Land Uses

• Pollutant buildup

• Pollutant washoff

• Street cleaning

• Power Function: Pollutant buildup (B) accumulates proportionally to time (t) raised to some power, until a maximum limit is achieved,

$B = M \ln(C_1 C_2 t^{C_3})$ Here $C_1$ = maximum buildup possible (mass per unit of area or curb length), $C_2$ = buildup rate constant, and $C_3$ = time exponent

• Exponential Function: Buildup follows an exponential growth curve that approaches a maximum limit asymptotically, 

$B = C_1 \left(1 - e^{-C_2 t}\right)$ Here $C_1$ = maximum buildup possible (mass per unit of area or curb length) and $C_2$ = buildup rate constant (1/days).

• Saturation Function: Buildup begins at a linear rate that continuously declines with time until a saturation value is reached,

$B = \frac{C_1 t}{C_2 + t}$ Here $C_1$ = maximum buildup possible (mass per unit area or curb length) and $C_2$ = half-saturation constant (days to reach half of the maximum buildup).

• External Time Series: This option allows one to use a Time Series to describe the rate of buildup per day as a function of time. The values placed in the time series would have units of mass per unit area (or curb length) per day. One can also provide a maximum possible buildup (mass per unit area or curb length) with this option and a scaling factor that multiplies the time series values.

• Exponential Washoff: The washoff load (W) in units of mass per hour is proportional to the product of runoff raised to some power and to the amount of buildup remaining,

$W = C_1 Q^{C_2} B$ Here $C_1$= washoff coefficient, $C_2$ = washoff exponent, q= runoff rate per unit area (inches/hour or mm/hour), and $B$ = pollutant buildup in mass units. The buildup here is the total mass (not per area or curb length) and both buildup and washoff mass units are the same as used to express the pollutant's concentration (milligrams, micrograms, or counts).

• Rating Curve Washoff: The rate of washoff W in mass per second is proportional to the runoff rate raised to some power, 

$W = C_1 Q^{C_2}$ Here $C_1$ = washoff coefficient, $C_2$ = washoff exponent, and $Q$ = runoff rate in user-defined flow units.

• Event Mean Concentration: This is a special case of Rating Curve Wash-off where the exponent is 1.0 and the coefficient C 1 represents the washoff pollutant concentration in mass per liter (Note: the conversion between user-defined flow units used for runoff and liters is handled internally by GeoSWMM).

• Days between sweeping

• Days since the last sweeping at the start of the simulation 

• The fraction of buildup of all pollutants that is available for removal by sweeping 

• The fraction of available buildup for each pollutant removed by sweeping