Civil Drainage & Highways Calculators
Culvert and storm drain capacity, detention storage, asphalt quantities and horizontal curve geometry for site drainage and highways.
Culvert Capacity Calculator
Full-flow culvert capacity and velocity from the Manning equation, or the smallest barrel that passes a design flow.
Q = (1/n) A R^(2/3) S^(1/2) with R = D/4 for a full circular barrel Culvert Scour Calculator
Local scour hole depth at a culvert inlet from the HEC-18 inlet shear relation, with the live-bed alternative reported separately rather than added to it.
u* = C_d·v·√g; τ_c = θ_c·ρ_w·(s−1)·g·D50; y_s = 0.325·(y_t·D50/τ_c) Storm Drain Sizing Calculator
Select the smallest standard storm drain pipe that passes the design flow and check the self-cleansing velocity.
Q = (1/n) A R^(2/3) S^(1/2) with a minimum velocity check of about 0.75 m/s Detention Basin Calculator
Detention storage volume and pond footprint from the peak inflow, the permitted discharge and the design storm.
Q = 2.78 C i A ; V = (Qin - Qout) t Asphalt Quantity Calculator
Convert plan area and layer thickness into asphalt volume, tonnage and the number of tipper deliveries needed.
V = A x t ; m = V x density x (1 + waste) Pavement Layer Calculator
Required flexible pavement thickness from wheel load and section modulus, split into wearing course, base and sub-base by the equivalency factors you supply.
ε_z = 1.5·q_v/E_p · 1/√(1+(h/a)²); h = a·√(k²−1) Horizontal Curve Calculator
Circular curve geometry from the deflection angle and radius, with a speed check from superelevation and side friction.
T = R tan(d/2) ; E = R(sec(d/2) - 1) ; M = R(1 - cos(d/2)) ; V = sqrt(gR(e+f))