Flood Design Workflow

One place to launch your flood‑related tools – from catchment response and runoff to routing, culverts, channels, scour, roadway hazard, and stage–storage curves.

Toolchain Overview Hydrology & Hydraulics

Follow the steps in order for a typical design flow, or jump straight to the tool you need. Adjust the links below to match your actual filenames / paths on ToolsForEngineers.com.
Step 1 Catchment response – Tc & lag

Estimate time of concentration (Tc) and watershed lag, then pick a compatible design storm duration.

  • Tc (min / hr) from NRCS, Kirpich or travel‑time.
  • Lag for NRCS hydrograph methods.
Open Tc tool
Step 2 Rainfall & runoff – peak flows

Use your rainfall / runoff tools to turn design storms into peak flows and inflow hydrographs.

  • Rational method peak discharge.
  • SCS CN / unit hydrograph inflow curves.
Rainfall / IDF tool Runoff / hydrograph tool
Step 3 Detention / reservoir routing

Route inflow hydrographs through storage to get attenuated outflows for each scenario.

  • Peak outflow after attenuation.
  • Outflow hydrograph for downstream checks.
Reservoir / routing tool
Step 4 Outlet & culvert sizing

Size outlet works (weirs, orifices, culverts) to safely pass the routed flows.

  • Culvert / outlet dimensions and type.
  • Headwater / tailwater checks.
Culvert / outlet tool
Step 5 Channel capacity & freeboard

Check that key channels / rivers can convey design flows with acceptable freeboard.

  • Depth and velocity from Manning’s equation.
  • Freeboard to levees, roads, and structures.
Channel capacity tool
Step 6 Scour & anti‑scour checks

Estimate general scour depth and check armour / bed stability near the structure.

  • Lacey / USBR general scour depths.
  • Izbash / Shields velocity thresholds.
Scour / anti‑scour tool
Step 7 Roadway / low‑water crossing hazard

Screen hydraulic hazard at roads using depth, velocity and depth–velocity product.

  • Depth, velocity and d·V indicators.
  • Qualitative hazard rating for users.
Roadway hazard tool
Step 8 Stage–storage / stage–area curves

Build stage–storage or stage–area curves for reservoirs and floodplain cells.

  • Stage–area input from surveys, GIS or model output.
  • Mid‑area based stage–storage rating table.
Stage–storage builder

This sequence is a generic workflow for many small‑to‑medium flood projects. Real projects may add extra steps (e.g. 2D floodplain modelling, bridge scour, climate‑change allowances, dam‑safety checks).