It is common practice in any field of policy that the performance of implemented
measures is periodically or continuously evaluated in terms of the original
objectives. Such evaluation can yield new insights and information, which could
give rise to adjusting the strategy as appropriate (NRC, 1995). This post-implementation
evaluation must be distinguished from the evaluation exercise that is done to
identify the most appropriate technology. The latter can be considered pre-implementation
evaluation and is part of the planning and design phase (Section
Effective evaluation requires a reliable set of data or indicators, to be collected at some regular interval using an appropriate monitoring system. Evaluation will often be necessary for decades and the monitoring should be planned accordingly. There is limited experience of such long-term monitoring, so in many situations it is unclear which are the most appropriate data or indicators (Basher, 1999). For physical systems, experience can be drawn from countries where the coast has been monitored for long periods. In The Netherlands, for example, the position of high water has been collected annually for nearly a century and cross-shore profiles have been measured annually since 1963 (Verhagen, 1989; Wijnberg and Terwindt, 1995; Hinton et al., 1999). Observations of the "natural" evolution of the coast allow trends to be reliably estimated and hence the impact of human interventions on the coast (breakwaters, nourishment, etc.) to be evaluated.
In general, monitoring technologies are the same as those used for initial description of the coastal system. They are listed in the upper part of Table 15.1 and discussed by Morang et al. (1997a), Larson et al. (1997), Morang et al. (1997b) and Gorman et al. (1998). After a number of years, a new climate-impact assessment, using updated climatic and socio-economic scenarios and including consideration of adaptive capacity and non-climate stresses, could serve to see if overall coastal vulnerability to climate variability and change has been successfully reduced.
Other reports in this collection