ReFH Urban Method (Revised ReFH Rainfall-Runoff Method)

Time step

Time interval used in unit hydrograph and rainfall profile (hrs).

∆t

-

>0

α Factor Method

a_T calculation option ('DESIGN' or 'USER').

If set to 'DESIGN' then the a_T value is calculated by Flood Modeller by interpolating for the given return period from a lookup table of a_T values against return periods for the given season. Note that the season is obtained from the value set by SEASONFLAG.

If set to 'USER', the input value of a_T is used.

ALPHAFLAG

DESIGN

α Factor

Initial soil moisture correction factor. (only used if ALPHAFLAG is set to 'USER').  

ALPHA (aT)

1

0 < aT ≤ 1 if ALPHAFLAG='USER'

ARF

Areal reduction factor to relate point rainfall to areal rainfall. Range 0.0 to 1.0. The input value of arf is ignored and calculated internally if ARFFLAG is set to 'DESIGN'.

arf

-

0 < arf ≤ 1 if ARFFLAG='USER'

Areal Reduction Factor Method

ARF calculation option ('DESIGN' or 'USER').

If set to 'DESIGN' then the areal reduction factor is calculated by Flood Modeller as a function of STAREA and STDUR from a digitised form of Figure 3.4 in the FEH Volume 4. If STAREA is set to zero then CAREA is used.

If set to 'USER', the input value of arf is used.

ARFFLAG

DESIGN

BF₀

Initial Baseflow (m³/s). The input value of BF₀ is ignored and calculated internally if BF0FLAG is set to 'DESIGN'.

BF0

0

>0 if BF0FLAG='USER'

BF₀ Calculation Method

Baseflow calculation option ('DESIGN' or 'USER').

If set to 'DESIGN' then the initial baseflow is calculated by Flood Modeller as a function of CINI, SAAR and [catchment] AREA.

If set to 'USER', the input value of BF₀ is used.

BF0FLAG

DESIGN

BFIHOST

Baseflow index catchment descriptor

BFIHOST

-

Simulation Type

Flow values to use during simulation, can be one of:

    'base flow ('bfonly')

    'peak flow' ('pfonly')

    'full hydrograph' (null, default)

For example, if 'base flow' is selected then the baseflow contribution is used for the boundary flow value for the  simulation.

bfonly

<blank>

B_L

Baseflow lag (hrs, only used if BLFLAG is set to 'USER').

BL

>0 if BLFLAG='USER'

B_L Donor Correction Factor

Baseflow lag donor correction [multiplicative] factor.

BLDCF

1

>0

B_L method

Baseflow lag (B_L) calculation option ('DESIGN' or 'USER').

If set to 'DESIGN' then the BL is calculated by Flood Modeller as a function BFIHOST, PROPWET, URBEXT and DPLBAR.

If set to 'USER', the input value of B_L is used.

A donor correction factor may also be applied to the calculated value of B_L.

BLFLAG

DESIGN

B_R Method

Baseflow recharge (only used if BRFLAG is set to 'USER').

BR

>0 if BRFLAG='USER'

B_R Donor Correction Factor

Baseflow recharge donor correction [multiplicative] factor.

BRDCF

1

>0

B_R Calculation Method

Baseflow recharge (B_R) calculation option ('DESIGN' or 'USER').

If set to 'DESIGN' then the B_R is calculated by Flood Modeller as a function BFIHOST and PROPWET.

If set to 'USER', the input value of B_R is used.

A donor correction factor may also be applied to the calculated value of B_R.

BRFLAG

DESIGN

c

Catchment descriptor - DDF model parameter c.

c

-

Calibration Factor

Calibration factor applied to each sub-hydrograph 1: unpaved 2: urban, drain away; 3: urban, drain towards

calib(i)

1

Real.

>0

Area

Contributing catchment area (km²)

CAREA  

-

>0; warning if area < 0.038 or  area > 9868

C_ini

Initial soil moisture content (mm, only used if CINIFLAG is set to 'USER').

CINI

>0 if CINIFLAG='USER'

C_ini Method

CINI calculation option ('DESIGN' or 'USER').

