Adaptation to extreme rainfall; demonstration of FHVI to prevent damage by urban pluvial flooding

PROJECT DESCRIPTION

BACKGROUND

Climate change scenarios predict more frequent and larger extremes in rainfall. Already, cities in the EU face damage from pluvial flooding. Damages will increase due to climate change and continuing urbanisation. Urban pluvial flooding is a major problem that urgently requires effective, sustainable and cost-effective solutions.

Putten regularly encounters climate change-induced problems with pluvial flooding. During heavy rainfall, large parts of the village are flooded. Heavy rainfall also regularly leads to discharge of untreated sewage into Lake Veluwe (“Veluwemeer”) directly from the town, or from a forced bypass of the wastewater treatment plant.

Putten has developed a comprehensive strategy to reduce disturbance and damage from pluvial flooding. Decoupling and infiltration of rainwater is at the heart of this strategy. The town has started decoupling and infiltration using state-of-the-art conventional technologies, and is interested in the Fast High Volume Infiltration (FHVI) technology and its capabilities for infiltration and damage prevention.

FHVI directly injects rainwater into a permeable layer or aquifer, at a rate much higher than conventional injection. Thus, discharge capacity of urban rainwater can be vastly improved. FHVI is known from continuous recirculation in the construction sector, using pumps to bring previously pumped up water back into the ground as quickly as possible. A major innovation in the case of rainwater infiltration is the elimination of the pumps and driving infiltration with the pressure of the water column in the infiltration tube only.

With its variable terrain, soil conditions and groundwater levels, a demonstration of FHVI would deliver results relevant to many areas in the EU.

Small-scale testing has confirmed the ability of FHVI to deal with peak precipitation levels of T10 events (occurring once every 10 years). The technique must now be taken to the demonstration stage on a scale representative for use in a large city, to prove its added value and reliability. Importantly, the city council of Putten has also recently invested in conventional infiltration techniques in part of the town, which can serve as a benchmark for FHVI.

OBJECTIVES

LIFE AERFIT aims to demonstrate an innovative adaptation technology to prevent damage from urban pluvial flooding. The main objective is to prove that FHVI is an effective adaptation strategy. In this regard, through the project’s actions and applications, the two main objectives are:

To provide sound evidence of the effectiveness of FHVI to deal with extreme rainfall, as well as its wide applicability (i.e. replicability) and favourable implementation costs; and

To disseminate the results and the applicability potential of the project to authorities and professionals throughout the EU.

Expected results: The project expects to achieve the following results:

A successful demonstration of the FHVI technique as a cost-effective adaptation strategy for climate change (extreme rainfall) and prevention of damage from pluvial flooding in urban areas;

A reduction of frequency, duration and level of flooding events in Putten, the target being no water on the street at peak precipitation levels of a T10 event corresponding to a total quantity of 36 mm per hour;

Improved quality of effluent at the wastewater treatment plant;

Reduction of 5 200 m3/yr of discharge of excessive, untreated mixed rain and sewer water;

Prevention of desiccation, through 46 800 m3/yr of water added to groundwater reserves;

Resilience to spills (key in this respect is that a spill in a FHVI infiltration well can be ‘reversed’, i.e. used to pump back spills that penetrated the groundwater);

Dissemination of project and monitoring results to stakeholders and target audiences;

Creation of interest of at least 10 other European cities and municipalities to implement the FHVI technique to adapt to climate change; and

Provision of a blueprint, facilitating rapid replication and transferability to other European cities and municipalities.