inReach, coordination with local police, and strict emergency timelines ensured field safety.
Technologies Used
Equipment & Data Capture
- Seafloor SeaRay Multibeam Echosounder
- H30T — high‑resolution thermal, inspection, and video capture
- DJI P1 — high‑accuracy photogrammetry and 3D modeling
- CEE Hydro Systems CEE-LINE single beam echosounder
- DJI Matrice 300 RTK UAV with YellowScan Lidar
- Trimble R12 and R12i GNSS Receivers
- Trimble TSC5/TSC7 Data Collectors
- Trimble S7 Robotic Total Station
- SonTek RiverSurveyor M9 Acoustic Doppler Current Profiler (ADCP)
- Ducksworth 20’ aluminum boat & Stryker 13’ inflatable jet boat
Software
- Xylem HYPACK – multibeam acquisition & cleaning
- YellowScan CloudStation – LiDAR processing
- Applanix PosPac – Inertial Measurement Unit (IMU) processing for LiDAR & multibeam
- Xylem SonTek RiverSurveyor – Acoustic Doppler Current Profiler (ADCP) data collection
Project Highlights
The Underhill field crew also collaborated with local residents in Dawson City to collect historic flood information. Working directly with long-time Dawsonites, the team located and surveyed highwater marks throughout the community – some dating back to the 1970s.
