Single Cross‑Section Water Level Tool (HEC‑RAS‑like)

Manual — how to use

On page load, a sample cross section + sample discharges are loaded and solved automatically (so you see plots immediately).
Paste geometry: click Paste geometry (popup) or paste directly into the first Station cell — paste two Excel columns (Station, Elevation). Rows are created automatically.
Paste many Q values: in “Discharges”, paste one Excel column.
Select method:
- Normal depth: solve Q = K·√S0 (needs slope S0)
- Critical depth: solve (Q²·T)/(g·A³)=1
- Known stage: use your stage directly and compute hydraulics for each Q
Results update automatically as you edit (auto‑solve runs after a short pause). Use Reset sample to restore the example. Use Clear all to start from scratch. Use Download results CSV to export.

To match HEC‑RAS closely, use the same station–elevation points, the same bank stations (LOB/CH/ROB) and Manning’s n values, and the same slope for normal depth.

Inputs

UI zoom

Computation method

Method Slope S0 (m/m) (required for normal depth)

Known stage (W.S. elev,m) (used only for “Known stage”) Gravity g m/s²)

Flow regime Units

Flow regime controls how the tool interprets normal vs. critical conditions (similar to HEC‑RAS).

Roughness

Left bank station x Right bank station x

n LOB n CH n ROB

Optional composite roughness: if both bank stations (LB/RB) are inside the station range, the tool splits into LOB / CH / ROB (like HEC‑RAS). If LB/RB are blank or outside, the tool uses a single n CH only. Bank stations are marked on the ground line in the plot.

Discharges (paste many at once)

Paste from Excel: click the first cell under “Q” and press Ctrl+V (single‑column paste is supported).

#	Q (m³/s)

Cross‑section points (Station–Elevation)

Paste two Excel columns into the table: Station (x) and Elevation (z). Rows are created automatically when you paste.

#	Station (x, m)	Elevation (z, m)

Max search above thalweg (m) Stage tolerance (m)

Geometry CSV import (optional)

Download template Import CSV

CSV columns: x,z (or Station,Elevation). Extra columns ignored.

Loading sample…

Rating curve

Cross‑section viewer

W.S. — m

Discharge

W.S.

—

Depth@thalweg

—

Blue = water (HEC‑RAS style). Dotted blue lines show where the water surface meets the ground (wetted edges). Bank stations (used for composite roughness) are marked on the ground line.

Results

Q	W.S.	EGL	Depth@Thalweg	Area	Top width	V	Fr	K	α	Sf	h_minor