Flood routing translates a known inflow hydrograph at one location to a predicted outflow hydrograph at a downstream point (or through a reservoir) by applying mass-balance (continuity) principles, optionally combined with a momentum equation for distributed (hydraulic) routing, to account for the storage and resistance effects the flood wave experiences as it travels. Lumped (hydrologic) routing solves the simple continuity relation "inflow minus outflow equals rate of change of storage" using an assumed storage-outflow relationship, producing characteristic peak attenuation and time lag in the routed hydrograph; this belongs to surface-water hydrology, extending the theory of catchment-scale flood estimation into the prediction of flood-wave propagation through reservoirs and channels.
Flood routing translates a known inflow hydrograph at one location to a predicted outflow hydrograph at a downstream point (or through a reservoir) by applying mass-balance (continuity) principles, o…