From 1960 through as recent as 2018, tropical cyclones (TCs) have produced greater than 1000-year rainfalls over time periods ranging from 1 to 5 days for the states in Federal Emergency Management Agency Region IV (except Kentucky, where the TC rainfall of record produced between a 200- and 500-year rainfall event). Therefore, TC rainfall events have the potential to affect the tail of flood risk statistical distributions, even for inland states. For flood risk modeling purposes, it is important to be able to simulate expected TC rainfall from a joint distribution of parameters like TC track, size, and intensity. Four existing parametric models already attempt to predict rainfall hyetographs from these variables, and an evaluation of the storm-total precipitation fields produced by these models was completed in Brackins and Kalyanapu (2020). In this study, the rainfall from the parametric models serves as the precipitation forcing to a Hydrologic Engineering Center Hydrologic Modeling System (HEC-HMS) model of the Swannanoa River (HUC10 0601010506), a tributary of the French Broad in western North Carolina. The objective of the current study is to perform a case study using a HEC-HMS model of the Swannanoa River to determine if rainfall produced by four parametric TC rainfall models allows for sufficient representation of TC flood discharge. While Brackins and Kalyanapu (2020) demonstrated that the IPET (2006) model was the most skillful at reproducing storm-total precipitation for thresholds above 75 millimeters (3 inches), preliminary HEC-HMS results indicate that the IPET model suffers from serious limitations for weakening TCs which are sufficiently far inland.
REFERENCES Brackins, J.T., and Kalyanapu, A.J. (2020). “Evaluation of parametric precipitation models in reproducing tropical cyclone rainfall patterns”. J. Hydrol. 580. https://doi.org/10.1016/j.jhydrol.2019.124255 Interagency Performance Evaluation Task Force (IPET). (2006). “Performance evaluation of the New Orleans and Southeast Louisiana Hurricane Protection System draft final report of the Interagency Performance Evaluation Task Force volume VIII – engineering and operational risk and reliability analysis”. Available from: https://usace.contentdm.oclc.org/digital/collection/p266001coll1/id/2842