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

Watershed Slope
The slope attribute associated with the soils data were used to determine an approximate
average slope across a watershed. In a manner similar to drainage density, higher average
watershed slope can suggest both higher runoff rates and a more 'flashy' hydrograph.
The prioritization weighting will reflect the watershed slope as follows:
Weighting Description
0 If the average slope is less than or equal to 5%
1 If the average slope is greater than 5% and less than or equal to 15%
2 if the average slope is greater than 15%
Deforestation
Table 4-6. Watershed Slope Weighting
Watershed runoff response will be influenced by changes in land cover as a result of community
development. The change detection analysis completed as a component of the land
classification analysis was used as the basis for this aspect of the assessment. The prioritization
weighting was assigned as the combined “deforested to developed” plus “deforested to other”
change detected.
Broader changes in land cover as a result of changing terrestrial communities due to climate
change are addressed in Vasseur and Catto (2008). However, the sensitivity and vulnerability of
forest communities in Atlantic Canada is considered to be low to moderate. Further, given that
the Vasseur and Catto (2008) assessment of climate change influences on forest systems
provided no specific guidance on regional variation of potential impacts across the Province,
there was not any means of using this issue as a prioritization factor in the present assessment.
4.1.11 Watercourse Hydraulics
It was originally proposed to investigate potential changes to hydraulic response via co-analysis
of a time series of (satellite) imagery available over a common location, interpretation of which
might allow for identification of physical changes in the thalweg and banks of a watercourse
indicative of channel forming flows during the periods between image acquisitions. This now
commonly applied GIS methodology uses heads-up digitizing by a trained geomorphologist to
delineate channel planform (active channel boundaries) as depicted and interpreted in a series
of co-registered high resolution satellite images and/or aerial photographs. These are then
overlaid in GIS to study recent channel change (e.g., 1980, 1990 and 2000) with the goal of
capturing the impacts of at least one significant flood. Once recent river planform changes on
the study reach have been identified, stable and unstable reaches can be defined allowing the
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