Finding needles in haystacks using satellites

Soil and nutrients washing off agricultural land is the single most common reason for our rivers and streams not being as healthy as they should be. Across England it accounts for a quarter of the reasons for waterbodies not achieving good status under Water Framework Directive classifications. In Herefordshire where soils are very light and agricultural practices intensive the figure is a worrying 48%.


Tackling the problem obviously involves finding out where the polluting runoff is coming from. This sounds simple but isn’t! River and stream catchments (the area of land that drains into them) are large. Often the runoff originates quite a distance from the polluted river or stream, finding its way by gravity via roads, paths, ditches and other fields. Also agriculture is a highly mobile industry. 


What is a bare arable field one year might be pasture the next, so the locations of high risk move around.

To help us find the needles in the haystack we’ve turned to modern technology. And it’s working.

Fields of bare soil with no growing crops or grass covering them are clearly much more likely to lose their soil. We can now identify where they are by using the excellent images from the Sentinel 2 satellite which was launched in 2015. 


It crosses the UK every few days so gives us an almost real time picture of land use, although we do have to have clear skies!


We can then overlay other useful information over the top of the satellite imagery which further narrows our search.

Environment Agency LIDAR data provides incredibly accurate information on the height and levels of land. For our search we identify all land that has a slope of more than 6%. This is because soil runoff is much more likely to happen when there is a steep slope.


The next step is to overlay a highly detailed map of the river network. This includes tiny ditches and streams as well as larger rivers and gives a good idea of how soil and nutrients running off the land might find their way into the main river network.


Finally we put on details of soil types. Light, sandy soils are much more likely to be washed off than heavy clays.

By doing all this we can massively reduce the area of the catchment we target for visits by our Environment Officers. 

Our first trial over a whole catchment was carried out on the River Lugg in Herefordshire. Its catchment has a total area of 170 square kilometres. Where to start?!


By selecting areas of bare soil from satellite data we reduced 170km to 30. A lot better but still a massive area to walk over!

By overlaying data layers of steep slopes and soil types we got down to 6.5km and 50 discrete fields. That’s less than 4% of the total catchment area. Much more like it!

Following some typical winter rainfall in early February we mounted an operation to send officers to visit each of the identified 50 locations. They were equipped with iPads (other tablets are available!) with pre-loaded maps and a specially designed app to upload details of what they found. This can include text, photos and video footage. A network connection allows details to be uploaded in real time, although if there’s no reception (fairly common in Herefordshire) data is stored and uploaded as soon as a connection is found.

 
Data and images can been collated immediately and activity coordinated by the operation manager back at the office and also viewed, in real time, by other teams of officers at different locations.


Initial results have been very encouraging. Of the 50 locations visited, 13 were assessed as presenting a high risk of causing immediate pollution problems. 5 were actually causing pollution at the time of the visit despite only relatively small amounts of rainfall.


During the period of the operation no high risk fields were found that hadn’t been highlighted by our targeting system.

We will be contacting all the owners of the 13 high risk locations soon.

Perhaps the most encouraging aspect of the technology (in addition to its accuracy) has been the reaction of our staff who are using it, several remarking it’s revolutionising the way they’re working and making their job far more productive and rewarding.

This is just the start of our journey in using data and technology together in the field to more accurately target our agriculture inspection and regulatory work. It should bring benefits both to the environment and the industry.

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2 thoughts on “Finding needles in haystacks using satellites

  1. Dear Dave,
    Is it possible to use one of your photos in a presentation? It was the aerial photo posted on February 12, 2015. We did some research work on the impacts of flooding on soil quality in the area and it would be really useful to show the extent of the flooding.
    Many thanks
    Davey

    Environment Centre Wales
    Bangor University
    Bangor
    LL57 2UW

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