DitchSoft© is a ditch and open channel analysis program developed to evaluate the performance of natural channels (irregular shape with varying Manning's n values) and constructed channels (rectangular, triangular or trapezoidal shapes). DitchSoftVA© is designed for use in the Commonwealth of Virginia and by the Virginia Department of Transportation [VDOT]. The program uses the design methodology for minor channels in accordance with VDOT’s Drainage Manual.
Each channel can be divided into many sections depending on the change of shape or grade and analyzed. Appropriate VDOT St’d. lining is recommended for each section.
Adequate receiving channel analysis can also be performed as required by Minimum Standard 19 Criteria of the Virginia Erosion & Sediment Control Handbook:
1. The natural channel runoff from a 2-year storm shall not overtop its banks nor erode after development of the site.
2. The runoff in a constructed channel for a 10-year storm shall not overtop its banks, while bed or bank erosion shall not occur due to a 2-year storm.
Hydraulic analysis of open channels is done using the single section method, an application of Manning’s equation to analyze uniform or nearly uniform flow conditions. The flow velocity is compared with the maximum permissible velocity (MPV) for the channel bed and bank soils and the lining material.
DitchSoft© also provides the tractive force (permissible shear) method for ditch lining design. Unvegetated channels and four lining types – Vegetative lining, Manufactured (RECP) lining, Rock Riprap and Concrete – can be analyzed. Permissible soil / lining shear are calculated using procedures described in FHWA’s HEC-15, Design of Roadside Channels with Flexible Linings. Soil classification is based on ASTM.
Corrections may be applied based on flow depth and channel curvature.
