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.