2 METHODOLOGY 2.1 OVERVIEW OF
FFR METHODOLOGY
The methodology to determine the connectivity and free-flowing status of rivers (or Free-flowing river assessment; FRA) is based on a global methodology developed by Grill. A Free-flowing River Assessment comprises six distinct steps (see Figure 3): First, an integrated definition of FFRs was developed according to multiple aspects of connectivity (step 1). Second, the major pressure factors that influence river connectivity were identified (step 2) using an extensive literature review, and data was collated for each factor. The six pressure factors that were identified include: (a) river fragmentation; (b) flow regulation; (c) sediment trapping; (d) water consumption; (e) road construction; and (f) urbanization. Next, proxy indicators were calculated (step 3) for each factor using data from available global remote sensing products, other data compilations, or numerical model outputs such as discharge simulations (see Table 1). The indicators that were chosen are expected to have a substantial influence on connectivity and can be generated using robust global data sets of sufficient quality and consistency between countries and regions. All indicators were calculated for every river reach of the river network. A river reach is defined as the smallest element in the river network and is the line segment A between confluences. Grill et al. adjusted the weighting of each pressure indicator adjusted iteratively in a set of scenarios using different thresholds guided by literature reviews and expert judgement. These scenarios were benchmarked by comparing the resulting FFRs against reported FFRs compiled from literature resources and expert inputs. The final selection of weightings was applied to a multi-criteria average calculation (step 4) to derive the Connectivity Status Index (CSI) for every river reach (step 5).
Free-flowing rivers definition based on connectivity Calculation of proxy indicators CSI (%)
100 99-95 94-90 89-80 79-60 <60
Connectivity Status Index (CSI)
Yes
1 2
Selection of pressure factors related to definition
4
Application of weighting model
6
Application of threshold
3
5
River reach CSI status above threshold (CSI > 95%)
River reach with good connectivity status (above CSI threshold)
No
River reach impacted (below CSI threshold)
Entire river before threshold from source to outlet? Yes
Free-flowing river
Figure 3: Conceptual overview of methodology by Grill et al.
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