5. CONCLUSIONS
This study focuses on the influence of the re-infiltration process for
100-year and 500-year flood events, which has so far not been
well-recognized by the hydrologic/hydraulic modeling community. The
sensitivity experiment and a 500-year Hurricane Harvey example both
highlight the discernable differences between the with and without
re-infiltration scheme. The major conclusions are summarized as follows:
1. In the 100-year design rainfall event, re-infiltration is found to
make discernible differences with less flood extent
(~1.56 km2), depth (~3
m), and dynamics (~4-hour delayed flooding and
~4-hour shorter inundation duration), compared to
without re-infiltration. The 500-year Hurricane Harvey event shows a
magnified difference in inundation duration up to 15 hours because of
the longer event duration. However, the flood depth difference is less
in the Harvey event due to the rapid saturation of the soils.
2. The hydraulic conductivity and antecedent soil condition from the
designed sensitivity test are found to be the prime contributors to the
difference between with and without re-infiltration, and comparatively,
the antecedent soil moisture condition is the most sensitive among the
three tested factors.
3. For the Harvey event, the differences are verified with stream gauge
observations. On average, a 139.9% increase in NSE scores is found for
re-infiltration with respect to without it. The improvements are mostly
tied to better characterization of the recession limb after peak flow
while the peak flows are well-captured by both. The proxy data – USGS
High Water Marks – also indicate better performance with the inclusion
of the re-infiltration scheme, as the re-infiltration scheme presents a
17.2% less flood depth difference than the case without the
re-infiltration. The differences are further expected to enlarge for
less intensive events and regions with a higher percentage of permeable
soil media.
This study aims to raise attention to the important re-infiltration
process in coupled H&H flood modeling to provide more accurate flood
information, e.g., depth and timings. For future work, we will continue
improving the current CREST-iMAP model framework by incorporating flood
mitigation measures such as levees and dams into the system. Also, it is
critical to couple with the NWP model to advance flood prediction lead
time, which ensures more time for residents at risk to evacuate.