River Re-naturalization - a Nature-based Solution for Climate Change in Urban Areas

The subject of the article is river management and their reconstruction in connection with the need to adapt urban areas to climate change. The article presents a fragment of a wider research. The aim of the study is to identify and indicate the main directions of activities undertaken in the field of river reconstruction, based on the analysis of documents and literature on the subject. The case study of the Wandle River - one of the tributaries of the Thames, running through heavily urbanized areas in London, is an example of the restoration of the river. In this case, the use of natural solutions improved: flood and drought risk management, stormwater retention, inhabitants' access to the river and biodiversity of natural habitats associated with the river.

Developing Climate Resilience in Aridlands Using Rock Detention Structures as Green Infrastructure

The potential of ecological restoration and green infrastructure has been long suggested in the literature as adaptation strategies for a changing climate, with an emphasis on revegetation and, more recently, carbon sequestration and stormwater management. Tree planting and “natural” stormwater detention structures such as bioswales, stormwater detention basins, and sediment traps are popular approaches. However, the experimental verification of performance for these investments is scarce and does not address rock detention structures specifically. This 3-year study investigates the infiltration, peak flow mitigation, and microclimate performance of a natural wash stormwater retention installation using one-rock dams in an urban park in Phoenix, Arizona, USA. Field data collected during the study do not depict change in the hydrogeomorphology. However, hydrologic modeling, using data collected from the field, portrays decreases in peak flows and increases in infiltration at the treated sites. Additionally, we observe a lengthening of microclimate cooling effects following rainfall events, as compared with the untreated sites. In this urban arid land setting, the prospect that rock detention structures themselves could reduce warming or heat effects is promising.

Application of dynamic and conceptual models for simulating flow hydrographs in an urbanized catchment under conditions of controlled outflow from stormwater tanks

The main aim of the research presented in the work was to assess the usefulness of the dynamic SWMM (stormwater management model) and the conceptual SBUH (Santa Barbara Urban Hydrograph) model for simulating and predicting flow hydrographs in a small urbanized catchment under conditions of controlled (using valves) outflow from stormwater retention tanks in response to rainfall events. Most of the analyzed catchment of the Służewiecki Stream consists of the area beneath F. Chopin International Airport in Warsaw. A further aim of the study was the development of method for indicating the concentration time for a given rainfall–runoff event, where the influence of delaying the outflow of stormwater from the catchment as a result of its retention in tanks on the value of this parameter will be accounted for. The values of the median of absolute errors, obtained in a simulation using the SWMM in relation to peak flows and hydrograph volumes for the analyzed events, were 15.4 and 18.4%, respectively. The adequate values of simulation errors, obtained in the SBUH model using concentration times determined according to the developed method, were 11.4 and 15.4%. Satisfactory results of simulations were received using both models.

Evaluation of nutrient retention and sediment deposition in two urban stormwater retention ponds

Stormwater ponds have been implemented in many municipalities to control urban runoff and retain pollutants, such as nutrients and suspended solids. Two stormwater ponds in Toronto, Ontario were evaluated for their ability to retain nutrients and suspended solids and were also used to investigate mechanisms by which stormwater ponds remove nutrient pollutants, including the importance of deposition and internal loading. Over the entire study period, Hydro Pond East (HEP) retained 1415 mg of total suspended solids (TSS) and MAT retained 1127 mg of TSS. Both Hydro East Pond (HEP) and Mattamy Rouge (MAT) were net exporters of phosphorus (P) over the entire season, with 6.35 mol or 0.20 kg and 53.9 mol or 1.67 kg exported, respectively. HEP had net retention of 2672 mol or 37.4 kg of nitrogen (N) but MAT exported 264 mol or 3.7 kg of nitrogen over the entire study. This study has demonstrated that stormwater ponds have the ability to provide retention of nutrients and TSS, but their function may be enhanced as they may become exporters. However, the amount of nutrients exported was extremely low and may have been driven by the anomalously dry 2016 year in Toronto. Further research should be done on these same ponds to observe how they may perform under an anomalously wet year (e.g. 2017). There is a need for a future model to synthesize the data from literature on stormwater ponds to better understand their function to better help local water managers determine if these ponds are needed and how they may need to enhance their function.

