Flood Protection Hollandsche IJssel Ina Konterman Rijkswaterstaat 25

Flood Protection Hollandsche IJssel Ina Konterman Rijkswaterstaat 25 Januari 2019

Hollandsche IJssel Which (combinations of) measures for flood protection Hollandsche IJssel are cost effective?

Scope of our project To analyze sets of measures for the flood protection of the Hollandsche IJssel and adapt the adaptation path of the Hollandsche IJssel if useful 4 steps of our study 1. System analysis Hollandsche IJssel 2. Study the possibilities of the Hollandsche IJssel Storm Surge Barrier 3. Analyse cost-effective sets of measures that can be taken (improvement of HIJ storm surge barrier, dikes, floodplains, waterlevel HIJ) and analyse external effects (ecology, shipping, etc. ) 4. Formulate adaptation path for the Hollandsche IJssel

1. System Analysis with SPR Framework System analysis

Possible measures flood reduction Hollandsche IJssel + Dike reinforcement + Use of floodplains + Improvement of HIJ storm surge barrier + Decrease waterlevel HIJ +. . Focus on HIJ storm surge barrier and waterlevel HIJ

1. Reduction of the failure rate of the SSB Hollandsche IJssel 1: 500, 1: 1000 and 1: 5000 per closure through all types of measures (back up of energy supply, emergency operation better designed, etc. ). ØFinal draft on possible options discussed in February 2019

2. Closing the barrier at low tide at the point of reversing current instead of just before high water Measure is very effective, little negative impact on shipping and road traffic

3. Limit the volume of water that enters the Hollandsche IJssel from the regional system as much as possible during critical conditions Approach for this study is ready and will be discussed in February

Impact of these measures on the waterlevel + Reproduction of results with a better hydraulic model just finished

Impact of these measures on the waterlevel + Reproduction of results with a better hydraulic model just finished

Cost assessment of measures First indications • Preliminary cost assessment of measures SSB HIJK bij RWS Cost Pool • What is on the agenda for the RWS Cost Pool: refine cost assessments (also operational costs) and cost assessments for measures regarding the regional water system

Cost assessment of measures First indications • Preliminary cost assessment of measures SSB HIJK bij RWS Cost Pool • What is on the agenda for the RWS Cost Pool: refine cost assessments (also operational costs) and cost assessments for measures regarding the regional water Investment costs improving SSB HIJK 10 million Euro system until 1: 5000 Savings in investments for dike reinforcements due to improvements SSB HIJ 50 million Euro Reduction of damage through flooding More than a billion Euro

Current status / preliminary conclusions + Take existing floodplains into account to calculate the strength of the dikes is very cost effective + In cases of abundant rain, filling up the regional watersystem, it is very useful to close the barrier at low tide at the point of reversing current instead of just before high water. + Investments in a better Storm Surge Barrier HIJ seems to be cost effective, independent of the size of improvements! + The study about the regional water system is complex and still needs a lot of attention

Focus of the work 2019 4 steps of our study 1. System analysis Hollandsche IJssel 2. Study the possibilities of the Hollandsche IJssel Storm Surge Barrier 3. Analyse cost-effective sets of measures that can be taken (improvement of HIJ storm surge barrier, dikes, floodplains, waterlevel HIJ) and analyse external effects (ecology, shipping, etc. ) 4. Formulate adaptation path for the Hollandsche IJssel

2. Selection, scoping & exploration – define the scope of the study Scope: To find an optimum on cost-effective sets of measures for the flood protection of the Hollandsche IJssel and adapt the adaptation path of the Hollandsche IJssel if useful 1. Update the system analysis Hollandsche IJssel 2. Study the possibilities of the Hollandsche IJssel Storm Surge Barrier 3. Analyse cost-effective sets of measures that can be taken (improvement of HIJ storm surge barrier, dikes, floodplains, waterlevel HIJ) and analyse external effects (ecology, shipping, etc. )