Edit Snow Packs

Create or edit Snow Pack objects.

Snow Pack objects contain parameters that characterise the buildup, removal, and melting of snow over three types of sub-areas within a subcatchment:

• The Plowable snow pack area consists of a user-defined fraction of the total impervious area. It is meant to represent areas such as streets and parking lots, where plowing and snow removal can be done.

• The Impervious snow pack area covers the remaining impervious area of a subcatchment.

• The Pervious snow pack area encompasses the entire pervious area of a subcatchment.

Each of these three areas is characterized by the following parameters:

• Minimum and maximum snow melt coefficients.

• Minimum air temperature for snow melt to occur.

• Snow depth above which 100% areal coverage occurs.

• Initial snow depth.

• Initial and maximum free water content in the pack.

In addition, a set of snow removal parameters can be assigned to the Plowable area. These parameters consist of the depth at which snow removal begins, and the fractions of snow moved onto various other areas.

Subcatchments are assigned a snow pack object through their Snow Pack property. A single snow pack object can be applied to any number of subcatchments. Assigning a snow pack to a subcatchment simply establishes the melt parameters and initial snow conditions for that subcatchment. Internally, SWMM creates a "physical" snow pack for each subcatchment. This snow pack tracks snow accumulation and melting for that particular subcatchment based on its snow pack parameters, its amount of pervious and impervious area, and the precipitation history it sees.

Procedure

1. The Snow Pack Editor displays.

There are two pages:

• Parameters - Specify parameters that characterize the buildup, removal, and melting of snow over three types of sub-areas within a subcatchment.

• Removal Parameters - Specify snow removal parameters for the plowable area.

2. Create a new snow pack set or edit an existing set.

3. Click OK to save your changes.