Showing posts from January, 2019

How to Use Population for DWF in SWMM5 and InfoSWMM

The SWMM5 engine uses mean flow as the dry weather flow value (DWF) and not population but does allow weekday, weekend, daily and monthly patterns.  You can use these many pattern options to actually use population in the SWMM5 and InfoSWMM dry weather flow tables.  Here are the steps as shown in the embedded image: Population in the Value field,Per Capita flow in the Monthly Pattern field,Weekday patternWeekend patternConversion (if needed) from the per capita units to the current units of SWMM5 or InfoSWMMThis can make SWMM5 and InfoSWMM more like Innovyze products XPSWMM, InfoWorks ICM and InfoSewer.

Runoff Coefficient and Time of Concentration for InfoSewer

Runoff Coefficient and Time of Concentration for InfoSewerRunoff coefficient is loosely defined as the ratio of runoff to rainfall, and is a function of watershed characteristics including land use, soil type, and slope of the watershed. The value of runoff coefficient ranges between 0.0 and 1.0. A value of 0.0 means that all of the rainfall is lost in the form of abstractions such as infiltration, interception, and evaporation and none of the rainfall is converted to runoff. The value of 1.0 implies that all the rainfall is converted to runoff and is discharged from the watershed. As an example, most of the rain that falls on impervious areas such as pavement and roof would be immediately converted to runoff. A value of C for such land uses is close to 1.0. Runoff coefficient values recommended by the American Society of Civil Engineers and Water Environment Federation for return periods not exceeding 10 years are given below for various land uses, soil types, and slope condi…