From Fread, D.L., Flood routing models and the Manning n

Calibration Objectives

• Develop an accurate representation of the physical system

• Match observed stages and discharge as closely as possible

• Maintain computational stability over a wide range of hydraulic conditions

Bullets adapted from RTi (2007) Report on “Calibration for the Lower Tar River Basin”

Additional Calibration Tips• Calibrate for at least 2 years of data if possible.

Additionally, calibrate drought and historic peak conditions if possible*

• Check water balance on total inflows and outflows. If not within 5-8%, local ungaged flows need to be modified.*

• When possible, focus on events where you have confidence that ungauged flows from the hydrologic models are correct (use observed flow data where it is available)**

• See next slide with pointers on decomposing a river system into calibration reaches

• When roughness as a function of flow, be aware that drastic changes in roughness from one interval to the next can result in model stability problems

* From NWS Notes by Janice Sylvestre** From RTI (2007) “Calibration for the Lower Tar River Basin”

Fread and Smith (1978) suggest calibration from upstream to down stream

Decomposing a river system for calibration

Fread, D.L., Smith, G.F., Calibration Technique for 1-D Unsteady Flow Models, Journal of the Hydraulics Division, 1978.