Beaver Dam Hydrograph: 2D Cross-Section & Water-Balance Model

This is the 2D counterpart to the 3D beaver-dam scene, and it reaches the same result through a genuinely different visual mechanism while solving the identical equations. Instead of an orbiting 3D pond cascade with instanced flow particles, this version draws a stream-profile cross-section — three ponds stacked immediately upstream of their dams, each filled to a depth solved from a real water-balance ODE (weir overflow above crest, porous leakage through the dam body, Darcy-style seepage into the banks) — paired with a live hydrograph strip chart plotting inflow against downstream discharge over time, the standard way hydrologists actually read flood attenuation off a chart. Adjust the dam crest height, bank permeability and storm intensity, trigger a storm pulse, and toggle the dams off entirely to watch the undammed channel pass the same flood straight downstream with no attenuation and no rising water table.