CERC-HAND-D - A Tool for Supporting On-the-Fly Flood Mapping in Canada.

A custom ArcPro tool, the CERC-HAND-D tool, was developed to create synthetic rating curves (SRCs) using accessible data in Canada. SRCs could support the integration of the Height Above Nearest Drainage (HAND) model into an On-The-Fly flood mapping application for a Canada-wide service. A challenge with creating SRCs is finding an accurate method of representing multiple surface roughness coefficients ( $n$ ) present in a study area. Two distributed $n$ methods were experimented with (a weighted method and a minimum-median method) and were compared to a fixed single $n$ method using CERC-HAND-D. Control data was sourced from gauge stations across Eastern and Central Canada. Results indicate that in areas with medium to medium-high river gradients $(\mathrm{S} > 0.002\ \ \mathrm{m}/\mathrm{m})$ and river lengths under 5 km, the CERC-HAND-D tool creates more accurate SRCs $(\text{NRMSE}=3.7\%-7.0\%, \text{Percent Bias} =-3.7\% -11.5\%)$ , with no $n$ method outperforming the other two.