Parameters
Contents
Geographic Location
•State:
States with available T25 values are listed in the drop down box.
•County / City:
Counties / parishes / cities located within the selected state that have available T25 values.
Physical Parameters
•Ditch Depth / Depth to Water in Pit:
Depth from soil surface to normal water level in ditch or in borrow pit.
•Surface Depressional Storage:
Related to microtopography. Indicates the average value of depressional storage before runoff can begin. This value may be low for a well graded landscape of high for a wooded area.
•Depth to Restrictive Layer:
Depth from soil surface to the aquitard or aquiclude or to an impervious or very low conductivity soil layer.
•Drainable Porosity:
Drainable porosity is defined as the volume of water drained for a given change in water table depth. These values can be determined by soil water characteristic curves. If the user has soil files developed for use in the DRAINMOD model, the drainable porosity value used in the Lateral Effect model can be determined by dividing the volume drained at a depth of 30 cm by the value 30. If no data are available it is suggested to use values of 0.035 to 0.04.
T25 Override
•Override Default T25 Value:
This option allows the user to enter in their own T25 value in lieu of pre-calculated values. T25 values are determined using a very specific methodology. Please consult the model authors if T25 for locations other than those listed in the model are required for your project. Incorrect development of T25 values will result in a poor determination of the lateral impact.
•User Specified T25:
Enter your T25 values in days. Can be decimal number.
Hydroperiod
•Select the continuous saturation period. For example, a hydroperiod of 5% indicates that the water table is within 12 inches (30 cm) of the soil surface for a continuous period of 5% of the growing season (as defined by that locations NRCS WETs table for 28°F and 50% probability).
Location Notes
•These notes will indicate if a specific criteria, i.e. 1/2 inch surface storage, is available for the location chosen.
See also: