Author(s): Junshuang Yu
Linked Author(s):
Keywords: Land cover changes; Surface runoff management; Green infrastructure; Natural flood management
Abstract: Changes in land use and land cover can significantly influence the hydrological characteristics of an area. This study focuses on the River Irwell catchment in northwest England, highlighting how different changes to land cover can have distinct impacts on regional runoff. The study classifies and analyses land cover types within the catchment and identifies a ‘2-year return period’ from the depth-duration-frequency (DDF) curve as a reasonable return period based on historical records. Reasonable model calculations were used to analyse the changes in runoff generation for each type of land cover in the catchment. Trends in land cover indicate that the proportion of built-up areas and hills, heaths and bogs in the Irwell Valley increased significantly over the study period (1990–2019). Conversely, the percentage of grassland cover decreased significantly over the study period. This change in land cover was accompanied by a clear upward trend in the generation of surface runoff within the catchment. In response to the increased flood risk, this study offers options for targeted surface runoff management in both upstream catchments and urban built-up areas. The adoption of wastewater treatment systems, including green infrastructure in built-up urban areas, is recommended. To determine the effectiveness of green infrastructure for runoff management, this study assessed its potential in the area based on aerial imagery and climate projection data. The study found that while green infrastructure, including roof gardens, can mitigate increases in runoff generation, its practical role and potential is limited to assisting in runoff management. Natural Flood Management (NFM) measures based on upstream catchments have greater potential, but they are still limited by instabilities and slow effectiveness cycles. This study recommends a combination of options for surface runoff mitigation strategies. The first is to update environmental change and climate prediction data and upgrade existing flood protection works accordingly. The second is to design soil and water conservation systems, plan NFM and traditional flood protection projects and build new sponge cities using both ‘soft engineering’ and ‘hard engineering’ approaches.
Year: 2024