Climate changes impacts on subtropical urban drainage with low impact developments

Abstract

Low impact developments (LID) have been used to mitigate the effects of urbanization on the hydrological cycle. However, there is a lack of studies on LID performance in subtropical climates and under potential impacts of climate change scenarios. This dissertation evaluated the impacts of two climate change scenarios (RCP 4.5 and 8.5) on urban drainage with pollutants and their effect on LID practice efficiency located in a subtropical climate, with Cfa classification according to Köppen and Geiger. First, the inlet quantity and quality parameters were calibrated. The buildup/washoff model was evaluated, comparing load calibration and concentration of pollutants: chemical oxygen demand (COD), total organic carbon (TOC), phosphate (PO4) (NH3), iron (Fe), cadmium (Cd) and zinc (Zn). Pollutant washing was studied in the area of the bioretention catchment using historical rainfall data between 2013 and 2017, analyzing the influence of the buildup/washoff parameters of each pollutant in the input mass. Afterwards, Eta-5x5km (INPE) climate change scenarios were disaggregated to 5-minute intervals by the modified Bartlett-Lewis method. The disaggregated series was used to estimate the impacts of climate change on urban drainage into the bioretention. Therefore, a simple model, developed specifically for the study bioretention cell, was used to estimate the qualitative-quantitative efficiencies of each period of the climate change scenarios. According to the data acquired from INPE, climate change will result in a fall in the volume of rainfall in São Carlos, resulting in lower volumes of surface runoff. The impacts on pollutant washing, however, vary according to the buildup/washoff parameters, explained by a sensitivity analysis. Climate change does not affect the bioretention quantitative efficiency very much: 81.7% from 1980 to 1999 to 81.4% and 81.3% from 2080 to 2099 for CPR scenarios 4.5 and 8.5. The pollutant removal efficiencies, as well as the washing, depend on buildup/washoff characteristics. One of the main consequences of climate change is a drop in the runoff quality. However, even with quantitative efficiency being maintained, bioretention is capable of mitigating this increase in the concentration of pollutants in urban drainage. Thus, the LID will help preserve the quality of downstream rivers, whose volumes will already have diminished by the decrease in rainfall volume.

Nature-Based Solutions and Real-Time Control: Challenges and Opportunities

“…This approach, however, has been applied to roughly estimate pollutant accumulation as a function of antecedent dry days and pollutant transport in terms of exponential or power fitness functions calibrated with observations [98,99]. However, these parameters are site sensitive, especially because local conditions, such as wind direction and speed, road characteristics, land-use and land-cover, can play a vital role in the spatial variation of pollutant accumulation [100]. In [101], the use of total mean daily loads (TMDL) or event mean concentration (EMC) as an alternative to high-resolution pollutographs is recommended due to the high variance of pollutant conditions.…”

Low Impact Development practices in the context of United Nations Sustainable Development Goals: A new concept, lessons learned and challenges

“…This additional volume must be considered to design LID structures regarding long-term flood mitigation. The ΔP|climate will also lead to different process of pollutant build up and wash off, affecting the pollutant load in the runoff (ΔL|climate) (Liu et al, 2016;Liu et al, 2017;Lago, Macedo & Mendiondo, 2018). ET is also affected by the difference in precipitation and temperature regimes (ΔET|climate).…”

Aspectos hidrológicos-hidráulicos e avaliação da eficiência de biorretenções: modelos, princípios e critérios de projeto de técnicas compensatórias de 3ª geração

“…Além disso, Lago et al (2018a) obtiveram para a biorretenção em estudo, eficiência de retenção próxima a 80%, quantificando a resiliência das TCs perante as mudanças climáticas em climas subtropicais. De acordo com Lago et al (2018b), os cenários de mudanças climáticas afetarão nos volumes de precipitação. Portanto, afetarão as concentrações de poluentes afluentes aos corpos receptores em São Carlos, sugerindo que medidas deverão ser tomadas, tendo em vista o cenário RCP-8.5 que projeta a diminuição de 51% do volume anual de chuvas para o ano de 2100.…”