Monitoring riverbed topography by digital photogrammetry, with particular reference to braided channels / Stuart N. Lane, D. Murray Hicks, Richard M. Westaway.

By: Lane, S. N.
Contributor(s): Hicks, D. M. Darryl Murray, 1954-. (NIWA. Christchurch) | Westaway, R. M. (University of Cambridge, Dept. of Geography. Cambridge, UK).
Material type: materialTypeLabelBookSeries: NIWA technical report: 64Publisher: Wellington, N.Z. : NIWA, 1999Description: 20 pages : illustrations ; 30 cm.ISBN: 0478084870.ISSN: 1174-2631.Subject(s): RIVERBEDS | BRAIDED STREAMS | BOTTOM TOPOGRAPHY | MONITORING | PHOTOGRAMMETRY | NEW ZEALANDOnline resources: Click here for online access In: NIWA technical report In: NIWA technical reportSummary: Surveys of riverbed and channel topography are key requirements for effective river channel management. Historically, rivers in New Zealand have been monitored by using a series of re-surveyed cross-sections. However, the spacing between successive cross-sections and the frequency of re-survey are often determined by practical issues rather than consideration of the nature of channel change or uncertainty in the results. Digital photogrammetry represents a technique that may provide a cheaper, more efficient, and more accurate method of monitoring riverbed morphology, detecting river channel change, and so improving river channel management. This report focuses on the use of digital photogrammetry to provide topographic information for wide gravel-bed rivers by considering its application to specially flown imagery of the North Ashburton River. First, some fundamentals of digital photogrammetry are introduced. Next, some practical issues concerned with planning a photogrammetric project are discussed, including a consideration of the quality of topographic data obtained. Finally, a procedure for dealing with areas where there is water is described and applied to a reach of the North Ashburton River. Results are assessed in terms of point accuracy and reliability (with respect to water depth distribution and sediment storage). Overall, the results are found to be very encouraging, producing mean elevation errors over dry parts of the riverbed that are smaller than the average grain size of the riverbed material. In submerged areas, a systematic bias is found, but this is substantially reduced after application of the correction procedure. The photogrammetric output is also found to be ideally suited to river management applications such as habitat assessment and mean bed level calculations
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Item type Current location Call number Copy number Status Date due Barcode
JOURNAL JOURNAL WELLINGTON
JOURNALS
CORE NO. 64 1999 1 Available J00638
JOURNAL JOURNAL WELLINGTON
JOURNALS
CORE NO. 64 1999 2 Available J019638

Surveys of riverbed and channel topography are key requirements for effective river channel management. Historically, rivers in New Zealand have been monitored by using a series of re-surveyed cross-sections. However, the spacing between successive cross-sections and the frequency of re-survey are often determined by practical issues rather than consideration of the nature of channel change or uncertainty in the results. Digital photogrammetry represents a technique that may provide a cheaper, more efficient, and more accurate method of monitoring riverbed morphology, detecting river channel change, and so improving river channel management. This report focuses on the use of digital photogrammetry to provide topographic information for wide gravel-bed rivers by considering its application to specially flown imagery of the North Ashburton River. First, some fundamentals of digital photogrammetry are introduced. Next, some practical issues concerned with planning a photogrammetric project are discussed, including a consideration of the quality of topographic data obtained. Finally, a procedure for dealing with areas where there is water is described and applied to a reach of the North Ashburton River. Results are assessed in terms of point accuracy and reliability (with respect to water depth distribution and sediment storage). Overall, the results are found to be very encouraging, producing mean elevation errors over dry parts of the riverbed that are smaller than the average grain size of the riverbed material. In submerged areas, a systematic bias is found, but this is substantially reduced after application of the correction procedure. The photogrammetric output is also found to be ideally suited to river management applications such as habitat assessment and mean bed level calculations

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