Hydrology tab
  • 08 Aug 2022
  • 5 Minutes to read
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Hydrology tab

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The Hydrology Tab contains buttons for insertion of hydrological boundaries into 1D Network Models and also provides access to some hydrological analysis tools.

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General hydrology

Rainfall/Evaporation Boundary

This button adds a Rainfall Evaporation boundary unit (REBDY) to your 1D network or event file (either directly or by then clicking on the map to locate your node). After specifying the name of your unit an interface is displayed to enable you to define an inflow boundary to your model based on any combination of rainfall, evaporation or infiltration data. This unit is useful where direct rainfall or evaporation forms a significant proportion of the water volume entering a system.

Generic Rainfall-Runoff Boundary

This button adds a Generic event Rainfall-Runoff boundary unit (GERRBDY ) to your 1D network or event file (either directly or by then clicking on the map to locate your node). After specifying the name of your unit an interface is displayed to enable you to define a hydrological inflow boundary. The unit provides multiple options for each hydrological component within your boundary unit. The currently implemented models focus on the globally-applicable SCS (US Soil Conservation Service) model, the Green-Ampt loss model (an observed rainfall model) and simple constant and recession baseflow models.


Specific hydrology

Flood Estimation Handbook Rainfall Runoff Method (FEH) Boundary

This button adds a boundary unit to your 1D network or event file that utilises the Flood Estimation Handbook Rainfall Runoff Method to define an inflow (FEHBDY). After locating your unit (on the map or in the network table) and specifying the name of your unit an interface is displayed to enable you to define this hydrological inflow boundary.

Revitalised Flood Hydrograph Rainfall-Runoff (ReFH) Boundary

This button adds a boundary unit to your 1D network or event file that utilises the Revitalised Flood Hydrograph Rainfall-Runoff Method to define an inflow (ReFHBDY). After locating your unit (on the map or in the network table) and specifying the name of your unit an interface is displayed to enable you to define this hydrological inflow boundary.

2016 Revitalised Flood Hydrograph Rainfall-Runoff (ReFH2) Boundary

This button adds a boundary unit to your 1D network or event file that utilises the 2016 version of the Revitalised Flood Hydrograph Rainfall-Runoff Method to define an inflow (ReFH2). After locating your unit (on the map or in the network table) and specifying the name of your unit an interface is displayed to enable you to define this hydrological inflow boundary.

Flood Studies Supplementary Reports (1977-1988) Number 16 Method (FSSR16) Boundary

This button adds a boundary unit to your 1D network or event file that utilises the FSSR16 Method to define an inflow (FSSR16BDY). After locating your unit (on the map or in the network table) and specifying the name of your unit an interface is displayed to enable you to define this hydrological inflow boundary.

Flood Frequency Simulation (FRQSIM) Boundary

This button adds a boundary unit to your 1D network or event file that utilises the FRQSIM Method to define an inflow (FRQSIM). After locating your unit (on the map or in the network table) and specifying the name of your unit an interface is displayed to enable you to define this hydrological inflow boundary.


Hydrology tools

Optimised Storm Duration

The Optimal Storm Duration (OSD) tool enables you to find this optimal storm duration for a model containing one or more catchment inflow hydrograph units. It automatically sets up and manages multiple model simulations to find the optimal storm duration without requiring you to prepare individual model files for each run (each using different storm durations) or to add these to a batch simulation.

Current compatible units are FEH boundary (FEHBDY), FSSR16 boundary (FSSR16BDY) and ReFH boundary (ReFHBDY). The tool varies storm duration in a selection of 1D simulations in which all other model settings (including all other hydrological unit parameters) remain the same. The default optimisation algorithm used to select storm durations is Brent's method (e.g. Press W.H. et al (1986)), which will home in on the optimal point significantly quicker than either an exhaustive search or a successive interval halving method. An exhaustive search is also available as an alternative option.

Accessing the tool will display a new window into which your currently active 1D network will be loaded automatically (a 1D network is required in order to use the tool). You can then specify which boundary units to analyse and where in your model you wish to optimise for maximum flows or levels.

The tool will automatically run multiple simulations to determine an optimal solution. All results are displayed in both tabular and graphical forms. After using the tool it is the modeller’s task to then update their model accordingly to incorporate the optimal settings recommended by the tool.

Probabilistic ReFH
One of the greatest sources of uncertainty in hydrodynamic model outputs is associated with estimating hydrological inputs in ungauged locations. The Probabilistic ReFH tool can be used to quantify uncertainty in ReFH hydrological boundaries. It uses a stratified uncertainty analysis applied to ReFH model parameters to illustrate how uncertainty in inputs propagates through to uncertainty in model outputs, in this case hydrograph generation. In a staged analysis, a sub-set of ReFH hydrographs are then typically routed through a hydrodynamic model in order to quantify uncertainty in the model results.

Accessing the tool will display a new window into which the compatible hydrological boundaries (ReFH only) within your currently active 1D network will be loaded automatically (a 1D network is required in order to use the tool).

Running the ReFH uncertainty analysis is a two-stage process within the Flood Modeller interface. The first consists of the generation of a number of hydrographs (defaulting to 33) which can then be ranked in order of peak flow, time to peak or flow volume in order to determine exceedence. From this, you can then select a smaller subset, for example based on required exceedence percentiles, for which to run a full hydrodynamic simulation. Uncertainty is therefore estimated by relating a percentage exceedence to model output.


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