Large Scale Municipal Flood-Mapping in Northern Nova Scotia with PCSWMM, HEC-RAS and In-house Automated Tools

Flood maps provide critical information on flooding impacts and risk to coastal and riverine areas, and aid vulnerable communities with planning and emergency response. CBCL has been involved in the Municipal Flood line Mapping efforts in Nova Scotia from the beginning, aiding in the development of technical specifications. This presentation outlines a large-scale municipal flood-mapping project in Northern Nova Scotia. The project includes components such as stakeholder engagement, data collection and processing, hydrologic modelling in PCSWMM, in-house tools to facilitate the process, hydraulic modeling using HEC-RAS and flood mapping results and interpretation. This presentation will focus on the hydrologic analysis portion of the project, which was optimized through the development of in-house tools made to automate the process, streamline data input, and enhance the accuracy of model parameters. Hydrologic analysis in PCSWMM simulates runoff response based on watershed characteristics (e.g., land cover, soil infiltration, slopes) and expected rainfall under both current and climate change conditions. A key complexity of the study area was that various parts showed very different hydrologic responses, which necessitated the use of more than one flow gauge for calibration. The process of identifying representative flow gauges for the various parts of the study area was automated using a Python Script developed in-house. The script reads land cover and soils information, and automatically produces a table with calculated percentages of each land cover and soil type for specified watersheds, saving hours of time in GIS analysis. Overall, this presentation aims to demonstrate the need for innovations in large-scale flood mapping projects to improve the efficiency and accuracy of the results, ultimately facilitating decision-making and improving flood risk management