---
title: "Bridges"
slug: "how-to-add-a-bridge"
description: "Learn how to add a bridge to your 1D river network."
tags: ["1D river modelling", "bridge", "building models"]
status: "new"
updated: 2023-07-10T15:07:15Z
published: 2023-07-10T15:07:15Z
canonical: "help.floodmodeller.com/how-to-add-a-bridge"
---

> ## 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.

# Bridges

Water levels are often influenced significantly by bridges within the watercourse. The normal river equations (Saint-Venant equations) are not always appropriate for application to these structures. Explicit modelling of bridges within the watercourses is therefore required in most cases.

Flood Modeller provides three bridge units to select from:

- [Arch Bridge](/v1/docs/how-to-add-arch-bridges)
- [USBPR Bridge](/v1/docs/us-bpr-bridge)
- [Pier-loss Bridge](/v1/docs/pier-loss-bridge)

It is also possible to [add a Spill unit](/v1/docs/how-to-add-spills-to-bridges) to allow flow to bypass the structure via the deck of the bridge or culvert and return to the channel downstream.