🌾 Engineered Swales (Manning n = 0.20-0.25, Minimum 9-Minute Hydraulic Residence Time)

Vegetated Bioswale Hydraulic Calculator

Size engineered grass and vegetated bioswales treating highway and roadside stormwater runoff: calculate high grass retardance Manning’s roughness coefficient (n = 0.20 to 0.25), verify maximum water depth (<4 inches for water quality storm), ensure minimum 9-minute hydraulic residence time for bio-filtration, and civil landscaping yields.

1. Project & Operating Inputs

Bioswale Channel Length (Linear Feet e.g. 600 Linear Feet Channel)

Channel Longitudinal Slope (% e.g. 1.5% Mild Hydraulic Slope)

Customer Bid Price for Excavated, Topsoiled & Hydroseeded Swale ($ / Lin Ft)

Trapezoidal Trenching, Erosion Control Matting, Deep-Rooted Turf ($ / Ft)

2. Financial Breakdown & Yield

BIORETENTION BIOSWALES

Turnkey Roadside Bioswale Project Profit

Civil Stormwater Infrastructure Margin

0.0%

Gross Revenue / Bill

Total Project CapEx

Operating / Direct Cost