If set to 'DESIGN' then the CINI value is calculated by Flood Modeller as a function C_MAX, BFIHOST and PROPWET for the current season (defined by SEASONFLAG).

If set to 'USER', the input value of C_INI is used.

CINIFLAG

DESIGN

C_max

Maximum soil moisture capacity (mm, only used if CMAXFLAG is set to 'USER').

CMAX

>0 if CMAXFLAG='USER'

C_max Method

CMAX calculation option ('DESIGN' or 'USER').

If set to 'DESIGN' then the C_MAX value is calculated by Flood Modeller as a function BFIHOST and PROPWET.

If set to 'USER', the input value of _CMAX is used.

A donor correction factor may also be applied to the calculated value of C_MAX.

CMAXFLAG

DESIGN

C_max Donor Correction Factor

C_MAX donor correction [multiplicative] factor.

CMDCF

1

>0

d1

Catchment descriptor - DDF model parameter d1.

d1

-

d2

Catchment descriptor - DDF model parameter d2.

d2

-

d3

Catchment descriptor - DDF model parameter d3.

d3

-

DPLBAR

Mean drainage path length catchment descriptor (km)

DPLBAR

-

>0

DPSBAR

Mean drainage path slope catchment descriptor (m/km)

DPSBAR

-

>0

e

Catchment descriptor - DDF model parameter e.

e

-

Easting

Easting coordinate of catchment outflow (not used in calculations)

easting

0

Rainfall Flag

Event rainfall calculation option Design Rainfall or Observed (ERFLAG='DESIGN' or 'USER').

If set to 'DESIGN' then the DDF model, SCF and ARF are combined to give a rainfall depth.

If set to 'USER', the input value of precipitation is used.

ERFLAG

DESIGN

For METHOD='DLL', only 'DESIGN' is possible

f

Catchment descriptor - DDF model parameter f. Only used if ERFLAG = 'USER', the remainder only if ERFLAG = 'DESIGN'.

f

-

Boundary Type Flag

Boundary mode flag: 'HYDROGRAPH' denotes a generated hydrograph (i.e. the unit behaves as a QTBDY); 'HYETOGRAPH' indicates that it behaves as a REBDY-type unit, applying the Rainfall profile to a Rainfall-Only boundary (the latter must be used in conjunction with lateral inflow unit)

hymode

HYDROGRAPH

Node Label

Node label identifier

Label

-

Loss to sewers

Determines whether urban sewer loss is by volume or flow rate.

Loss_by

'VOLUME'

'VOLUME' or 'FLOW'

Calculation Source Flag

Calculation method - determines whether the WHS dll ('DLL') or the 'hardcoded' method from the published report ('REPORT') is used for calculations.

METHOD

'DLL'

'DLL' or 'REPORT'

Minimum Flow

Minimum flow (m³/s). Usually zero. Forces the resultant hydrograph to be not less than the specified flow. This may be required for program stability

minflow

0

≥0

Northing

Northing coordinate of catchment outflow (not used in calculations)

northing

0

n/a

Number of rainfall profile values

nrp

0

>0 if RPFLAG='USER'

n/a

Number of unit hydrograph ordinates. May equal zero if UHFLAG = 'DESIGN'.

nuh

0

>0 if UHFLAG='USER'

Observed Rainfall Depth

Event rainfall precipitation (mm). This is deemed to include any seasonal or areal correction factors.

Only used if ERFLAG is set to 'USER'.

P

0

>0 if ERFLAG='USER'

PROPWET

Catchment descriptor - proportion of time catchment soil moisture deficit (SMD) was below 6mm during the period 1961-1990. (range 0.0 - 1.0)

PROPWET

-

0 ≤ PROPWET≤ 1

Observed Rainfall: Rainfall

Rainfall profile starting at tstart with data interval t (mm)

rp

-

≥ 0 if RPFLAG='USER';

Σrp=P

Sewer Capacity

Return period (yr) or depth (mm) value used in calculating drainage capacity of sewers draining away from the watercourse

RPDvalue

10

Real.

