Table of contents

4.6.1. Flood risk management for hydropower plants

Electricite de France (EDF) is the largest electricity producer in France. EDF has developed the Piano Key Weir (PKW) system, an improved flood discharge system that helps to release water safely from dams during heavy precipitation events. It provides an additional spillway to manage increased water flow without changing the maximum reservoir level. This is particularly relevant in the narrow gorges present in some of the alpine regions where PKWs have been installed. The primary benefit of such technology is to protect hydropower assets from damage while also reducing operational costs compared to alternative gate systems. PKWs can manage much higher flow levels and provide a safer solution than gated systems, with minimal risk of malfunction and easier evacuation of floating debris. PKWs also avoid human error, since they do not require human operators. . However, it may be unsuitable for some dam sites.

comments (0)

Releasing water safely from dams during floods or heavy precipitation presents a critical operational challenge. Past trends show an increase in extreme daily rainfall in southern France, which can lead to flash floods. This trend is expected to continue in the future. Snow and glacier melt are also expected to impact on dam inflow and outflow in the longer term. Glacier mass loss already shows a consistent acceleration across the Alps. The challenge for flood management at hydropower facilities is to prevent or minimise the impacts of dam-overtopping on downstream communities, property, agriculture and ecosystems, while also protecting the dams themselves against operational failure and other damage. Each hydropower dam presents different risk levels and the effectiveness of PKW systems must be evaluated separately in each case.

comments (0)

The Malarce dam (2.3 million m3, 16 MW), located in the department of Ardèche in the Auvergne-Rhône-Alpes region of France, features a PKW that increases the dam’s maximum discharge capacity to a total of 4600 m3/s. When dam water levels exceed the level in the inlet tanks, water automatically flows over the PKW into outlet tanks that run straight into the spillway channel and downstream. The PKW in the Malarce dam helps to reduce the risk of costly damage to dam infrastructure and to downstream communities.

comments (0)

The PKW has already been implemented in various hydropower facilities globally (e.g. in Algeria, the USA and South Africa), thanks to the collaborative approach of the original developers who did not patent this technology.

comments (0)