---
title: "How to join two river reaches | Tutorials"
slug: "how-to-join-two-river-reaches"
description: "Watch the video on how to join tributaries within Flood Modeller."
tags: ["1D river modelling"]
updated: 2023-03-07T13:16:17Z
published: 2023-03-07T13:16:18Z
canonical: "help.floodmodeller.com/how-to-join-two-river-reaches"
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.

# How to join two river reaches

Modelling tributaries is one way to account for additional water entering a main river reach.

Effectively representing all flows and water levels within a river is key to better accuracy.

[Embedded content](https://www.youtube.com/embed/iZ4N8uTv3ys?&wmode=opaque&rel=0)

### Example dataset

Download the sample dataset used within the video:

[Tributary.zip](https://floodmodeller-knowledgebase.s3.eu-west-2.amazonaws.com/Tributary.zip)

### Steps

1. In the **1D River Network** table, select the River Section in your main river reach located where the tributary will join. Right-click and select **Copy**.
2. In the **1D River Network** table, select the node at the most downstream end of the tributary. Right-click and select **Paste**. Label this new node (for example TribDS).
3. Repeat step 1 above.
4. In the **1D River Network** table, select the node in the main reach immediately upstream of where the tributary will join. Right-click and select **Paste**. Label this new node (for example MainDS).
5. In both of the new nodes TribDS and MainDS, set the **Distance to Next** = 0.
6. In the **1D River Build** tab, click on the **Junction** dropdown and select **Open Junction**. Click on the **Map** view to add this where the reaches join.
7. Provide the node labels of both new nodes TribDS and MainDS, and the River Section where the tributary joins, as labels 1, 2 and 3. These can be provided in any order.
8. To the pop-up asking if you would like to connect to these nodes, click **Yes**.
9. Your tributary is now joined to your main river reach. Make sure you save the adjusted river network!