Evaluation of nutrient retention and sediment deposition in two urban stormwater retention ponds

Stormwater ponds have been implemented in many municipalities to control urban runoff and retain pollutants, such as nutrients and suspended solids. Two stormwater ponds in Toronto, Ontario were evaluated for their ability to retain nutrients and suspended solids and were also used to investigate mechanisms by which stormwater ponds remove nutrient pollutants, including the importance of deposition and internal loading. Over the entire study period, Hydro Pond East (HEP) retained 1415 mg of total suspended solids (TSS) and MAT retained 1127 mg of TSS. Both Hydro East Pond (HEP) and Mattamy Rouge (MAT) were net exporters of phosphorus (P) over the entire season, with 6.35 mol or 0.20 kg and 53.9 mol or 1.67 kg exported, respectively. HEP had net retention of 2672 mol or 37.4 kg of nitrogen (N) but MAT exported 264 mol or 3.7 kg of nitrogen over the entire study. This study has demonstrated that stormwater ponds have the ability to provide retention of nutrients and TSS, but their function may be enhanced as they may become exporters. However, the amount of nutrients exported was extremely low and may have been driven by the anomalously dry 2016 year in Toronto. Further research should be done on these same ponds to observe how they may perform under an anomalously wet year (e.g. 2017). There is a need for a future model to synthesize the data from literature on stormwater ponds to better understand their function to better help local water managers determine if these ponds are needed and how they may need to enhance their function.

Evaluating the potential stormwater retention of a living retaining wall system

Redesigning standard revetment or retaining walls to capture stormwater could increase the use of living walls and, thus, expand their beneficial impacts, including greening underutilized space. This study evaluated the potential stormwater retention and percent plant coverage of an experimental wall surface for six treatments (five vegetated Sedum treatments and an unplanted ‘control’ wall) on 18 circular living retaining wall systems designed from a standard retaining wall system. Percent stormwater retention, which compared effective precipitation volumes with stormwater runoff volumes, was quantified for 81 storm events from July 2010 to September 2011. Living retaining wall systems planted with S. (Phedimus) takesimensis retained stormwater more effectively than the unplanted wall and other planted treatments, including walls planted with S. spurium, mixed Sedum species, and S. kamtschaticum. Plant surface coverage of the living retaining wall system was the greatest when planted with mixed Sedum species, S. spurium, and S. kamtschaticum. Overall this study demonstrates that properly designed living retaining wall systems may be able to be used as a best management practice for stormwater retention in urban areas. Further study could determine the performance of living retaining walls with a more conventional design (i.e., single aspect vs. four aspects against a slope), over a longer time period, walls planted with other vegetated treatments, and walls featuring different fill and plant materials.

Nature-Based Solutions for Flood Mitigation and Resilience in Urban Areas

Urban areas face several environmental problems and risks related to water management, such as floods and degradation of water quality, enhancing population vulnerability and threatening urban sustainability. These problems are expected to be exacerbated with increasing urbanization and climate change, which leads to higher frequency and intensity of hydrometeorological extremes. Moving towards more flood resilient cities has proven a major challenge, particularly considering the high concentration of population and economic activities and, thus, high pressure on limited available space. Nature-based solutions (NBS) in urban areas favour stormwater retention, infiltration, and filtration, contributing to flood mitigation and enhancement of water quality. The effectiveness of different NBS on stormwater management, however, is influenced by design and placement aspects, but a network of connected NBS elements can improve flood mitigation and enhance urban resilience. Stronger evidence of the advantages of NBS, however, is still required to overcome the current challenges and barriers impairing their wider implementation in urban areas.