≥0 (depth)

>2 (return period)

n/a

Rainfall profile option ('DESIGN' or 'USER').

If set to 'DESIGN', then the standard rainfall profile for the current season (50% summer or 75% winter) is used.

If set to 'USER', the input values of the rainfall profiles are used.

RPFLAG

'DESIGN'

For METHOD='DLL', only 'DESIGN' is possible. Value written automatically by the UI, dependent on ERFLAG

Use refined rainfall profile

If checked (refine rp=1), uses a finer discretisation of the standard FSR rainfall profiles - can prevent 'blocky' rainfall profiles for long storm/short data interval events

refine_rp

1

0 to 1

Sewer Capacity: Flag/Value

[Urban ReFH] Flag to denote whether return period (rpordepth='RETURN') or depth (rpordepth=‘DEPTH’) is being used in calculating drainage capacity of sewers draining away from the watercourse. The value entered is either the return period (yr) or rainfall depth equivalent (mm).

RPorDEPTH, RPDvalue

‘RETURN’

‘RETURN’ or ‘DEPTH’ only

Season Flag

Season flag - 'SUMMER', 'WINTER' or 'DEFAULT'. If set to 'DEFAULT', then WINTER applies if URBEXT<0.125; SUMMER otherwise.

Uses the design rainfall profile (50% summer or 75% winter), SCF, C_INI, a_T and BF₀ values for the season, where appropriate.

75% winter and 50% summer profiles are taken from Figure 3.5 in FEH Volume 4

SEASONFLAG

DEFAULT

SAAR

Standard annual average rainfall (mm) - catchment descriptor.

SAAR

-

>0

Hydrograph Scaling Method: Scale

Hydrograph scaling method FULL (scaling = 'FULL': default) scales the whole hydrograph; Quick Runoff (scaling='RUNOFF'): scaling only applies to the quick runoff component of the hydrograph..

Used in conjunction with SCFLAG and scfact.

SCALING

'FULL'

method

Hydrograph scaling option. By a factor of (’scflag='SCALE' [default]) – applies the specified factor; To fit peak of (scflag='PEAK') – fits the hydrogrpah peak to the specified value.

SCFLAG

1

>0

If SCFLAG='PEAK' then all hydrograph ordinates are scaled (by a constant value) to achieve a peak flow of scfact.

If SCFLAG='SCALE' then all hydrograph ordinates are multiplied by scfact (default is 1.0).

scfact

Seasonal Correction Factor (SCF)

Seasonal correction factor applied to the DDF rainfall (along with ARF) to derive the design rainfall (only used if SCFFLAG is set to 'USER').

SCF

1

>0 if SCFFLAG='USER'

Seasonal Correction Factor Flag

SCF calculation option ('DESIGN' or 'USER').

If set to 'DESIGN' then the SCF is calculated by Flood Modeller as a function SAAR and the storm duration for the current season (as given by SEASONFLAG).

If set to 'USER', the input value of SCF is used.

SCFFLAG

DESIGN

Snow Melt Rate

Rate of snowmelt (mm/day). Not used (yet) in ReFH.

SNRATE

0

≥0

Storm Area

Storm area (km2). This is used only in calculating ARF (and has no effect on the rainfall volume); if STAREA is entered as zero or negative then STAREA is set to CAREA

STAREA

0

For METHOD='DLL', this is not active

Storm Duration

Storm duration (hrs). Should be the nearest odd integer multiple of ∆t.

STDUR

-

>∆t

Area for subarea

Subcatchment area (km²) for subareas:

1: unpaved;

2: urban, drain away;

3: urban, drain towards

SUBAREA(i)

0?

Real.

≥0

DPLBAR for subarea

DPLBAR (mean drainage path length, km) value for subareas:

1: unpaved;

2: urban, drain away;

3: urban, drain towards

SUBDPLBAR(i)

0

Real.

≥0

BR (for subarea)

Baseflow recharge parameter for subareas:

1: unpaved;

2: urban, drain away;

subbr(i)

-

Percentage Runoff value for subarea

Percentage value for subareas:

2: urban, drain away;

3: urban, drain towards

subpr(i)

70

Real.

