Earlier in December ’24, I posted a draft map on Bioregioning Tayside’s online community forum for the project – Feeding Tayside through the Climate Crisis [1]. The map was in response to a query from Clare Cooper as to whether data on soils could contribute to new work in that project that will map the locations of the many community-led, food growing groups in the region. An inventory of soils would be part of a wider review of the cultural, historical and biophysical environments associated with the locations.
[Post recently published – liable to minor editing …]
Data from national soil survey collected and held by the James Hutton Institute and the Scottish Government [2] could offer such background information on the locations where the groups were working. At this early stage – and rather than approach GIS specialists among previous colleagues – I wondered what might be done with free software and open-source data.
Watercourses
A defining feature of the Tayside Bioregion is the vast network of streams and rivers that combine to form the huge flows of water into broad lowland straths (valleys) such as Strathmore and then into the Tay estuary between Perth and Dundee. These watercourses have modified and in some cases formed the soils of the region, particularly in the low-lying areas now used for arable and grass agriculture.
Fig. 1 Watercourses, mostly in the Tay catchment flowing into Strathmore and then into the Tay estuary between Perth and Dundee (lower right). Watercourse shapefile by OS Open Data [3] displayed on a Google Earth Pro [4] greyscale background, map by www.curvedflatlands.co.uk.
Uploading the Ordnance Survey’s open-source (free to use) data [3] to Google Earth Pro [4] resulted in a map of the waterways, shown first on a grey-scale background in Fig. 1. Those waterways flowing mainly from north to south, and also west to east at the left-hand side, are part of the Tay catchment which enters the sea through the Tay estuary at the lower right. Those flowing west to east at the upper right, including the River Dee, continue directly east to the North Sea. Strathmore – which holds much of the agricultural land of the region – is watered by the many rivers arising in the hills to its north.
When the background is displayed in colour (Fig. 2), most of the main watercourses move through green areas, which indicate mainly cropped or grazing land, mostly at the bottom of glens and straths. The junctions of several watercourses are indicated. For example Tummel / Tay is where the River Tummel flowing from the north-west joins the River Tay flowing from the west.
Fig. 2 Watercourses from the lower part of Fig. 1 displayed on a coloured background: green indicating grazing and arable land; brown, hills, mountains and moorland. Circles indicate junctions of some rivers. Watercourse shapefile by OS Open Data [3] displayed on Google Earth Pro, map by www.curvedflatlands.co.uk).
Soil classification
A comprehensive and detailed account of the soils in Scotland has been compiled through survey and research over many decades by organisations that are now part of the James Hutton Institute. Much of the information has been made available online for download and use free of charge [2].
The World Reference Base (WRB) for soils was chosen as the dataset to use for the present purpose. The WRB classifies soils throughout the world in the same terms, such as Histosol, Cambisol and Podzol. In the WRB for Scotland, each of the main categories is further refined by two ‘qualifiers’.
Uploading the WRB data to Google Earth Pro together with the watercourse shapefile gave the result in Fig. 3. The map reveals some intriguing alignments between watercourses and soil types, but needs some further work. For example, the same soil type is not always displayed in the same colour, resulting in too many colours! A work in progress!
Fig. 3 Watercourse [3] and WRB soil [2] shapefiles combined on Google Earth Pro. To aid cross-reference, two of the river-junctions in Fig. 2 are indicated; the location of Dundee is shown near where the Tay estuary meets the North Sea; and the approximate centre of the map is marked by the arrow to Bridge of Cally where the River Ardle and Blackwater meet. Map by G R Squire at curvedflatlands.co.uk.
Shape-shifting
The main watercourses in this region were formed over a long geological history. They were found in much their present form by people migrating northwards on retreat of the last ice around 11,500 years ago. In more recent times, streams and rivers have been re-shaped for a range of purposes including capture and storage of water for domestic and industrial use.
Common among recent developments are the changes made for agricultural improvement. Natural watercourses rarely follow straight lines. They bend and meander, slowing the flow. After heavy rain, the water floods over land, leaving it sodden for much of the year and an unwelcoming place for crops and grass.
The monastic estates, expanding northwards during the 1100s, left one of the first written accounts of managing water to improve productivity. They cut or deepened channels to drain water from marsh and bog, as on the Carse of Gowrie by the Tay estuary west of Dundee. Deep channels taking water into the Tay estuary allowed water in the upper soil to move down under gravity, with the result that air could enter the soil, which in turn allowed microbes to proliferate and roots to penetrate. Re-shaping was intensified centuries later to allow the new machinery of the 1700s to run in long, straight lines.
There are many examples of re-shaping watercourses in the area shown in the maps above. Take, for example, the junction of the Kerbet and the Dean in Fig. 2. The following is from Kinnettles Kist (2000) published by Kinnettles Heritage Group [5]: “The point at which the Kerbet enters the Dean was altered during the construction of the Great Drain or “Canal” by Strathmore Estates between 1766 and 1767. A terminal meander of the Kerbet, which is still discernable on the ground, was replaced by a straight section, which enters the Dean further to the east than the original river.”
Re-shaping of watercourses for agriculture, and also during the construction of transport networks and housing estates, has consequences. For example, Kinnettles Kist reports that in the previous 5 to 10 years (before the year 2000) , the general water level had dropped, the water became cloudier (presumably with eroded soil), more algae appeared on the stones (possibly due to fertiliser run-off) and flooding was more severe under heavy rain. Changes such as these are still happening throughout the lower areas of the catchment.
Next
Mapping watercourses and soils could contribute to defining the general environment of the locations used by local food growers and cooperatives in Tayside. On possible problem is that, given the small areas occupied by many growers, some local variation in conditions might not be captured in such datasets. Therefore, additional on-site characterising of soil in particular would be needed.
There are several online guides for soil, including Visual Evaluation of Soil Structure (VESS) by Bruce Ball and colleagues [6]. It is feasible for the new project to develop a general method that could be used consistently by growers in the project to assess and improve their soils.
Contact for this page: geoff.squire@outlook.com
Sources / Links
[1] Bioregioning Tayside web: updates, reports and links at Food System Transformation including the filmed 2023 conference Feeding Tayside through the Climate Crisis and recent developments through Recipes for Action.
[2] James Hutton Institute offer open access resources on soils: introduction at Soil maps which gives link to a range of mapped data.
More on the World Reference Base for Scotland – map shown to the right – at SpatialData.gov.scot which points to reports on how the WRB classifications were made for the UK.
[3] Ordnance Survey (OS) open source (free to use) data at OS Open Rivers, part of the OS Data Hub.
[4] Google Earth Pro
[5] Kinnettles and District Heritage Group published Kinnettles Kist, an account of the Parish. The whole book is available for free download (9.2 Mb PDF) under ‘Books’ at the Kinnettles and District Heritage Group web site and, if preferred, individual chapters can be read online. For example, the quotes above can be viewed at Chapter 2. The Kerbet and its valley.
[6] Guidance on soil: e.g. Good Soil Guide; GetGrowing Scotland; Visual Evaluation of Soil Structure (VESS) and related work by Bruce Ball and colleagues is linked on the Living Field web at VESS.