Detailed Overview of landuse_getWashoffQual Function in SWMM5 🌧️🔬📊

 

Detailed Overview of landuse_getWashoffQual Function in SWMM5 🌧️🔬📊

The landuse_getWashoffQual function in SWMM5 calculates the pollutant concentration in washoff from a specific land use. This function is a key component in modeling how pollutants are transported from urban surfaces during rainfall events. Here's an in-depth analysis of its workings:

Function Prototype 📝

• Input:
  • i: Land use index.
  • p: Pollutant index.
  • buildup: Current buildup of the pollutant on the land use (measured in pounds or kilograms).
  • runoff: Current runoff rate on the subcatchment (feet per second).
  • area: Area of the land use (square feet).
• Output: Returns the concentration of the pollutant in the washoff (mass per cubic feet).
• Purpose: To determine the concentration of a pollutant that is washed off from a specific land use during a runoff event.

Calculation Process 🌊🧮

1. Initial Checks:

   • Returns 0.0 if there is no washoff function or no runoff.
   • Returns 0.0 if there's a buildup function but no current buildup.

2. Washoff Function Types:

   • Exponential Washoff (EXPON_WASHOFF):
     • The washoff concentration is calculated using an exponential function of runoff (converted to inches per hour or mm per hour) and the buildup, which is converted to concentration mass units.
     • The calculated concentration is then normalized by runoff and area.
   • Rating Curve Washoff (RATING_WASHOFF):
     • The washoff concentration is determined using a power function of the runoff volume (runoff rate multiplied by area) and an exponent.
   • Event Mean Concentration Washoff (EMC_WASHOFF):
     • The concentration is directly given by the coefficient, which already includes a conversion factor to mass per cubic feet.

3. Coefficients and Exponents:

   • coeff: Represents the coefficient in the washoff equation.
   • expon: The exponent used in the washoff calculations.
   • These values are specific to each pollutant and land use type.

4. Return Value:

   • The function returns the calculated pollutant concentration in the washoff.

Role in Urban Hydrology Modeling 🏙️🔍💧

• This function is crucial for understanding the dynamics of pollutant transport from urban surfaces during storm events.
• It aids in the assessment of water quality impacts from different land uses and helps in designing strategies for pollution mitigation in urban runoff.

Implications for Stormwater Management 🌧️🌳🚧

• The landuse_getWashoffQual function is vital for predicting the environmental impact of urban development on water bodies.
• It supports the effective planning and implementation of green infrastructure and other best management practices for stormwater quality control.

In summary, the landuse_getWashoffQual function in SWMM5 plays a pivotal role in simulating pollutant washoff processes, providing valuable insights for urban water quality management and environmental protection. 🌧️🔬📊🌊🏙️🌳🚧🔍💧🌍📈🌆🌦️🌐🔬💻🌎🚰