5 Conclusions and Limitations
5.1 Conclusions
This study has reached the following conclusions for the Wairau catchment:
1. Design Storm vs. Dynamic Modelling:
c. The dynamic modelling approach yields lower flows (10% - 15% lower for the Wairau catchment) and fewer flooded locations than the design storm model for the 'Present' climate.
d. This decrease in flooded locations and flows results in the prediction of fewer potential stormwater upgrades with the dynamic modelling approach for the present climate scenario (50% less channel affected over the whole Wairau catchment - refer Table 4-1).
2. 'Present' Climate vs. Potential 'Future' Climate:
d. Both the design storm and dynamic modelling approaches predict a greater number of stormwater infrastructure issues as a consequence of climate change (36% increase in length of channel affected under the design storm modelling, 6% increase under the dynamic modelling).
e. Climate change effects appear greater when using a design storm modelling approach.
f. Catchment characteristics and infrastructure (i.e soil characteristics, presence of ponds) can have a significant influence on modelled flows and water levels.
5.2 Study Limitations
The following notes are provided to identify individual catchment characteristics of the Wairau catchment that may have had an influence on modelling results:
a. The large number of in-line ponds influences catchment storage and upper-catchment flows, and is particularly noticeable for the dynamic modelling. Given the differences between dynamic time series and design storm modelling it is difficult to verify the correct imlementation of the design storm modelling approach to simulate climate change.
b. The large infrastructure and wide flood plains in the catchment minimise the effects of increased flows on water levels.
c. The model calibration was undertaken at one point in the mid-catchment. It is difficult therefore to accurately isolate the effects of individual catchments (i.e. pervious vs. impervious).
