Developed by T. Endreny at SUNY ESF in the Department of Environmental Resources Engineering
Fluvial Geomorphology
glossary | menu | Normal | lg | hc | 9.) Fluvial Geomorphological Applications in River Forecasting > FGM and Lag / K Model Routing Parameters
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FGM and Lag / K Model Routing Parameters

Yolo Bypass model

Routing at RFCs requires lag parameter adjustment to delay the inflow hydrograph and better model the timing of observed flood waves. The K parameter is adjusted to attenuate the lagged inflow hydrograph and create a well sized and timed outflow hydrograph matching the downstream observation.

Lag and K attenuation can be applied as a constant factor or as a variable factor, changing with inflow or outflow discharge, respectively. Caution must be given to ensure that with use of variable lag values the hydrograph does not have two discharges for a single time, a volume corruption, or a missed peak value.

K is given units of time, and its derivation is often given as a ratio of channel storage to discharge. It is related to the K value used in the Muskingum flood wave model.

Image courtesy of NOAA

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