More and more people live in cities and by 2050 two thirds of the global population is expected to live in a city. Because of this urban migration, cities generally need to densify and expand. The densification often leads to more impermeable surface, such as asphalt and concrete, which increases the risk of flash floods in city centres. The expansion may require that historically flood-prone areas need to be exploited, which increases the flood risk also in suburbs and peripheral parts. In parallel with this trend, climate change is expected to intensify the hydrological cycle and for example lead to heavier rainfall. When combined, these changes are likely to significantly increase the risk of flooding in urban and peri-urban areas. There is an urgent need for research towards a better understanding, modelling and forecasting of urban flood risk under these changes.
Bridging the gap between urban and rural hydrology
Traditionally, urban hydrology (and hydraulics) has often focused on very short (≤1 h) intensive rain and central city centers with a very large proportion of impermeable surfaces. However, recently studies have shown that severe floods require longer rain (for example 2-4 h) and contribution to drainage also from permeable but water-saturated surfaces. There is an increased need for R & D in the border between traditional urban and traditional rural (that is, in pure natural land) hydrology. This R & D includes, for example, analysis of precipitation processes on different scales, and their connection to various urban hydrological risks. It also includes the development of methods and tools for urban hydrological risk assessment with different time horizons, ranging from forecasts for the next hours or days to climate projections for the rest of the century.
Research and Development questions
How are precipitation processes on different scales connected to urban hydrological risk and adaptation?
How can high hydrological simulation and forecasting be developed to better support urban hydrological risk assessment?
How will urban hydrological risks be affected by climate change?
Our core publications in this Scientific focus
Olsson, J., Bengtsson, L., Pers, B.C., Berg, P., Pechlivanidis, I., and H. Körnich (2017) Distance-dependent depth-duration analysis in high-resolution hydro-meteorological ensemble forecasting: a case study in Malmö, Sweden. Environ. Model. Softw., 93, 381-397,.
Olsson, J., Arheimer, B., Borris, M., Donnelly, C., Foster, K., Nikulin, G., Persson, M., Perttu, A.-M., Uvo, C.B., Viklander, M., and W. Yang (2016) Hydrological climate change impact assessment at small and large scales: key messages from recent progress in Sweden, Climate, 4, 39,.
Berg, P., Norin, L., and J. Olsson (2016) Creation of a high resolution precipitation data set by merging gridded gauge data and radar observations for Sweden, J. Hydrol., 541, 6-13,.
Olsson, J., Berg, P., and A. Kawamura (2015) Impact of RCM spatial resolution on the reproduction of local, sub-daily precipitation, J. Hydrometeorol., 16, 534–547,
Rana, A., Foster, K., Bosshard, T., Olsson, J., and L. Bengtsson (2014) Impact of climate change on rainfall over Mumbai using Distribution-Based Scaling of Global Climate Model projections, J. Hydrol. Reg. Stud., 1, 107-128,.
Olsson, J., and K. Foster (2014) Short-term precipitation extremes in regional climate simulations for Sweden, Hydrol. Res., 45.3, 479-489,.
Olsson, J., Simonsson, L., and M. Ridal (2014) Rainfall nowcasting: predictability of short-term extremes in Sweden, Urban Water J., 11,.
Olsson, J., Amaguchi, H., Alsterhag, E., Dåverhög, M., Adrian, P.-E., and A. Kawamura (2013) Adaptation to climate change impacts on urban flooding: a case study in Arvika, Sweden, Clim. Chang., 116, 231-247,.
Olsson, J., Gidhagen, L., Gamerith, V., Gruber, G., Hoppe, H., and P. Kutschera (2012) Downscaling of short-term precipitation from Regional Climate Models for sustainable urban planning, Sustainability, 4, 866-887,.
Amaguchi, H., Kawamura, A., Olsson, J., and T. Takasaki (2012) Development and testing of a distributed urban storm runoff event model with a vector-based catchment delineation, J. Hydrol., 420–421, 205-215,.
Olsson, J., Willén, U., and A. Kawamura (2012) Downscaling extreme Regional Climate Model (RCM) precipitation for urban hydrological applications, Hydrol. Res., 43, 341-351,.
Olsson, J., Berggren, K., Olofsson, M., and M. Viklander (2009) Applying climate model precipitation scenarios for urban hydrological assessment: a case study in Kalmar City, Sweden, Atmos. Res., 92, 364-375,.