Monitoring and Research
What Monitoring and Research are we doing or planning to do?
An important aspect of any pilot project is to provide learning and experience for others who want to undertake similar work.
Although there is currently no budget for formal monitoring of any of the works installed as part of the project, we have undertaken some informal baseline work to try to understand how our Large Woody Debris Structures will perform and evolve over time. We have formed a working group to focus specifically on monitoring meeting to discuss potential work that we can undertake ourselves and in partnership with others. We are also discussing with the Environment Agency how we can build on work they are undertaking at a national level to provide evidence for the benefits of Natural Flood Management.
In some areas of the catchment, we are able to compare historical flows under a given rainfall event with flows and levels we now experience after installation of natural flood management measures. The Slad valley in particular provides a good opportunity for comparison because it has a number of flow gauges that have been collecting data over a reasonable time period before we carried out work.
On March 9th 2016, the Stroud Valleys had approximately 35-40mm of rain over 12 hours. This is roughly half the monthly total expected for March. The EA were able to compare this event with a similar one that occurred in November 2012, before the RSuDS project started. We looked for an event of similar magnitude and intensity, but importantly, we also looked at how saturated the ground was before the rainfall occurred.
The comparison of the two events is shown on the graph below:
The graph shows the two peaks aligned in the 10 hours over the event and shows a very substantial reduction in peak level. We have checked the gauges to ensure that there were no technical errors or problems and also compared the 2012 data with other events pre-construction The November 2012 graph is a consistent level of response. We are satisfied that the data, for both events is reliable.
As with any comparison it is important to bear in mind that no two events will ever be identical, we looked for two rain events that were closely comparable in terms of total rainfall, duration, intensity, preceding conditions and seasonality. We have also looked at ground saturation levels. In both cases, the soil moisture deficit is zero, indicating full saturation in both cases. It is important to note that the base flow level for 2012 was higher, indicating greater preceding ground saturation, and therefore potential run-off.
However, it is also important to note that the total rainfall over the 10 hours prior to the peak was higher in the 2016 event.
We would welcome any ideas or suggestions for research from academic institutions. The projects in the Stroud Valleys now provide a significant opportunity for those wishing to undertake research on the different benefits of natural flood management. Please contact the project officer, Chris Uttley at firstname.lastname@example.org if you would like to discuss research proposals.