2.5.1 Synthetic experiment
The importance of re-infiltration in principle is governed by (1) soil
properties, (2) soil water saturation, and (3) excess rainfall rates. To
quantify the relative importance and generalize our results, we decide
to conduct a sensitivity test in this study area to mimic different
environment while preserving other variables. The sensitivity analysis
addresses the following hypotheses: 1) discernable differences exist
when switching on and off re-infiltration scheme, 2) re-infiltration
alters flood inundation magnitude and dynamics, and 3) differences are
amplified when increasing soil infiltration rates and drying antecedent
soil saturation. Of five hydrologic parameters, we select two soil
parameters (i.e., Ksat and B) that have a direct interaction with
infiltration rates. Increase in Ksat and B promote re-infiltration
amount. Additionally, the antecedent soil moisture
(SM0), proven to be critical for flood generation (Li et
al., 2021b; Yang et al., 2011), is another term to change infiltration
dynamics: higher soil water saturation results in less re-infiltration.
We applied a multiplier to each parameter of interest, ranging from 0.0
to 2.0 with 0.1 spacing except for SM0 that only ranges
from 0.0 (completely dry) to 1.0 (fully saturated) with 0.1 spacing.
For the forcing data in this experiment, we consider a 100-year extreme
in the study area by looking up the local Intensity-Duration-Frequency
table. This determined rainfall rates are uniform across 2 hours without
spatial heterogeneity to eliminate the impact of rainfall spatial
structure because we solely consider the impact by soils. We run the
model for 24 hours for each parameter, totaling 50 runs.