This Global Database allows the definition of any number of land uses. The actual land uses employed for a given simulation must be chosen from the 'Landuse List' button in the 'Water Quality' dialog under Job Control. The land use names are used as column headings in the tabular output.
This dialog is used in the calculation of dust and dirt buildup (and removal by street sweeping) for the land use. In turn, this is used in calculating pollutant concentrations, where pollutant buildup is specified by its concentration within the dust and dirt.
If none of the pollutants rely on the landuse to calculate pollutant buildup then the landuse data is not important.
Upper limit for the buildup of dust and dirt. The units for this parameter depend on the Buildup Dependency variable, as follows:
|Buildup Dependency||Unit for Dust and Dirt Limit|
|Curb Length||lb/(100 ft curb) [kg/(km curb)]|
For the Exponential or Michaelis-Menton formulations, this value becomes the asymptote; for the Power-Linear form, this limit is imposed.
This parameter defines the dependent variable 'X' in the buildup equations formulated in this dialog. Dust and dirt buildup can depend on the subcatchment area, curb length, or neither (the value of 'X' is always 1.0 in this case).
Buildup by Catchment Area (J2 - JACGUT = 1)
Dust and dirt buildup is calculated using the landuse area (subcatchment area or part thereof).
Constant Buildup (J2 - JACGUT = 2)
Dust and dirt accumulates at the same rate regardless of the size of the subcatchment.
Buildup by Catchment Curb (Kerb) Length (J2 -JACGUT = 0)
Dust and dirt buildup is calculated using the curb (kerb) length entered for the subcatchment, in units of 100 ft [km]. The following table (American Public Works Association, 1969) displays measured accumulations of dust and dirt for the Chicago area, as a function of land use and curb length.
|Land use||Pounds/Dry Day/100 ft-curb|
|Single Family Residential||0.7|
|Multi Family Residential||2.3|
|Undeveloped or Park||1.5|
The above table implies that dust and dirt buildup is a linear function of time.
Three methods are available to calculate the buildup of dust and dirt on a sub-catchment:
Calculate the dust and dirt buildup using the power linear function to the right of this item. Linear buildup is simply a subset of a power function buildup.
Power Linear Factor (J2 - DDFACT). The multiplication factor in the power-linear form. The unit of this parameter depends on the Buildup Dependency option, as follows:
|Unit of DDFACT in power-linear form|
|Curb Length||lb/(100 ft curb/day^DDPOW) [kg/(km curb)/day^DDPOW]|
DDPOW = Power in the power-linear form
Power (J2 - DDPOW). The power in the power-linear formulation. This parameter has no units. Linear buildup can be simulated by setting this parameter to 1.0.
Calculates the dust and dirt buildup using the exponential function. This form of buildup has an asymptotic trend.
Exponent (J2 - DDPOW)
This parameter is the familiar exponential decay constant in units of 1/day. This type of relation will be evidenced by a semi-log plot of buildup versus time indicating a linear relationship.
Calculate the dust and dirt buildup using the Michaelis Menton function to the right of this item. This form of buildup has an asymptotic trend. Generally, this formulation rises steeply (in fact linearly for small values of time) and then approaches the asymptote slowly.
Michaelis - Menton Factor (J2 - DDFACT). This parameter, in days, is interpreted as the half-time constant, ie. the time at which buildup is half of the maximum (asymptotic) value.
Street sweeping parameters are used to calculate the removal of dust and dirt for a landuse. This Dialog displays the buildup of dust and dirt for a typical landuse during a dry period.
If this button is greyed out it can be reactivated by selecting street sweeping from within the Job Control -> Water Quality dialog.
Percentage of the landuse area within a subcatchment where street sweeping is available. This may relate to the percentage of curb available for sweeping when dealing with parked cars, for example.
Average number of days between cleaning.
Number of days before the start of simulation since street sweeping was performed. This parameter is used to estimate the buildup prior to the start of the simulation.