---
title: "Urban settings - Dynamic Wave tab | Technical Reference"
slug: "urban-settings-dynamic-wave-tab"
description: "Learn about the dynamic wave tab in the model settings window. Find the calculation specifications and the option to select a force main equation. "
tags: ["1D urban modelling"]
updated: 2026-10-16T18:26:12Z
published: 2026-10-16T18:26:12Z
canonical: "help.floodmodeller.com/urban-settings-dynamic-wave-tab"
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.

# Urban settings - Dynamic Wave tab

![](https://cdn.document360.io/5074bc26-a9ef-4bf4-b1de-a5c6ce628aca/Images/Documentation/dynamicwavetab.png?sv=2026-02-06&spr=https&st=2026-10-31T04%3A26%3A26Z&se=2026-10-31T05%3A26%3A26Z&sr=c&sp=r&sig=pWkUqLBalzU9AgiVDHYdZFnXGSenm9OWLABGBUHJJEg%3D)

The **Calculation Specifications** are specified here; a user can select a **Force Main Equation** from either the Hazen-Williams or Darcy-Weisbach formulae to compute friction losses for pressurised flow.

The **Variable Timesteps** checkbox will be checked by default. This needs to be unchecked if integrating your urban network with river networks and/or 2D components.

We refer the user to the [EPA Manual](https://www.epa.gov/sites/default/files/2019-02/documents/epaswmm5_1_manual_master_8-2-15.pdf) for further details on this tab of the urban Model Settings window.