6. Hydrograph Reconciliation

We have estimated flood flows using both WINFAP (peak flow only) and ReFH (peak flows and hydrographs).  Generally we would apply full hydrographs to flood models, but often reconcile hydrographs with WINFAP peak flow estimates in accordance with current guidance.

The "Hydrograph Library" tab provides the functionality to reconcile flow estimates and apply climate change uplifts to our hydrographs.

As we create a new hydrograph library, we note that our preferred ReFH2 analysis, and preferred (only, in this case) WINFAP analysis have been selected automatically, though the user should select an appropriate statistical distribution (e.g. GL, GEV, KAP3). We ensure we provide comments to explain the reasoning for using a specific analysis. We also note the original (unmodified) URBEXT2000 value is provided for information. 

We want to add scaling to account for climate change, and amend the site region from Wales to England so the correct climate change uplift factors are available for use. In this example we apply the "2050s upper" allowance.

We also create a second set of hydrographs using the other ReFH2 analysis with the different storm duration. Both hydrographs are provided with meaningful names and descriptions.

User Steps: Add a hydrograph to the library using one of the ReFH2 analyses. Add a climate change uplift of 1.52 by using the default 2050s upper (hint - you will need to change the CC uplift are to England). Save the hydrograph. Then add a second hydrograph to the library using the other ReFH2 analysis (63hr storm duration). 

More information on the tool and climate change allowances is provided in the technical reference section.