Optimization of urban drainage systems

CTCN
Objective
Adaptation
Sectors
Water
Organisation
UNEP-DHI Partnership – Centre on Water and Environment
Technology group
Urban storm water management
CTCN Keyword Matches
Canals and drainage systems
Optimization of urban drainage systems
Urban infrastructure development
Urban storm water management

Description

Urban drainage and sewer systems are facing increasing pressures due to climate change and rapid urbanization rates. Common risks in these types of environments include sewer overflows due to heavy rainfall, and associated water contamination risks. 

Optimizing drainage systems aims to improve those already existing so that drainage overflows are minimized without having to expand the system. Computer simulation models improve real time operations using algorithms to evaluate system performance of, reveal deficiencies, identify high flood-risk areas, and illustrate optimal design improvement interventions such as optimal pump capacities, storage sizes, and locations, green spaces, etc. This helps managers meet desired system requirements to avoid overflows at the lowest possible costs and highest efficiency. Modern urban drainage systems are often co-optimized through linking them to other water management objectives such as improved recycling, groundwater recharge, water purification and recreational zone establishment  ( green spaces), therefore offering multiple benefits from a single investment. 

Implementation

Modelling and analysis of local climate change trends, rainfall patterns, population dynamics and land-use change and their effects on drainage and sewer systems is an important first for calculating overall system capacity and retention capacity. This identifies flood and overflow risk areas, in turn determining priority sections for intervention. This process can also benefit from involvement of a broader community of stakeholders, such as those from the land use planning and urban development sectors.   

In addition to these hydrological analyses, Socio-economic and environmental analyses can help identify optimization efforts to address local community needs of local communities, for example establishment of a recreational green area that also optimizes drainage systems.

Environmental Benefits

- Supports enhanced urban biodiversity and natural infiltration. 

- Improves groundwater recharge (infiltration systems such as trenches and permeable surfaces). 

- Decreases runoff rates and reduces the amount of pollution entering local watersheds. 

Socioeconomic Benefits

- Minimizes risk of flood events and subsequent damage, including water contamination.

- Reduces costs of physical system expansion and new treatment facilities.

- Results in recreational benefits that add to green space in urban settings, for example bioswales, wetlands, ponds, etc.

- Improves storage, provides effective treatment (improved water quality) and recycles systems, which  can reduce water stress on local reservoirs.  

Opportunities and Barriers

Opportunities:

-    Multiple benefits from a single investment – environmental and health benefits, as well as improved cost effectiveness and avoided costs

-    Hydraulic models and algorithm optimization can help create an integrated overview of urban drainage systems and improve real-time operation, and aligned system development across various dimensions

-    Climate change adaptation awareness integrated into local planning and urban development agenda

Barriers:

-    Optimization diagnosis requires an expert overview and system flow quantification, which may not be possible in certain locations

-    Mathematic models and estimation have limits 

-    Certain physical optimization interventions, such as permeable surfaces, require continuous maintenance 

Implementation considerations*

Technological maturity:         3-5

Initial investment:         2-3

Operational costs:         2-3

Implementation timeframe:     2-4

* This adaptation technology brief includes a general assessment of four dimensions relating to implementation of the technology. It represents an indicative assessment scale of 1-5 as follows:

Technological maturity: 1 - in early stages of research and development, to 5 – fully mature and widely used

Initial investment: 1 – very low cost, to 5 – very high cost investment needed to implement technology

Operational costs: 1 – very low/no cost, to 5 – very high costs of operation and maintenance

Implementation timeframe: 1 – very quick to implement and reach desired capacity, to 5 – significant time investments needed to establish and/or reach full capacity

This assessment is to be used as an indication only and is to be seen as relative to the other technologies included in this guide. More specific costs and timelines are to be identified as relevant for the specific technology and geography.

Sources and further information