GIS in the Classroom Blog 3: How Can We Use GIS to Investigate Rivers
What do long profiles and cross profiles really look like? When studying rivers, GIS can help students gain a deeper understanding of how river features are created, think more deeply about the processes involved and appreciate the extent to which the ‘theoretical’ geomorphology translates into ‘reality’. We’ll look at some examples including long and cross profiles, meander development, river case studies and flood management.
Using ‘elevation profiles’ provides an effective way to apply learning to novel situations and deepen understanding. The web maps in ArcGIS Online are embedded with data points showing elevation above or below sea level which can be harnessed to analyse topography by creating apps such as Rivers – Elevation Profiles shown below (or 3D version). Long profiles can be generated with one click on the river courses shown, such as the River Parrett in south-west England. Other river channel courses be created manually or using the ‘Trace Downstream’ Analysis Tool in web maps.
A cross profile is even easier to create, because the transect line is shorter. If it’s not possible for students to do this themselves, a profile can be created in advance, captured with a screen recorder and used for teaching or independent tasks. Alistair Hamill (@lcgeography) demonstrates how in one of his exemplary resources using ArcGIS Online for several rivers in Northern Ireland, such as the Colin River and Glendun River, including guidance which can easily be applied to local rivers anywhere.
Andy Funnell (@GeogAndy) has compiled very helpful ‘Oven Ready’ Case Studies including rivers and flood management created by himself and colleagues in different schools using Google Earth. They’ve very generously shared the ‘kml’ files, to enable users to view and customise the data, ranging from continental scale (e.g. Mississippi) to regional (e.g. River Dee; River Tees) to local (e.g. Knock River; Somerset Levels). Andy’s resource on The Ganges Delta in Bangladesh is part of a world tour of twelve major deltas.
One of the best GIS viewers is provided by National Library of Scotland Maps. It’s particularly useful for studying rivers. Their georeferenced maps include a range of tools for studying spatiotemporal change in landscapes. In the example below the ‘Spy’ viewer enables us to ‘see through’ Bing imagery to compare with the landscape recorded over 60 years ago by the OS 1:25,000 1937-1961 layer. Powerful geography is revealed as we see how legacy boundaries follow former meanders of the River Dee along the border between Wales and England, since abandoned by the main channel as ox-bows.
Another valuable ‘geospatial’ resource for the study of rivers is aerial and satellite imagery (remote sensing), providing visualisations of spatiotemporal change, once again providing students with opportunities to ‘see geography happen’ and consider how the processes and features they have learned about operate in practice.
Animated remote sensing imagery has been accessible via Google Earth Engine Timelapse since 2013, but recently, more detailed imagery and timelapse apps have become available such as the excellent Streamlit Timelapse by Professor Qiusheng Wu which includes customising options for selecting filters. Here we can see the development of meanders along a river in the Peruvian rainforest using NASA Landsat data 1984-2022. The vegetation appears red, because plants reflect more near-infrared light than green. Apart from the spectacular appearance of an ox-bow lake, there is scope to apply learning about erosion, deposition, meander migration and braiding as well, not to mention the way that remote sensing works!
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