-- Lake Powell Multibeam Mapping 2005 --
Project Overview
a collaborative research project between:
Ocean Mapping Group, University of New Brunswick, Canada
Dept Earth Sciences, Duke University, NC, USA
National Park Service, Page AZ, USA
Bureau of Reclamation, Denver, CO, USA
- Direct to online mapsheets -
Overview
From May 12th to May 21st, an EM3002 multibeam survey was conducted of the entire length of Lake Powell AZ/UT from the NPS vessel "321". The aim of the survey was to examine the current morphology and sediment distribution on the floor of the lake. This survey follows directly on from sidescan and subbottom surveys of the whole lake conducted in May 2004 collaboratively by Duke and the National Park Service (NPS) and a multibeam survey of the San Juan Arm by the Bureau of Reclamation (BOR) in October and December 2004.
The survey was designed to cover the talweg of the drowned canyon system, from bank to bank. The main Colorado and San Juan arms were the focus, with a significant diversion into the Escalante. Other, smaller side canyons that appeared to be contributing sediment, were also imaged. As noted in the first two sedimentation studies of the lake (in 1977, Condit et al., 1978, and in 1986, Ferrari, 1988), the upper sections of the Colorado and San Juan arms have been accumulating sediment significantly, with up to 50m in the Colorado and 15m in the San Juan in the first 23 years.
Scientific Objectives
The Duke survey had identifed zones in which, rock fall, debris flow and turbidity current processes appeared to be particularily active. These were believed to be rapidly evolving processes and thus a precise baseline bathymetric and backscatter survey was required to monitor the detailed morphological evolution of these sedimentary systems. This survey is designed to be used to quantitative assess spatial variability in volumetric change through follow-up surveys.
Survey Implementation
The survey was conducted using a Simrad EM3002 multibeam system, pole mounted on the MV "321". The system is designed to cover a ~4x water depth swath for depths between 2m and 100m+. Because the lake is fresh, the attenuation coefficient at 300 kHz is only ~30 dB/km (as opposed to typically ~80 dB/km in salt water) and thus the full swath width could be maintained for the full depth range of the lake (max ~130m at the dam).
The EM3002 provides both bathymetric and backscatter imaging. The bathymetric resolution is ~0.2% of depth vertically and ~3% horizontally, and the absolute accuracies are slightly worse depending on integration and control. The backscatter strength values are in principal "calibrated". However, in reality, the system output is really only relative, being corrected for real-time power, pulse length, grazing angle and TVG adjustments.
A number of minor, but systematic artefacts exist in the EM3002 bathmyetric and backscatter data which should be understood to avoid mis-interpretation of the data.
Participants
contact details....
Funding Agencies
The UNB involvement was funded by the National Science and Engineering Research Council of Canada (NSERC). The loan of ,and support for, the EM3002 system was provided by Kongsberg Simrad USA The provision of the MV 321 for the 2 week period was donated by the National Park Service.
Ferrari, R., 1988, 1986 LAKE POWELL SURVEY: U.S. Department of the Interior, Bureau of Reclamation, REC-ERC-88-6, 67pp.
Condit, W., Drake, C.L., Mayer, L. and Spydell, P., 1978, Sedimentation in Lake Powell: Lake Powell Research Project Bulletin, # 64, National Science Foundation.
From May 12th to May 21st, an EM3002 multibeam survey was conducted of the entire length of Lake Powell AZ/UT from the NPS vessel "321". The aim of the survey was to examine the current morphology and sediment distribution on the floor of the lake. This survey follows directly on from sidescan and subbottom surveys of the whole lake conducted in May 2004 collaboratively by Duke and the National Park Service (NPS) and a multibeam survey of the San Juan Arm by the Bureau of Reclamation (BOR) in October and December 2004.
The survey was designed to cover the talweg of the drowned canyon system, from bank to bank. The main Colorado and San Juan arms were the focus, with a significant diversion into the Escalante. Other, smaller side canyons that appeared to be contributing sediment, were also imaged. As noted in the first two sedimentation studies of the lake (in 1977, Condit et al., 1978, and in 1986, Ferrari, 1988), the upper sections of the Colorado and San Juan arms have been accumulating sediment significantly, with up to 50m in the Colorado and 15m in the San Juan in the first 23 years.
Scientific Objectives
The Duke survey had identifed zones in which, rock fall, debris flow and turbidity current processes appeared to be particularily active. These were believed to be rapidly evolving processes and thus a precise baseline bathymetric and backscatter survey was required to monitor the detailed morphological evolution of these sedimentary systems. This survey is designed to be used to quantitative assess spatial variability in volumetric change through follow-up surveys.
Survey Implementation
The survey was conducted using a Simrad EM3002 multibeam system, pole mounted on the MV "321". The system is designed to cover a ~4x water depth swath for depths between 2m and 100m+. Because the lake is fresh, the attenuation coefficient at 300 kHz is only ~30 dB/km (as opposed to typically ~80 dB/km in salt water) and thus the full swath width could be maintained for the full depth range of the lake (max ~130m at the dam).
The EM3002 provides both bathymetric and backscatter imaging. The bathymetric resolution is ~0.2% of depth vertically and ~3% horizontally, and the absolute accuracies are slightly worse depending on integration and control. The backscatter strength values are in principal "calibrated". However, in reality, the system output is really only relative, being corrected for real-time power, pulse length, grazing angle and TVG adjustments.
A number of minor, but systematic artefacts exist in the EM3002 bathmyetric and backscatter data which should be understood to avoid mis-interpretation of the data.
Participants
University of New Brunswick:
- John E. Hughes Clarke
- Jonathan Beaudoin
- Lincoln Pratson
- Mark Anderson
- Jesse Granet
- Lex Newcombe
- Ron Ferrari
- Mark Rice
contact details....
Funding Agencies
The UNB involvement was funded by the National Science and Engineering Research Council of Canada (NSERC). The loan of ,and support for, the EM3002 system was provided by Kongsberg Simrad USA The provision of the MV 321 for the 2 week period was donated by the National Park Service.
Ferrari, R., 1988, 1986 LAKE POWELL SURVEY: U.S. Department of the Interior, Bureau of Reclamation, REC-ERC-88-6, 67pp.
Condit, W., Drake, C.L., Mayer, L. and Spydell, P., 1978, Sedimentation in Lake Powell: Lake Powell Research Project Bulletin, # 64, National Science Foundation.
website, survey and processing by: Hughes Clarke and Beaudoin, OMG, UNB - May 2005