Urban Riverbank Research Articles

都市河川における望ましい植生とは ―堤防に咲く“菜の花”から考える―

都市河川における望ましい植生とは ―堤防に咲く“菜の花”から考える―

Establishing a spatial map of health risk assessment for recreational fishing in a highly urbanized watershed

Recreational fishing is a popular activity in many urbanized watersheds. When river water is incidentally ingested during fishing sessions, substantial waterborne fecal contamination can cause adverse health effects. This study aims to spatially map health risks for recreational fishers caused by waterborne Escherichia coli (E. coli) in the highly urbanized Tamsui River watershed. First, indicator kriging was used to probabilistically estimate the distributions of waterborne E. coli and determine the conditional cumulative distribution function (CCDF). Subsequently, to propagate the parameter variability, Monte Carlo simulation was adopted to characterize the ingestion rate and exposure duration for recreational fishers and E. coli realizations were generated using random fields on the basis of the estimated CCDF. Finally, after the three parameters were combined, the approximate beta-Poisson dose–response function was employed to quantitatively determine potential risks to recreational fishers in the Tamsui River and its tributaries. The analysis results revealed that the risks of recreational fishing exceed an acceptable level of 8 infections per 1000 fishers per day at several urban river courses. Therefore, recreational fishing activities in urban riverbanks pose a substantial health threat. Recreational fishing in urban riverbanks should be limited before the construction of complete sanitary sewer systems. The river mouth and certain upstream river sections are suitable for the development of recreational fishing.

Visualising the riverbank

Drawing on ethnographic observation of a tract of urban riverbank in the city of Trento, in northern Italy, we attempt to link phenomenological observation of social interaction in public places with larger political concerns about contemporary urban public space. While agreeing with Low et al. (Rethinking Urban Parks: Public Space & Cultural Diversity. Austin: University of Texas Press, 2005) that in order to foster public spaces it is necessary to accommodate the differences in the ways social classes and ethnic groups use and value urban sites, we also argue that one should be wary of planning hubris—which can occur in even ‘good-willed’ planning, and leads to the creation of domesticated and formalised, but also inherently restricted, spaces for encountering differences.

Urban riverbank residents’ evaluation of flood evacuation policies in Winnipeg, Manitoba, Canada

The results of a discrete choice experiment (DCE) as a part of a survey among the urban riverbank residents on the Red River in Winnipeg, Manitoba, Canada, indicated that the risk of over-dike flooding, set at 2 ft above the 1997 flood water level, was a significant determinant of both voluntary and mandatory evacuation, compared to those set at the 1996 or 1997 levels. Mandatory evacuation was more preferred over voluntary evacuation when the likelihood of flooding was at its most severe, and the opposite relationship was the case when the likelihood was low. The notification time for evacuation, suggested as 1, 2, and 4 days, proved to be an insignificant attribute, whereas the respondents indicated significant preference for full flood compensation over an offer of either 80% or 90% flood relief, irrespective of the alternatives of voluntary or mandatory evacuation.