Flood Risk and Vulnerability Analysis Project - Atlantic Climate ...

determination of the degree and nature of instability, including watercourse changes and also
quantification of active channel widths and gravel area, braiding indices, sinuosity and channel
occupancy indices. Identification of meanders and related alternation of pool-riffle sequences
controlling the local distribution of bank erosion can also enable construction of a channel
migration zone (CMZ) hazard map. Using raster-based GIS techniques, these data can then be
combined with measurements of distance from river channel and flood return periods, to create
a model which enables spatial mapping of river bank erosion probabilities (probabilities that can
then be mapped for hypothetical floods of, for example, 10 and 25 year recurrence interval).
In the initial stages of this analysis, however, three key reasons were identified why the above
approach would not be practical for this study.
Firstly, this assessment was to be founded upon the satellite imagery that was acquired to
support the land classification and change detection analysis which is also a component of this
project. The initial investigation of the quality of available satellite data for the initial period
(Earth Observation for Sustainable Development of Forests [EOSD] data which was generated
from 30-meter Landsat satellite imagery from the year 2000) for this project indicated that the
spatial resolution of the imagery would not support useful interpretation and delineation of most
of the channels under scrutiny, i.e., the satellite imagery is too coarse to resolve subtle changes
in the bank changes of quite narrow rivers. Use of aerial imagery may have improved the spatial
resolution issue, but this approach was beyond the current project scope given the cost and
effort involved to acquire and process the large number of images required to support analysis
of even a single reach of watercourse.
Secondly, the geomorphologic context of many streams in the study is incised bedrock,
meaning the importance of meandering is relatively insignificant compared to, for example, a
dynamic gravel bed river in the Canadian Rockies.
Thirdly, we recognized that although this type of analysis might be worthwhile in a more detailed
study (e.g., Phase II study), for this project the details obtainable using this approach would not
be commensurate with the overall more general methodology developed for this prioritization
analysis.
4.2 Prioritization Analysis
The overall results are summarized in an Excel spreadsheet based decision matrix outlining
community ranking based on the prioritization parameters previously outlined. One additional
consideration was integrated into the analysis at this stage, namely, the hierarchy of
prioritization parameters. In other words, the concept that some of the parameters used for
prioritization are more important for the analysis than others. In review of the parameters, some,
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