a consistent suite of models for flood risk management

A CONSISTENT SUITE OF MODELS FOR FLOOD RISK MANAGEMENT R.M. Slomp Rijkswaterstaat F. Diermanse, H. de Waal (Deltares) J Stijnen (HKV) L.Wentholt & J Noort (STOWA) www.iahr2015.info Facebook: IAHR2015 Twitter:

@IAHR2015 #IAHR2015NL

Contents 1. Why we need consistent models for flood risk management and water management 2. Example : Lake Marken – Relationship between water management & flood risk 3. Different demands for models for policy evaluation and implementation 4. Example flood risk analysis and information for crisis management – –

Probabilistic modelling, Hydra concept Deltamodel workflow

5. Solutions /Choices -

WTI2017, common framework

6. Challenges for the future

1a) Why we need consistent models for flood risk management and water management: – a very complex system, many scientific fields – 25 independent organisations + many consultants, two large research institutes – Increasing flood risk: climate and economy – Increasing demands – irrigation and drainage

1b)

3600 km of primary dikes & dunes 15000 km of secondary dikes 55000 km of waterways, mostly with controlled water levels (locks, sluices, weirs, pumping stations)

2a) Lake Marken and Lake IJssel

Precipitation River discharges Pumping stations 700 m3/s Wadden Sea

+ pump

IJsselmeer 100 000 ha

Markermeer 50 000 ha sluicegate

Sluice gate

Afsluitdijk

Precipitation River discharges Pumping stations 70 m3/s

Houtribdijk

2b) An example determining how to manage lake Marken Daily outflow by gravitation 70 m3/s +precipitation: 10 mm/day = 100 m3/s

260 m3/s

100

total pumping stations+ precipitation for a T=100 year event: 400 m3/s

Figure with maximal discharges of sluice gates and pumping stations

2c ) Wave runup

Opleiding WDIJ

7

februari 2013

2d) Wind Set-up example, FEWS Lakes 7dec

2011

2e) An example of progress over time: modelling lake water levels

• Determining the statistics for lake water levels – 1996 • Generated time series (the lakes were created in 1976)

– 2006 • Extreme value statistics based on 30 years of data

– 2015 • A new statistical model using information on precipitation, discharges of rivers, wind speed and wind direction, and water levels in the Waddenzee.

3a) Different demands for models for policy evaluation and implementation

• Policy – needs answers fast

• Models have to be adaptable and consistent • Models have to capture the basic principles (without simplifying too much) – When we simplify too much wrong decisions are often made » e.g. modelling Flood risk only as a difference in design water levels

• Implementation – needs robust solutions • Models should be very reliable and consistent. • Large long term project need clear reference points over 10 to 15 years periods.

3b) Different demands for models for policy evaluation and implementation

• Policy – needs approximate answers fast, – Transparency during decision making – Investment decisions and evaluation of policy for : - Different climate scenario’s - Different measures or programmes • Implementation – needs robust solutions and clear references for long periods of time – Operation of water systems – Design of new pumping stations – Assessment of flood defences – Design of flood defences

4a) Procedure to determine flood risk and information for contingency plans

12

4.b) Probabilistic models Hydra preparation and application Preparation computations on physics database: water levels waves statistical information

Hydra hydraulic load (e.g. runup level) at standard freq.

Application

water defence information Hydra user

RWS & Deltares

area information

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Generic model chain 4.c) Probabilistic models, Hydra statistics

statistics

statistics

ref. waves

ref. wind

ref. water level

WIND MODEL

PROBABILISTIC MODEL

wind over water WATER LEVEL MODEL water levels and currents WAVE MODEL water levels

wave conditions

“Hydraulic Boundary Conditions” HYDRAULIC LOAD MODEL required strength statistics

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4.d) Delta model workflow for safety analysis Choice of # variables and # of computations

2d Model input + measures

Deltamodel WAQUA Sobek water levels

SWAN Brets. waves

Statistical data Database physics

Database tool Selection of maximum values

Water levels and waves

Analysis and post processing

Decimate heights

Delta-Instrumentarium

HYDRA : analysis

Damage function

Cost Benefit Analysis

Discharges, wind speed and wind direction, storm surges e.g.

DAM : design tool

Width of flood defence

KOSWAT Tool to elaborate costs

5a) Solutions • Step 1: Reduction of the number of models – If we need new functionality. We check if we can use an existing model as a starting point. We do not automatically make a new model – We integrated our models, we reduced the number of user interfaces, we included fast track applications for Policy Analysis.

• Step 2: Use of common framework, common libraries for failure modes and probabilistic analysis • Step 3: Working on consistent data definitions and exchange formats, for consistent workflows

5b) common frameworks, Development of WTI2017 software, combining different model lines: PC-ring, Hydra and DAM

6) Challenges

• The greatest challenge will be to keep the available and newly developed models consistent during the next policy change • The change in data protocols is largest risk • Researchers will continue their work and like to develop their own models. – Determining when to set up a new suite and not adding to the old will be a major decision.