Overview

Heavy rain and storm water events such as those in the Ahr valley in Germany in 2021 or in Pakistan, Australia or South Africa in 2022 cause streams to swell to raging torrents. They flood roads, destroy houses and bridges and important infrastructure. Yet not only do they cause damage worth billions – they also lead to loss of life. They occur suddenly, and can only be predicted at short notice. Due to climate change, these events will continue to increase in frequency and severity worldwide.

41 experts from 16 cities and eight countries accepted the joint invitation of Connective Cities with Stadtentwässerungsbetriebe Köln (StEB Köln) and United Cities and Local Governments (UCLG) to this dialogue event in December 2022.

Twelve practical examples from five countries formed the starting point for an intensive peer consultation on which approaches can be used to minimise the risks of heavy rain and storm water events for people and municipal infrastructure. Existing projects were enriched and new project ideas emerged.

Keynotes

Integrated Water Resources Management
Betül Türkeri, Mercator-IPC (Istanbul Policy Center) Fellow
Integrated Water Resources Management (IWRM) analyses the interaction of surface water, aquifers and coastal waters, with a view to managing them sustainably in order to promote social and economic development, and ensure ecosystem functionality.
[pdf, 330 kb]

“Catalyzing” Water Sensitive Cities through Capacity Development
Julie Perkins, Global Water Operators' Partnerships Alliance (GWOPA)
So far, water supply and sanitation services are far from reaching all people. Peer consulting in Water Operators' Partnerships (WOPs) can be a crucial lever to improve capacity here.
[pdf, 3,4 mb, in Englisch]

Results

During the two-and-a-half-day event, there was a close as well as diverse exchange of expertise among colleagues, for example on a financing concept for an improved drinking water and wastewater system in Kigali, Rwanda; on decentralised flood protection and the involvement of the population in the planning of flood protection measures in the Ahr Valley, Germany; on improving drainage infrastructure in Mwanza, Tanzania and in Zarqa, Jordan; on preventing flood amnesia - the forgetting of flood risks over generations; on integrating sponge city measures into existing infrastructure; and on a pilot tree-trenches programme in Banjul, Gambia.

Some general lessons also emerged, such as:

1. Flood protection along river courses cannot only start in the river valleys, but also in the upstream river tributaries.
2. It takes many small measures on a regular basis to prevent flood amnesia.
3. Successful pilot projects and positive cost-benefit analyses can help to convince the population as well as decision-makers for changes in existing infrastructure, for example with regard to a sponge city concept.
4. Sponge cities help to protect groundwater resources through more infiltration areas and become more resilient to prolonged droughts and hot spells, but provide only limited protection during  very extreme storm and heavy rainfall events.
5. If residents' own resources are limited to get involved in an organised way in the development of flood protection concepts, it can be helpful to involve external partners such as universities, mediators and/or journalists.
6. The direct involvement of local residents in the construction work for improved drainage infrastructure not only generates local income, but also increases the acceptance and thus the sustainability of the measures.

The event was concluded with a tour of pumping stations and flood protection measures of StEB Cologne.

A more detailed description of the dialogue processes can be found in the report on the conference (see below).