Extreme river events: Rijkswaterstaat International Event

The challenge
According to the latest IPCC (2021) report and research on snow and glacier melt in the Alps, river discharges will become more extreme. Winter discharges are predicted to increase, summer discharges to decrease, and periods of low discharge to last longer. Intense rainfall will cause more or less unpredicted flooding. There is a complex relationship between (extreme) discharges and weather models, leading to uncertainty about future conditions. The relationship between extreme discharges and morphological changes is even more difficult to predict and impacts many services the river provides (e.g. navigation, cooling water energy/industry, water supply, biodiversity, fish migration, recreation, livability). And finally sea level rise has to be taken into account.
Rijkswaterstaat has managed the main Dutch river systems for 225 years. The above challenges illustrate a need to rethink how we manage our rivers in the future, notably in periods of prolonged low discharges. Do we need a plan B?

The discussion will focus on

Challenges regarding international (cross border) integrated water resource management.
Current state of the knowledge, data monitoring and modelling: what do we know, and what do we need?
Watershed-wide application of solutions and decisions to mitigate the effects of climate change.
Challenges in maintaining - or changing - the services a river system provides on catchment scale, avoiding or reversing technological lock-ins.

Goal
The goals are to:
o   Reach a common understanding of mutual challenges
o   Define gaps in knowledge and reinforce topics we already work on together
o   Identify new collaboration opportunities, regarding the above challenges, where possible linking to (international) policy is needed.

Time	Description
14.00	Opening, welcome and relevance of session for Rijkswaterstaat Karin Weustink, Director Rijkswaterstaat South Netherlands
14.10	Setting the scene. Changes in river systems and river management in the UK Mark Bowers, Deputy Director for Readiness & Response, Environment Agency, UK
14.30	Upstream river basin management and climate change; Challenges for Swiss river managers? Petra Schmocker Fackel, Head of hydrological basics section Swiss Federal Office for the Environment FOEN
14.50	What does all this mean for a delta river manager as RWS, from a national and international perspective? Harold van Waveren, Principal advisor flood risk management Rijkswaterstaat , Chair national crisis management team floods and droughts
15.10	Break
15.30	Workshop with small groups 1. What are the issues to address in the short and longer term for RWS. Where is RWS vulnerable? 2. ‘Bring your own river’: how are you addressing these issues/subjects in the short- and long term? Are these also your blind spots or are there other subjects? Small group discussions will be held around 5 themes.
16.40	Conclusions and wrap up Karin Weustink and moderators
17.00	Walk to Museum Prinsenhof for museum visit, reception and opening dinner

We will start our journey upstream the river Rhine, close to the border with Germany, and decent down the river. In Lent the river area along Rhine’s main branch, the Waal, will be visited. Extreme flooding risks here have been mitigated in the Room for the River intervention in this urbanized area, creating new nature and recreation areas. Aspects of River bed erosion and shipping will also be addressed in our visit. In Driel we will visit the weir lock in the Nederrijn as an important object to partially mitigate water scarcity problems in the Netherlands, especially maintaining drinking water reserves in the future. Finally we will visit the “langsdammen” along the Waal, close to Tiel. Here dams have been created parallel to the river in order to reduce erosion, a better groundwater-surface water interaction and improved biodiversity habitats.

Time	Description
08.00	Assemble at Expo Arsenaal
08.30	Bus ride to Nijmegen Lent During the bus ride we will give an introduction on extreme river events Rhine, Netherlands and measures taken so far.
10.30	Field visit to Nijmegen Lent We will visit the upstream Rhine in the Netherlands and discuss flooding problems, Room for the River and erosion problems. Hosts: Evelien van Eijsbergen (senior advisor River management) and Ralph Schielen (senior advisor River systems)
12.00	Bus ride to Driel (lunch will be provided in the bus)
12.40	Field visit to Stuwcomplex Driel Hosts: Evelien van Eijsbergen (senior advisor River management) and Ralph Schielen (senior advisor River systems)
13.50	Bus ride from Driel to Tiel
14.25	Field visit to Langsdammen (longitudinal dams) near Tiel We will discuss low and high water, morphology and erosion reduction and groundwater-surface water interaction. Host: Saskia van Vuren, Rijkswaterstaat
15.40	Bus ride back to Delft. Afterwards you may enjoy drinks in Expo Arsenaal and exchange experiences.

International symposium on adaptive management of urbanized deltas

Extreme River Events: and what does it mean for the river manager?