Visual OTTHYMO

Visual OTTHYMO (VO) is a hydrologic modeling platform designed for simulating single-event and continuous rainfall and snowmelt runoff across urban and rural watersheds. Originally derived from the USDA HYMO model and tailored for Canadian municipal engineering practice, the software uses object-oriented schematic modeling to compute and route hydrographs through subcatchments, channels, pipes, reservoirs, wetlands, and low-impact development (LID) controls. It incorporates flow-generation modules such as STANDHYD, NASHYD, WILHYD, and SCSHYD to calculate runoff hydrographs based on unit hydrograph theory and regional hydrologic methods.

Practicing water resources engineers reach for Visual OTTHYMO to prepare master drainage plans, evaluate pre- versus post-development runoff, size stormwater detention ponds, and perform water balance assessments for regulatory approvals. Its schematic visual editor and parameter-efficient commands speed up model construction and review compared to full hydraulic solvers. However, the software requires a paid commercial license, is available only on Windows desktop, and is primarily tailored to Canadian regulatory standards and HYMO-based regional methodologies.