Demonstrating the need to simultaneously implement all water sensitive design methods for aquatic ecosystem health.

Area of Science:

• Environmental Science
• Urban Planning
• Ecology

Background:

• Water Sensitive Design (WSD), also known as Low Impact Urban Design and Development (LIUDD), offers practices to manage the water cycle and boost biodiversity.
• Previous research often assessed individual WSD techniques (e.g., stormwater retention, reduced impervious surfaces) in isolation.
• Urban developers frequently implement WSD practices piecemeal, potentially overlooking the synergistic effects needed for ecosystem health.

Purpose of the Study:

• To evaluate the ecosystem responses of streams to the simultaneous implementation of multiple WSD practices.
• To compare these responses across two different urban densities within paired sub-catchments.
• To identify the impact of comprehensive versus isolated WSD application on aquatic ecosystems.

Main Methods:

• Monitoring stream ecosystem health using a biotic index.
• Implementing a comprehensive suite of WSD 'building blocks' in paired sub-catchments.
• Conducting paired sub-catchment studies at two distinct urban densities in Auckland, New Zealand.

Main Results:

• Significant differences in stream ecosystem health were observed between treatment and control sub-catchments at both urban densities.
• Failure to implement all WSD techniques or to apply them appropriately led to observable stream ecosystem degradation.
• The study highlights the consequences of incomplete WSD implementation on local streams and the marine receiving environment.

Conclusions:

• Simultaneous and comprehensive application of WSD practices is essential for maintaining and improving stream ecosystem health.
• Isolated implementation of WSD techniques is insufficient and can lead to ecosystem degradation.
• Effective WSD requires a holistic approach, integrating all 'building blocks' to prevent negative impacts on aquatic and marine environments.