Updated Watershed tool provides even more detailed catchment characteristics
- New releases
We are constantly inspired by our users and their ideas on how to improve different tools and analyses in SCALGO Live. Today, we are proud to announce that some of the most frequently suggested improvements of the Watershed tool has been released.
We have added a brand new set of catchment characteristics that enable you to gain an even deeper understanding of your watershed. We have thought long and hard about how to present this new information in a way that is fast, interactive and visual – we hope you like it.
The new information can be used for estimating hydrological response time when dimensioning culverts, as input to hydrological modelling, as a starting point when screening for measures to slow down water, and much more. Here’s a short introduction to the interesting new catchment characteristics and cool new visualisations.
Longest path in a catchment
Now SCALGO Live automatically computes the longest flow path in a catchment. Click at any point in the terrain to see the longest flow path to that point, including the flow path length and average slope.
Use this information to estimate the concentration time of the watershed, i.e. the time needed for runoff to travel from the most remote point to the outlet.
![](https://scalgo-web.imgix.net/images/longest-path.jpg?auto=compress%2Cformat&crop=focalpoint&cs=srgb&fit=crop&fp-x=0.5&fp-y=0.5&h=521&q=80&w=750&s=6a76756bf98a4b153f8c83edbc70df6a 750w, https://scalgo-web.imgix.net/images/longest-path.jpg?auto=compress%2Cformat&crop=focalpoint&cs=srgb&fit=crop&fp-x=0.5&fp-y=0.5&h=695&q=80&w=1000&s=2984d409531beb6d40924fb731c90233 1000w, https://scalgo-web.imgix.net/images/longest-path.jpg?auto=compress%2Cformat&crop=focalpoint&cs=srgb&fit=crop&fp-x=0.5&fp-y=0.5&h=869&q=80&w=1250&s=9a05b754aba616b2fc980e807b8a469c 1250w, https://scalgo-web.imgix.net/images/longest-path.jpg?auto=compress%2Cformat&crop=focalpoint&cs=srgb&fit=crop&fp-x=0.5&fp-y=0.5&h=1043&q=80&w=1500&s=c4864ce5a97b55987332deab828f0325 1500w, https://scalgo-web.imgix.net/images/longest-path.jpg?auto=compress%2Cformat&crop=focalpoint&cs=srgb&fit=crop&fp-x=0.5&fp-y=0.5&h=1216&q=80&w=1750&s=44eacd94a8aef83fbdf550ff2a75fbd8 1750w)
Figure 1. The longest flow path is shown as a red line through the watershed. In the watershed info box you see the length and slope of the longest path.
Length/area histogram - characterising the shape of your catchment
To supplement the longest path, we also give you the Length/area histogram with a more in-depth characterisation of all flow paths. This histogram describes how the area of a watershed is distributed across various flow path lengths. Why is this useful? Because all watersheds are unique and have very different shapes (even if they have the same longest flow path length), and this ultimately affects runoff behaviour.
Use the Length/area histogram to answer questions such as:
- How large an area of the watershed is closer than x meters to the outlet?
- How long are other flow paths in the watershed compared to the longest flow path?
As an extra bonus to our Danish users, we’ve also visualized the land cover distribution in each histogram column which allows you to assess e.g. the infiltration effects of impervious areas. This feature will soon be available in other countries too.
![](https://scalgo-web.imgix.net/images/concentration.jpg?auto=compress%2Cformat&crop=focalpoint&cs=srgb&fit=crop&fp-x=0.5&fp-y=0.5&h=545&q=80&w=750&s=447563bed8053a4ac35bde17e96ef609 750w, https://scalgo-web.imgix.net/images/concentration.jpg?auto=compress%2Cformat&crop=focalpoint&cs=srgb&fit=crop&fp-x=0.5&fp-y=0.5&h=636&q=80&w=876&s=58bc34793684052c65f92588fc0d0686 876w)
Figure 2. The Length/area histogram describes the how the area of a watershed is distributed across various flow path lengths. Here, red is buildings, orange is other impervious, and green is pervious.
Note that if you click on one of the bars in the chart you can interactively identify the part of the catchment corresponding to the chosen flow path lengths.
