The Modelling Process

To all those interested:

The modelling process involved in the case of Uckfield, and in fact any similar study, is a long one with several important steps before any potential results can be achieved and analysed. It is also important that any results are viewed in the context of model uncertainty.

Therefore by updating you all on my progress, hopefully you will be able to understand and follow the steps that I take in the modelling process, as well as my masters study in general.

I am currently in the process of familiarising myself with the Overflow model. This involes gaining and developing a general understanding of how the model works through running basic instructions and looking at what output the model can provide. This learning stage is very important before I can look at the model more in-depth.

In addition to learning to use this model, as part of my masters degree, I am also developing a greater understanding of the more broad issues relating to the Uckfield case, particularly in terms of flood attenuation.

As allways, feel free to e-mail me with any questions you may have

Thanks, Ed

Some background to the study; my role and the wider context

As this blog may potentially reach a slightly wider audience I thought it appropriate to explain in more detail my study for those that are not aware of it:

Context

The town of Uckfield, Sussex experiences regular flooding, with the flood event in 2000 being particular large. In the subsequent flood report;

(http://www.wealden.gov.uk/Planning_and_building_control/Development_Control/Uckfield%20Appeals/WD-2006-2173/Water%20%28Drainage%20and%20Flood%20Risk%29/Appendix%20W6/Appendix%20W6%20-%20Extract%20from%20BBV%20Report%20on%20Sussex%20Ouse%20Flooding.pdf)

it was stated the rainfall in a 16 hour period of 11/12th October in the Uck catchment was estimated to be a 1 in 150 year event.


Further info on 2000 flood;
http://www.geography.org.uk/resources/flooding/Uckfield

Following this event, a flood wall was built to reduce flood risk for 30 properties, however this wall is expected to be designed for a 10-year event;
http://www.environment-agency.gov.uk/news/112405.aspx

My project comes at a time when there is much less money available for hard engineering approaches to flood protection such as large flood walls. There is also the realisation that such flood protection measures can have the effect of increasing flood risk downstream. In addition to this, in the event of flood wall failure, flooding can be even worse.

Therefore if it were possible to reduce flooding through the implementation of smaller-scale, diffuse, flood attenuation measures throughout the catchment this could potentially be very desirable.

For this study such measures will take the form of catchment riparian intervention measures (CRIMs). These CRIMs will most likely consist of a debris dam and riparian vegetation, with the aim of essentially slowing down water during high flow periods.

The idea behind the CRIMs is increasing the roughness of the channel and floodplain. Increasing channel roughness has the effect of reducing channel conveyance, causing small-scale local flooding. By increasing water storage in upstream areas of the catchment, the flood peak downsteam can potentially be reduced.

The hydrological model to be used is Overflow. The Overflow model is a reduced complexity model. The thinking behind use of such a model is that pysically-based models, for example SWAT, require a large number of parameters to represent physical properties of a catchment.

There is an uncertainty associated with each parameter - therefore such models may potentially be more uncertain than simpler models. A reduced complexity model also has the benefit of allowing relatively quick simulations to be carried out allowing quicker evaluation of interventions in the catchment.

My role in this study follows previous (and continuing) work with regards to the development of the model in Pickering and Uckfield, and also to the 'Knowledge Controversies' project:
http://knowledge-controversies.ouce.ox.ac.uk/

To summarise my role;

The aims of my masters research are:
1.To model the effects of CRIMs, placed throughout the catchment, on the flood peak downstream at Uckfield.
2. To evaluate the performance of a suitable reduced complexity model for assessing the impacts of small scale riparian woodland interventions
3. To develop an intervention strategy with the aim to reduce downstream flood risk, taking into account feasibility (e.g. biodiversity objectives)

Ed