Impacts of flooding on coastal water quality from sewage, agricultural and industrial effluent

31 July 2023

Periodic flooding as a result of heavy rainfall is becoming more frequent in the western English Channel. This is because the heating of inland water and the sea is causing more evapo-transpiration which results in high rainfall, and then flooding.

These flooding events can carry agricultural fertilisers, sewage effluent and, in some locations, heavy metals from mining tailing ponds from the rivers to the coast - posing a risk to human health and to the environment through the deposition of high nutrients, suspended material, viruses and bacteria to the coast. This in turn can be deleterious to seagrass beds and mud flats, which are important areas for depositing and drawing down carbon dioxide from the atmosphere.

Above: These two satellite images show (upper panel) phytoplankton biomass (chlorophyll-a concentrations [mg m-3]) and (lower panel) total suspended matter (TSM) concentrations [mg l-1] in the River Tamar, Plymouth Sound and coastal waters on 28 February 2021. Image credit: Dr Liz Atwood. These types of satellite data will be used in the Vis4Sea project to track flooding events. 

The Vis4Sea project intends to measure the impacts of these flooding events, using a wealth of measurements to piece together the bigger picture. . The project is a partnership between Plymouth Marine Laboratory (PML), the Commonwealth Scientific and Industrial Research Organisation, an Australian Government agency responsible for scientific research, Pixalytics Ltd., and Specto-Natura Ltd.

With scientific advancements, there is an incredible amount of data available to marine scientists to study the environment. These include measurements made from samples collected by boats, data from marine moorings, buoys and unmanned vessels as well as satellite data. For satellite data, this is now available at very high resolution so that a range of parameters and the intricate details of these in rivers, estuaries and the coast can be easily seen from space.

However, given the variety different sources of data available, it can be difficult to analyse them in a coherent, consistent and easily findable format. 

To piece together the data measuring the water quality in the Plymouth Sound, scientists involved in the project will build a cohesive Open Data Cube to facilitate the combination of in situ sampling, automated sensor network and multi-source, multi-sensor drone and satellite data.
 

What is a data cube?

Data Cubes are gridded and stacked arrays of different data sets, that can be interrogated easily and efficiently by scientists. Australia’s national science agency, CSIRO, has developed open data cubes, such as the AquaWatch data system, which allows multiple users to easily interact with large archives of data. Through this platform, computer code, known as machine learning, can be used to turn some of the data sets into water quality parameters, to allow the assessment of whether coastal water is 'clean' or 'poor' quality.

Above: Visual concept of the ‘Virtual Satellite Constellation’ of AquaWatch

Lead PML Scientist Dr Gavin Tilstone said about the project: “Flooding events are becoming more common and can result in the discharge of sewage effluent to the coast, which can affect pristine marine habitats around the Plymouth Sound.”

"We are looking forward to utilising the recent developments in data cubes and machine learning to track these events in the local area, and assess their impacts on water quality, mud flats and sea grass beds.”

Lessons learnt from the Western Channel Observatory will be applied to the Fitzroy River in Australia, where periodic flooding is also becoming more frequent. It will also provide maps of areas that are not affected by flooding to allow conservation groups to regenerate Seagrass beds.

Dr Samantha Lavender,  Managing Director of Pixalytics Ltd. said about the project and partnership that “As an SME, it’s exciting to be working in collaboration with UK and Australian partners on highly relevant issues linked to water quality.”

The information generated by the project will be freely available to end-users to help the monitoring and management of water quality in the Plymouth Sound catchment, and the project data and results will be showcased to interested parties through an end of project stakeholder event.

Vis4Sea stands for VISualisation and Assessment of water quality using an Open Data Cube FOR the weStern English channel and has been funded through the UK Science and Technology Facilities Council EO4AgroClimate programme under  the UK Research and Innovation, a non-departmental public body of the Government of the UK that directs research and innovation funding.
 

Project information

Project start: August 2023  |  Project end: March 2025
Funder: UKRI Science and Technology Facilities Council through the EO4AgroClimate program.
Project Title: Vis4Sea - VISualisation and Assessment of water quality using an Open Data Cube FOR the weStern English chAnnel.
Principal Investigator: Dr Gavin Tilstone
Project Partners: Nagur Cherukuru and Tim Malthus, CSIRO, Australia; Samantha Lavender, Pixalytics Ltd., UK; Geoff Smith, Specto-Natura Ltd., UK.
Other participants from PML: Dr Dan Clewley, Silvia Pardo, Dr Tom Jordan, Dr Liz Atwood, Dr James Harding, Dr Sarah Breimann, Malcolm Woodward, Dr Helen Parry, Aser Mata, Matthew Taylor, Bethany Wilkinson.