Integrated Storm Water Management


Current stormwater management practices consider just one unique solution, pipes. Either separate or combined, sewer systems are designed for maximum capacities based on scenarios up to 10-year storms. During the last decades, the pipe solution, also referred as conventional stormwater drainage, has been proved insufficient to manage all impacts related to urban runoff. Cities all over the world are facing common challenges of increasing stormwater floods, and degradation of natural resources and infrastructure caused by climate change and densified urban areas.

How land is initially developed has tremendous bearing on the prospective quantity and quality of urban streams.

Urban development removes the vegetation that intercepts, slows and returns precipitation to the air through evaporation and transpiration. These changes not only increase stormwater runoff, but also accelerate the rate at which runoff flows across the land. Conventional stormwater drainage systems such as gutters, storm sewers and lined channels designed to quickly carry runoff to rivers and streams, further exacerbate this effect.

Besides, the trend in land development towards densifying urban areas and increasing impervious surfaces has a direct impact on stormwater quality by increasing both the concentration and types of pollutants carried by runoff, and therefore the degradation of aquatic habitats.


The solution requires going beyond a narrow focus on a single problem to undertaking a comprehensive water resource protection strategy: recognizing the characteristics of specific water resources, understanding the relevant impacts, and tailoring a comprehensive array of tools to individual situations.

A combined use of multiple stormwater management solutions is not just possible, but also advisable to increase resilience to extreme weather and climate events. This is possible with an integrated stormwater management approach.

The iWater project team believes that our stormwater management solutions can be applied successfully in many other BSR cities, therefore we are proud to share with you our experience compiled in the Integrated Storm Water Management (ISWM) Guidelines elaborated by the iWater project.