![](https://scalgo-web.imgix.net/images/last-fig.jpg?auto=compress%2Cformat&crop=focalpoint&cs=srgb&fit=crop&fp-x=0.5&fp-y=0.5&h=561&q=80&w=750&s=70581842fb12a1355e545817392b2b64 750w, https://scalgo-web.imgix.net/images/last-fig.jpg?auto=compress%2Cformat&crop=focalpoint&cs=srgb&fit=crop&fp-x=0.5&fp-y=0.5&h=749&q=80&w=1000&s=f5561a97e8491bd4080b234b02e78d63 1000w, https://scalgo-web.imgix.net/images/last-fig.jpg?auto=compress%2Cformat&crop=focalpoint&cs=srgb&fit=crop&fp-x=0.5&fp-y=0.5&h=935&q=80&w=1249&s=b9fdcdd268c6713fcfe564dbd4da05b0 1249w)
Figure 3. The area that has a flow path to the query point with a length less than the upper limit of the selected bar in the histogram is highlighted on the map.
How to read the histograms
Below are a few examples of what different shapes of histograms can tell you about your watershed:
1) Most flow paths in the watershed are much shorter than the longest path. This indicates that a large part of the catchment area drains towards the outlet faster than the concentration time.
2) Many flow paths are similar in length to the longest flow path. This indicates that most of the catchment area is far away from the outlet and runoff from these flow paths will reach the outlet approximately at the same time.
![](https://scalgo-web.imgix.net/images/flow-paths-example2.jpg?auto=compress%2Cformat&crop=focalpoint&cs=srgb&fit=crop&fp-x=0.5&fp-y=0.5&h=259&q=80&w=750&s=1889cc2616ecf29e84cde02ae8caecd6 750w, https://scalgo-web.imgix.net/images/flow-paths-example2.jpg?auto=compress%2Cformat&crop=focalpoint&cs=srgb&fit=crop&fp-x=0.5&fp-y=0.5&h=345&q=80&w=1000&s=49a617df20075328cd18a87d53193498 1000w, https://scalgo-web.imgix.net/images/flow-paths-example2.jpg?auto=compress%2Cformat&crop=focalpoint&cs=srgb&fit=crop&fp-x=0.5&fp-y=0.5&h=431&q=80&w=1250&s=ac15ecd6dee570fd2ac9f27b3545e7cd 1250w, https://scalgo-web.imgix.net/images/flow-paths-example2.jpg?auto=compress%2Cformat&crop=focalpoint&cs=srgb&fit=crop&fp-x=0.5&fp-y=0.5&h=518&q=80&w=1500&s=9b5aa5592f56feb82f4cd97bfe518f9b 1500w, https://scalgo-web.imgix.net/images/flow-paths-example2.jpg?auto=compress%2Cformat&crop=focalpoint&cs=srgb&fit=crop&fp-x=0.5&fp-y=0.5&h=604&q=80&w=1750&s=a8e51febc4bd24ef9792747580e11543 1750w)
Figure 4. 1) Most flow paths are much shorter than the longest flow path 2) There are many flow paths in the catchment that are similar in length to the longest flow path.
What do you think?
Try the new expanded watershed tool and let us know what you think! If you have any questions don’t hesitate to contact us at info@scalgo.com.
![](https://scalgo-web.imgix.net/images/Helena.jpg?auto=compress%2Cformat&crop=focalpoint&cs=srgb&fit=crop&fp-x=0.5&fp-y=0.5&h=120&q=80&w=120&s=352a182cccf0a2d6733ed72243e87d4f 120w, https://scalgo-web.imgix.net/images/Helena.jpg?auto=compress%2Cformat&crop=focalpoint&cs=srgb&fit=crop&fp-x=0.5&fp-y=0.5&h=180&q=80&w=180&s=8d2cf103066e04346c7edd487664def1 180w, https://scalgo-web.imgix.net/images/Helena.jpg?auto=compress%2Cformat&crop=focalpoint&cs=srgb&fit=crop&fp-x=0.5&fp-y=0.5&h=240&q=80&w=240&s=70b0ffaeaf4ae362e023c4fd9cbc0cfe 240w, https://scalgo-web.imgix.net/images/Helena.jpg?auto=compress%2Cformat&crop=focalpoint&cs=srgb&fit=crop&fp-x=0.5&fp-y=0.5&h=360&q=80&w=360&s=b27b8f6a71b7e7a7d39ff117291eaf70 360w)