---
title: "Steady flows| Technical Reference"
slug: "steady-flows-overview"
description: "Find the theory behind steady flow for 1D modelling."
tags: ["1D river modelling", "1D urban modelling"]
updated: 2022-08-07T16:25:16Z
published: 2022-08-07T16:25:16Z
canonical: "help.floodmodeller.com/steady-flows-overview"
stale: true
---

> ## Documentation Index
> Fetch the complete documentation index at: https://help.floodmodeller.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Steady flows

To start an unsteady flow run, an estimate of the *initial conditions* (flow and stage) is required at every model node. This is most often obtained by carrying out a steady state run at the proposed start time. However, steady state simulations may also be a valid modelling technique under certain conditions.

Two methods are available within Flood Modeller to compute steady flows. The [Pseudo-Timestepping Method](/v1/docs/pseudo-timestepping-method) uses the Preissmann 4-point scheme, whereas the [Direct Method](/v1/docs/direct-method) uses a quite different and highly accurate solution technique.

Topographic data, including channel cross-sections and structure dimensions for example, are assembled into a datafile. This datafile represents the channel network system which may be very complex; it may be looped or branched and contain many interacting flow paths. The datafile will also contain the appropriate boundary conditions at the upstream and downstream extents of the model.