0<subpr≤100

NB There is no subpr(1)

URBEXT1990 for subarea

URBEXT1990 value for subareas:

1: unpaved;

2: urban, drain away;

3: urban, drain towards

SUBURBEXT(i)

(0, 0.5, 0.5)

Real.

[0,1].

Return Period

Return period (years)

T

-

>1; warning if T>150

Time Delay

Optional delay time (hrs), e.g. if tdelay=2hrs then the hydrograph will start 2hrs after the start time of the simulation.

tdelay

0

T_p

Time to peak of instantaneous unit hydrograph (hrs)

Tp0

-

>0 if TPFLAG='USER'

T_P donor correction factor

TP donor correction [multiplicative] factor.

TPDCF

1

>0

T_p method

Unit hydrograph T_p option ('DESIGN' or 'USER'). If set to 'DESIGN', T_p is calculated using catchment descriptors; if set to 'USER', the user input value of T_p is used.

TPFLAG

DESIGN

Time to peak of t-hour unit hydrograph (hrs) - not currently used

TpT

-

n/a

Unit hydrograph ordinates with data interval D_t (see units); only used if UHFLAG is set to 'USER'. (Not accessible from the user interface).

uh

-

≥0 if UHFLAG='USER'

n/a

Scaling factor for the unit hydrograph ordinates. Only used if the 'units' keyword is not recognised. If zero or blank then units of m³/s/mm are used. (Not accessible from the user interface.)

uhfctr

0

n/a

Unit hydrograph option ('DESIGN' or 'USER'). If set to 'DESIGN' then the ReFH design 'kinked-triangle' unit hydrograph is used, using T_P, U_c and U_P.

If set to 'USER', the input values of the unit hydrograph are used.(Not accessible from the user interface).

UHFLAG

DESIGN

U_k

Dimensionless instantaneous unit hydrograph 'kink' facto the multiplier applied to U_C, the triangular U_H ordinate at time 2TP. NB If U_k = 1, then a triangular unit hydrograph results.

Only used if UKFLAG is set to 'USER'.

Uk

0.8

>0 if UKFLAG='USER'; also cannot allow UH time base to be < 2Tp

U_k Method

Uk calculation option ('DESIGN' or 'USER'). If set to 'DESIGN' then the standard factor of 0.8 is used.

If set to 'USER', the user input values of U_k is used.

UKFLAG

DESIGN

Units

Units of the unit hydrograph ordinates. Keyword can be one of:

• 'cm100k': 1cm depth over 100km² (units = m³/s/cm/100km²)
• 'cmarea': 1cm depth over catchment area (units = m³/s/cm)
• 'mm100k': 1mm depth over 100km2 (units = m³/s/mm/100km²)
• 'mmarea': 1mm depth over catchment area (units = m³/s/mm)

NB The conventional units often used are m³/s /cm/100km² (Not accessible from the user interface)

units

'mmarea'

U_p

Dimensionless instantaneous unit hydrograph ordinate at time to peak. Only used if UPFLAG is set to 'USER'.

UP

0.65

<2 if UPFLAG='USER'

U_p Method

U_P calculation option ('DESIGN' or 'USER'). If set to 'DESIGN' then the standard value of 0.65 is used.

If set to 'USER', the user input values of U_P is used.

UPFLAG

DESIGN

Use Urban subdivisions

Flag to denote if Urban ReFH variation is being used (Urban=‘URBANREFH’ if true)

Urban

<blank>

Blank, or ‘URBANREFH’.

NB Any other value is interpreted as blank

URBEXT

Extent of urban/suburban land cover (range 0.0 - 1.0) - catchment descriptor.

NB The value of URBEXT affects the default season, i.e. if SEASONFLAG is set to 'DEFAULT', i.e. summer applies if URBEXT ≥ 0.125; winter otherwise.

URBEXT

-

0 ≤ URBEXT ≤ 1

n/a

Elevation (mAD). Not used in ReFH calculations.

z

0