Zhouyayan Li, Jerry Mount, Ibrahim Demir

In this study, the performance of Height Above Nearest Drainage (HAND) was evaluated in Linn, Jones, Johnson, Cedar, and Muscatine counties in the State of Iowa. The impacts of three model parameters (drainage threshold, water depth, resolution of data) were studied. The effectiveness of improving approaches—variable water depths, community-level analysis, and inner zone was explored. The model performance was compared against flood hazard maps of 100- and 500-year flooding events generated by the Iowa Flood Center. Results showed the Hit Rate, Proportion Correct and Kappa Value reached 0.80 (0.79 for 500-year event), 0.93, and 0.69 (0.70 for 500-year event) respectively, even when no improving approach was involved. The approaches helped Hit Rate improve to 0.88 for both flooding events, and Mixed Index increase by 5.83 % (100-year event) and 5.77 % (500-year event). The study presented how to improve the accuracy of HAND model in a simple and practical way.