3.4 Connectivity Regimes
Across the 2018 study period, sites identified as stable
(Cdur = 0% or 100%; Outflow, Main-Mid, & Pond-Iso)
had generally unimodal distributions of connectivity strength with modes
at high or low values (Figure 6). In contrast, distributions of
connectivity strength at the remaining seven sites with intermittent
connectivity, had wide spread and a dominant mode at lower connectivity
values and a secondary mode at high connectivity values (Figure 6).
Within the intermittent target sites, some sites such as Side-03 and
Pond-Con-02 exhibited rapid shifts between modes with few observed
sample dates with intermediate connectivity strength while others
including Pond-Con-01, Side-01, and Side-02 exhibited more gradual
behavior with intermediate connectivity strength values for a larger
proportion of the study period (Figures 3 & 6).
Aggregating site specific results to the river-floodplain system reveals
transitions in system connectivity. At high flows, conditions are more
homogenous and there is relatively high connectivity across the entire
river-floodplain system (Figure 7a & b). Conversely, there was a
bimodal distribution of river-floodplain connectivity at lower flows
with some sites remaining connected and others becoming disconnected
from Inflow. The mean value of σm across the
river-floodplain system was positively related to Inflow stage (Figure
7c), whereas the variance in connectivity, as derived from the standard
deviation of σm, was highest during intermediate flows
(Figure 7d).
At the river-floodplain system scale, we also found that defining binary
σm connectivity thresholds to describe the system wide
behavior can be sensitive to the chosen σm threshold
value (Figure 8). We varied the threshold between the 10th to 90th
percentiles of σm and observed the effect on exceedance
probabilities of how many sites are connected in the 2018 study period.
Varying σm thresholds between 0.4 to 0.6 generated small
shifts in the exceedance probabilities distributions. Outside that
range, exceedance probability distributions exhibited larger changes in
their shape (Figure 8).