Browsing by Author "Zhang, Jin"

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Open Access
Investigations on urban river regulation and ecological rehabilitation measures : case of Shenzhen River in China
(2014) Zhang, Jin; Wieprecht, Silke (Prof. Dr.-Ing.)
River systems, as a major component of the water environment, have the most interactions with human beings in many ways, especially along with social development and population growth, as well as the intense utilization of the river systems by humans, a series of major ecological environmental problems have arisen in recent years. Therefore, river system regulation and management has become a crucial focus point of research. Although the integrated river management is the preferred and most commonly accepted method that is applied in water resources management, a significant problem is that there is a shortage of integrated river ecological research which focuses specifically on urban rivers. The current problems governing urban river regulation and ecological status rehabilitation can be summarised into the following points: The definitions of urban and rural rivers are still not clarified; Interactions between urban and rural rivers are neglected; Need for an applicable mapping method for driving the urban river health index; Limited availability of input data sources, especially in the developing world for assessment and management of environmental problems. This research aims to study on the above addressed issues, to clarify the characteristics of urban rivers and to find an applicable method of assessing their health status. In this PhD research, the identification of urban and rural river reaches is studied as the first main purpose, a generic conceptual model namely the Urban-Rural River Continuum Identification System (URRCI) is developed. Reference of this system is to review the classification of urbanization, in order to distinguish whether the surveyed river section belongs to urban river or rural river, and further to solve the problem of the unclear definition of urban rivers. The second important issue has been addressed in this PhD research is to focus on urban river regulation, aiming to set up an advanced urban river ecological health assessment system which can be applied easily. The case study area of Shenzhen River in China has been selected to build up the database in order to establish and prove this new improved river health assessment system, and simulate effective rehabilitation measurements scenarios. The fuzzy logic approach is integrated into the fish habitat model CASiMiR, which is developed at the University of Stuttgart, Institute for Modelling Hydraulic and Environmental Systems, and is receiving a continuously growing acceptance in Europe and worldwide. The customized tool took advantage of an existing fuzzy inference calculator, which is integrated within the ArcGIS, thereby allowing direct data integration from various geospatial sources as input parameters and the presentation of output in the form of spatial and temporal maps. Indeed, the system of fuzzy rules (rulebase) can contain more than one input and one output parameter. The interaction between the urban river reach and the rural river reach is also identified as the third addressed objective. The integrated health status index is generated for both the urban and rural reaches base on the ArcGis based simulation. One expression is developed to calculate the health index for each of the urban and rural river stretches which are identified by the urban-rural river continuum identification system. The study on the Urban/Rural river interaction helps to find out what the thresholds of these main parameters in the urban river reach are, so that the urban river will not bring any stress onto the whole river system, which will affect the habitat suitability, and the most important is to lead a direction on the specific influenced plot and effective rehabilitation measures. As the last main objective of this PhD research, several mitigation scenarios are planned for the simulation of river rehabilitation. From the assessment of the urban/rural river ecological health status, bank/bed protection and riparian vegetation are the two parameters which have the most influence. Removal of bank protection and the enhancement of riparian vegetation have been carried out as the river rehabilitation measures individually and combined as well, from a comparison of the enhanced integrated river health index for each urban/rural stretch with different fuzzy membership functions, we can see that when the integrated fish suitability index has more weight in the river’s ecological health assessment system, the subsequent river ecological rehabilitation measures have less impact. When the integrated fish suitability index, bank protection and riparian vegetation have equal importance in the river’s ecological health assessment system, river enhancement is more effective. On the other hand, parameters related to the water body itself refer more to the stands of hydraulics and hydrology, which are not easy to change. So in this research they are not considered for improvement. The implementation in Shenzhen River shows that the advanced urban/rural River Ecological Health Assessment System was successfully established. It is easy to use and interpret since it adopts the standard governing parameters of river health that are widely accepted all over the globe. This approach allows rapid scenario analysis for large regions and has the potential to be used as a practical tool for the assessment of urban river ecological health by policy-makers and scientists.