See which reaches moved before the crew goes out.
A before/after pair of the reach after a high-flow event: channel outline, new bars and the sediment plume, from high-res multispectral satellite imagery.
- GSD
- 0.5–2 m
- Cadence
- Event driven
- Platform
- High-res satellite
- Spectral
- Multispectral
t0 Before the event
t1 After the water drops
The week after the water drops
The river peaks overnight and falls over the next few days. By Monday the phone has started. An operations supervisor says a bank has gone below a bridge. A landowner says the channel has cut across a field. Someone at the harbour reports brown water well out past the mouth. You are the geomorphologist, and the question put to you is where the field crew goes first.
You have a channel centreline from the last resurvey and not much else. The crew can walk or boat only so much of the reach, and the visits are queued behind inspections of culverts and defences. So the first reaches checked are the ones that rang in, which is not the same as the ones that moved. A quiet stretch with a new point bar and a narrowing channel can go unvisited until the next survey round, and by then the next event has reworked it.
River Morphology puts a matched before and after image of the reach in front of you once the water is down and the sky is clear: the channel outline in each, the bars that formed, and how far the plume spread into the receiving water. It does not replace the resurvey. It tells you where to spend it.
What you get
One event, one pair
2.1
Before/after channel outline
GeoPackage or shapefile
Vector outlines of the channel in the before and after images, so you can lay one over the other in QGIS or ArcGIS and see where the bank line moved. Where the channel has shifted sideways or taken a new course, it shows as the gap between the two lines.a, f
2.2
Bar and bank change summary
PDF
A short note listing the reaches where bars formed or grew and where banks look to have retreated, with the image dates behind each. Written to sit in a post-event note or a resurvey brief.d
2.3
Sediment plume extent
GeoPackage or shapefile
The outline of the visible plume where the river meets the receiving water, for the after image. Where the plume cannot be told from the water around it, the summary says so.e
2.4
Image pair
GeoTIFF or PNG
The before and after scenes cropped to the reach, with their acquisition dates, for the file and for showing a manager what moved.
Each pair is made on request after an event. Nothing runs by itself between events.
How it works
3.1
Send the reach
Give us the reach or the authority boundary, as a shapefile or GeoPackage, and say roughly when the event happened.b
3.2
Pick the images
We choose a before image from ahead of the event and the first usable clear image after the water has fallen, both multispectral and matched as closely as the archive allows.c
3.3
Compare
Channel outline, bars and plume are traced in each image and set against each other.
3.4
Hand-over
You get the outline layers, the image pair and the change summary. Open them in your GIS and use them to rank the reaches.
Limits
- Planform only
- Optical imagery shows the shape of the channel from above. It does not show depth, and it cannot give the volume of sediment moved. Anything that needs a cross-section or a bed level needs a survey.
- You ask for the pass
- There is no event detection and no continuous watching. A pair is made when you tell us an event warrants one.
- Cloud sets the date
- The after image waits for the first usable clear view. A cloudy aftermath delays delivery, and the summary gives the date the image was taken, which may be well after the peak.
- 0.5–2 m is the floor
- A bar or a bank retreat of a pixel or two will not show. Narrow channels may be only a few pixels wide, and small headwater streams are beyond what this resolves.
- Water clarity and sun angle
- How far the plume shows depends on how clear the receiving water is and where the sun sits at capture. A plume that looks pale to a boat crew can be invisible from orbit.
- Vegetation and shadow
- Tree cover can hide a bank line, and a steep bank can throw a shadow across it. Those stretches are marked as not resolved in the summary.
Who it's for
Who it's for
- Fluvial geomorphologists and river engineers at a river authority who have to decide which reaches get a resurvey after a high-flow event.
- Teams who want a first look at the reach before a crew is committed.
- Flood and coastal risk managers who need to know whether a plume or a moved bank points at an asset.
Who it's not for
- Teams that need depth, bed level or sediment volume. That takes a bathymetric or topographic survey.
- Live flood response. A pair arrives after the water has fallen, not during the event.
- Continuous or real-time river monitoring.
- Single-bank surveys at centimetre scale. A drone or a total station does that better.
FAQ
Questions from river teams
Does this replace a topographic resurvey?
No. It flags where change happened so the resurvey goes to the right reaches first. The survey still gives you the levels.
What if the event is followed by cloud?
The after image waits for the next usable clear view. That can delay delivery, and the summary gives the date the image was taken.
Can it measure depth or the volume of sediment moved?
No. Optical imagery shows the planform of the channel and nothing about the bed.
How is a pass triggered?
You tell us when an event warrants a look. Nothing watches the river for you.
Does the plume always show clearly?
Not always. It depends on water clarity and sun angle at capture, and where it is faint the summary says so.
How do we check it against our own survey?
Every outline carries the date of the image it came from, so you can lay it over a resurvey, a walkover or the photos your staff took on site. Tell us where your ground truth is when the reach is scoped.
Will it fit our channel centreline and reach divisions?
Send them with the reach and the change summary can be broken out by your divisions.
Who owns the layers?
Use and ownership terms for the delivered layers are written into the contract before the pilot starts. The satellite archives the images come from keep their own licences.
How is a pilot priced?
A pilot is scoped on the reach, the number of events and the period you want covered, and you get a written scope to take through procurement.
Send us your next event reach.
Tell us the reach and the event, or ask in the chat.