Approach Canal (Gravel Trap → Settling Basin) — Rectangular Canal Calculator

Replicates your Excel logic (including the same exponent 0.667) and prints values to 3 decimals for easy comparison. Includes checks, tables with Excel cell refs, and built-in diagrams/charts.

Units

Inputs (with Excel cell references)

Sample values come from your workbook Approach canal to settling basin.xlsx, sheet App. Canal Gravel to Settling, mainly cells E17–E34 and checks E47–E48.
Canal section
Excel: E16
Manning roughness, n
Excel: E17
Design discharge, Q40
Excel: E19
m³/s
Flushing factor (adds Q40*(1+f))
Excel: E20
No. of canals, N
Excel: E26
nos.
Max velocity limit, Vmax
Excel: E18 / E29
m/s
Water level at canal start (U/S), WL₀
Excel: E21
m
Water depth, d
Excel: E23 / E41
m
Canal width, b
Excel: E24
m
Freeboard, FB
Excel: E34
m
Canal length, L
Excel: E33
m
Min particle size to be settled in gravel trap, dₘᵢₙ
Excel: E48
mm
Auto-updates as you type. Displays are rounded to 3 decimals; internal math uses full precision.
Input visualization — Canal cross-section (SVG)
Diagram is to-scale-ish for readability (not a construction drawing).
Quick charts (helpful during design review)
Velocity & Froude vs depth (holding Q and b)
Required bed slope S vs depth (Manning, holding Q, b, n)
Longitudinal profile (uniform-flow assumption): invert & water surface along length

Results (3 decimals + Excel-cell mapping)

Discharge per canal, Q (Excel: E27)
m³/s
Velocity, V (Excel: E28)
m/s
Bed slope, S (Excel: E31)
(m/m)
Slope form (Excel: E32)
Start invert level, Zinv₀ (Excel: E22)
m
Total depth, D = d + FB (Excel: E42)
m
Critical velocity, Vc (Excel: E43)
m/s
Froude number, Fr (derived)
S.N. Item Excel cell Symbol Value Unit Remarks / checks
“Excel match mode”: slope uses R^0.667 (not exactly 2/3) to replicate your sheet.
Formulas used (same as your Excel logic)
Q = Q40 * (1 + f) / N A = b * d P = b + 2d R = A / P V = Q / A S = ( (n * V) / (R^0.667) )^2 ← matches Excel Slope ratio = round(1/S, 0) → “1 : x” D = round(d + FB, 1) Vc = sqrt( g * (A / b) ) = sqrt(g * d) (rectangular channel) Fr = V / sqrt(g * d) Sediment (simplified Shields/tractive): d(mm) = 11 * R * S * 1000
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