What role do gully pots play in sustainable urban drainage?
Our cities and receiving water priorities have changed and so should also our perception of gully pots. As our cities evolve to achieve sustainability, we need to gain a better understanding of the performance and impacts of gully pots to ensure their role within wider sustainable drainage strategies is evidence-based.
Following discussions with stakeholders, Haoyu Wei will focus on evaluating the performance of gully pots under current and future climate scenarios. The results will indicate possibilities for safer operation today and support future discussions on the role of gully pots - as part of a sustainable urban drainage strategy.
Despite their ubiquity, the performance efficiency of gully pots has been challenged for a long time. Variations in in-pot sedimentation process rates are reported, calling into questioning their ability to meet their design purpose. For example, field studies indicate gully pots only capture up to 30% of inflow suspended loads. This poor performance, however, stems from two main reasons: infrequent gully pot maintenance operations and increasing extreme wet weathers.
This leads to a major challenge for city stormwater managers: finding a balance between the frequency of gully pot emptying operations and a limited budget. Challenges in accessing gully pots during maintenance as well as the increasing labour costs only complicate the situation further. For example, it is reported that only 5% of the gully pots are emptied annually in Oslo, Norway. Coupled with increasing frequency of heavy rainfall events, climate change will certainly affect our current urban drainage system, with its impacts on gully pot performance, the research focus of this study.
Developing new knowledge on the role of gully pots as a “short-term sink and long-term source” was chosen as our starting point. In our recently submitted paper, the remobilisation of previously settled sediments under different weather regimes and gully pot maintenance conditions was explored (see figure). This initial work provided new understanding on the conditions under which gully pots discharge sediments and hence their potential role as a source of pollution during extreme rainfall events. The results generated are of relevance to water regulators in gully pots maintenance planning, particularly in relation to the development of programmes of measures required to contribute to receiving waters achieving EU Water Framework compliance.
