GIS in the Classroom Blog 4: How can we use GIS to investigate coasts?

To say that coasts are important to humanity is something of an understatement. Coastal zones enabled our ancestors survive significant climate changes. The spread of humanity frequently happens between coasts and forty per cent of the world’s population live within 100 km (60 miles) of a coastline. It follows that geographers are very interested in this topic! How can GIS enhance our knowledge, understanding and management of coastal areas?

GIS can really help with visualisation and data analysis in the study of coastlines, by helping students to ‘see geography happen’. It can enhance their understanding of how coastal features are created, how they change and to think more deeply about the processes involved. It’s important that students can see the extent to which ‘theoretical’ geomorphology of coasts translates into ‘reality’. We’ll look at some examples including coastal erosion, deposition, management and fieldwork.

Firstly, we can use GIS to look at the impacts of coastal erosion. The UK has the dubious honour of the fastest eroding coastline in Europe, at Holderness in the East Riding of Yorkshire. You can use GIS to demonstrate just how fast. Using a swipe widget found in the Split Map app or National Library of Scotland’s ‘Side By Side’ option we can easily compare the present coastline with the way it was over a century ago, shown on the excellent Ordnance Survey 25 inch map of the time. We then use one of the measurement tools to show that the coast has retreated by over 230 metres, showing that the pace of erosion is over 2 metres per year. Furthermore, we can also see (and measure) the impact of coastal management where a stone groyne was installed in 1991, which has allowed an accumulation of beach material to provide some protection in the updrift area, markedly slowing erosion. However, this measure may have accelerated erosion downdrift from the groyne.

Secondly, we can study coastal deposition with geospatial resources. In the video above, we can see the spatio-temporal development of a spit called La Pointe d'Arçay (in France) using a timelapse of NASA Landsat images from 1984-2021 created in the Streamlit Timelapse app. There is speculation that the rapid growth of such depositional features in recent years may be an indirect consequence of climate change, which has provided greater wave energy.

Thirdly, GIS can be used to examine various methods of coastal management and evaluate the impacts. Historical aerial imagery informs analysis of the impacts of hard engineering intervention, in this case where offshore stone breakwaters were installed at Elmer, West Sussex in 2000. We can see what had happened by 2012 and compare this with 2020, using the Esri Wayback app.

Soft engineering can also be visualised (see clip above). Here Digimap for Schools was used to show the changes at Abbotts Hall Farm in Essex, where saltmarsh restoration has taken place.

Finally, geospatial resources can support primary fieldwork. As part of an investigation at Tankerton Bay in Kent, data was collected to find out the extent to which groynes trap sediment by measuring beach height. The georeferenced data was uploaded to a GIS web map to enable comparison of the downdrift and updrift height on either side of the groynes. A chart widget within the GIS app enabled the creation of bar charts to visualise the data.