Evaluation of the Stadswerven designs
6.2 Evaluation of the Stadswerven designs
The Stadswerven area can be characterised as type ‘risk zone 2’. When the river exceeds a certain water level, the area is almost immediately flooded, although the water depths are small, the duration of flooding is short and the water velocities are relatively low (< 0.25 m/s, a velocity at which wading through the water is still safe). These favourable circumstances make it possible to set an ambitious target, aiming at minimal disruption of daily life.
The Stadswerven concepts were evaluated using a selection of the criteria from Table
6.1. The evaluation focuses on the stronger and weaker points of the different concepts and provides a way to compare the concepts. The choice of criteria was based on the relevance for Stadswerven, on the availability of calculation results to argue the criteria and on the aspects in which the concepts are distinguishing.
Table 6.2
Evaluation of the Stadswerven concepts
Mount
Integrated Watersteps floodwall
Safety level
+ Maximum reached velocities and depths are
+ within safety limits
Anticipation on climate change
+ Safety river under average conditions
+ Safe havens within area
+ Anticipation on possible failure of floodwall
Incorporation of flood proof infrastructure
+ Controlled flooding
+ All aspects are assessed for a water level up to 3.4m +NAP, the foreseen design water level
for 2100. : Not applicable to the design concept
+ : complies with the criterion - : does not comply with the criterion
All concepts are designed such that they comply with the safety aspects. The concepts prescribe a safe infrastructure network called a lifeline. The integrated floodwall design for Stadswerven does not incorporate safe havens in the northern area, but this area is connected by this lifeline to the main land where higher grounds are situated.
The Mount concept will not flood up to the design water level foreseen for 2100 (NAP +3.4m). It should be taken into consideration though, that only up to the design level, a safe situation is guaranteed.
If the water levels exceed the design level, the area could become flooded. No anticipation to flooding is incorporated in the design, resulting in an uncontrolled flooding. This also applies to the higher grounds within the other two design concepts.
For the Integrated floodwall concept it should be taken into account that there is a possibility of failure of the floodwall. A failure can cause flooding effects similar to the breaching of a dike. The design concept leaves room for adjusted building concepts in the area behind the floodwall.
The Watersteps concepts comply with all criteria. The concept anticipates on flooding. Water is welcomed within the area adding to the attractiveness of the sight.
The design concepts prove that Urban Flood Management for areas not protected by dikes is feasible. But the design concepts as developed for Stadswerven are not applicable to all areas. The character of an area determines the possible flood proof concept ranging from ‘prevention of casualties’ to ‘no disturbance of daily life’. The concepts as developed for Stadswerven are at least applicable for areas similar to Stadswerven, thus where the maximum water depths and velocities are relatively low, flood duration is short and the floods prediction time is sufficient to prepare for the flood.
The design concepts show that for areas which at first sight seem an unsafe environment for urban development, with flood proof building concepts can be adapted to become a safe and pleasant living environment.