|Titel:||Ecosystem services of urban floodplain soils under changing climate and water management||Sprache:||Englisch||Autor*in:||Kalinski, Kira||Schlagwörter:||urban floodplain soils; ecosystem services; water retention; pollutant retention; carbon storage||GND-Schlagwörter:||F6||Erscheinungsdatum:||2021||Tag der mündlichen Prüfung:||2021-02-08||Zusammenfassung:||
With this study, a high potential for the optimization of the ecosystem services of urban floodplain soils was identified.
Scholz et al. (2012) named water retention, pollutant retention and carbon storage as the most important ecosystem services of active floodplain soils. Flood events can be mitigated, ecosystems and people protected from high levels of pollution and carbon storage enlarged. Especially in cities, these ecosystem services are increasingly exposed to the stressors of urbanization and climate change. Floodplains are being decimated in favor of settlement construction, with a simultaneous increase in heavy rain and flood events. So far, ecosystem services in urban floodplain soils and their processes have not been sufficiently researched. Previous studies have examined individual ecosystem services in urban floodplains focusing on strategies to improve urban planning concepts. The aim of this study is to analyze the most important ecosystem services of soils in urban floodplains combined. Based on the gained results, optimization strategies of each ecosystem service considering increasing stressors of urbanization and climate change are developed.
The urban floodplain soils of the Kollau River and the Dove‐Elbe River in the City of Hamburg were investigated for this purpose. The current state of water retention, pollutant retention, and carbon storage were analyzed and controlling factors on the respective ecosystem services identified. Field and laboratory experiments were performed to improve the process understanding of (i) accumulation processes of pollutants, (ii) water balances and sources during flood events, and (iii) mineralization of organic materials in urban floodplain soils.
In the Kollau area, significantly higher levels of pollutants were analyzed in the sediments of water retention ponds compared to the topsoils of the floodplains. As an example, zinc levels of 74.35 mg kg‐1 in the topsoils and 266.71 mg kg‐1 in the sediments were measured. Within the ponds, highest accumulation masses were calculated in the shallow water zones overgrown with a plant cover. By increasing and extending these zones in water retention ponds, the pollutant retention can be optimized.
Depending on location and season, groundwater levels varied from 0 to 110 cm below surface and water storage capacities ranged from 16 to 265 cm within 1 m soil depth in the Kollau area. Optimal water storage capacities were determined in soils with low water contents, low groundwater levels, and a sandy soil texture. These soils were identified especially at the edges of the designated floodplains. Water retention of bank soils was calculated for different bank morphologies and scenarios consisting of climate, urbanization, and soil condition. Flat bank morphologies, sandy soil substrate and low water content favor water retention of bank soils. Overall, only a portion of runoff can be retained during flood events in bank soils. The flood wave can be flattened, but not completely retained. For an optimal water retention in floodplain soils, the designated floodplains should be extended considering small‐scale differences of soil properties and bank areas flatten at suitable sites.
In the soils of the Kollau and Dove‐Elbe areas, low to very high carbon pools between 0.44 kg m‐2 and 260.99 kg m‐2 were analyzed. Fossil peat bands, burial of former topsoils, and technogenic organic rich substrates, are the main reasons for the high carbon storages. Water contents and groundwater levels mainly influences these carbon pools. In addition, carbon mineralization is controlled by the composition of the organic matter components, which seems to be influenced by urban factors. Higher mineralization rates were determined for litter from an urban site compared to litter of a rural surrounding. Existing high carbon pools can be maintained and increased by creating near‐natural floodplain areas with high water contents in urban floodplain soils.
Following on from previous studies, this study presents a combination of the important ecosystem services of pollutant retention, water retention and carbon storage of urban floodplain soils. The optimization of these ecosystem services could be developed based on the gained results. Through the specific redesign of floodplains and water retention ponds, planning concepts such as water management can be improved and ecological flood protection in cities further advanced. The creation of near‐natural floodplains and the associated increase in biodiversity and provision of recreational areas represents synergies. Conflicts arise in the simultaneous implementation of mutually exclusive optimization strategies. For example, low soil water contents were derived to optimize water retention and high soil water contents were derived to optimize carbon storage. In the future, urban planning processes should focus on providing sufficient floodplain areas in cities for the optimization of its ecosystem services. This process can positively influence the important mitigation of climate change and urbanization in cities.
|Enthalten in den Sammlungen:||Elektronische Dissertationen und Habilitationen|
geprüft am 01.08.2021
geprüft am 01.08.2021