Presentation by Bobby Russell (Deltares) at the Symposium Models and decision-making in the wake of climate uncertainties, during the Deltares Software Days - Kampala 2023 (DSD-Kampala 2023). Wednesday, 4 October 2023, Kampala, Uganda.

1. Modelling in support of decision
making
Bobby Russell
4 October 2023

2. A ‘Model’ is a simplified conceptual representation
of part of the hydrological cycle.
Leads to two important questions:
1. What question do you want to answer with the model?
2. What does the end-user want to do with the model or model results?

3. The Msimbazi River story
Supporting investment planning in Dar es Salaam, Tanzania

4. Msimbazi River
4
• Severe floods in 2009, 2010, 2011, 2014,
2015, 2017 and 2018.
• Very disruptive to transportation and
threat to life.
• Threat to recent and future urban
infrastructure investments.
Government of Tanzania and the World Bank
had two questions:
1. What is causing/exacerbating the
flooding?
2. What can we do about it?
All Photos: Chris Morgan World Bank

5. Hydrological
model
Hydraulic
model
Impact
model
Model workflow
5
wflow catchment
modelling software
D-Flow FM of
Delft3D FM Suite 1D2D
Delft-FIAT tool for
quantifying ‘damage’
caused by flooding.
Rainfall-runoff
from upper
catchment
Channel flow and
overland flooding
in City
Exposed assets and
their vulnerability
and the flood depths.

6. Model workflow
6
Hydrological -
Rainfall-runoff
from upper
catchment
Hydraulic -
Channel flow and
overland flooding
in City
Impact-
Exposed assets and
their vulnerability
and the flood depths.

7. Flooding in the Msimbazi
River
7
• Runoff + sediment from upper catchment
/ Peri-urban area.
• Solidwaste in the channels
• Reduced/insufficient conveyance capacity
of channel and bridges in middle and
lower Msimbazi.
• Sedimentation in the lower Msimbazi
reducing drainage to sea.
• Encroachment on the flood plain
increasing exposure to flooding impacts.

8. Msimbazi River
8
• Hydrological
Model
• Simple 1D2D
modelling
• Unvalidated flood
maps.
1. Problem
Analysis
• Improved
Hydrological
Model
• Improved 1D2D
modelling
• Validated flood
maps.
2. Problem
Analysis • Stakeholder
planning
• Identify solutions.
• Test solutions.
• Evaluate the
solutions.
3. Testing
possible solutions
• Detailed hydraulic
and morphology
model.
• Eng. design + Cost
estimate.
• EIA + RAP
4. Feasibility
Study
5. Construction
10 year process
“Pre-feasibility” “Feasibility” “Implementation”
WB invests heavily in
data collection
WB + GIZ
commission
studies.
WB + GoT
commissions
FS and DD.
World Bank + GoT
agree loan deal.

9. 9
Lower Msimbazi Upgrade Project
World Bank loan for
redesign and
construction of new
elevated bridges, new
housing, improved
drainage and urban park.
Now reaching
construction phase.
10 years of planning,
consultations, designs
and modelling.
Collaboration of:
• CDR International
• VE-R
• Deltares
https://documents1.worldbank.org/curated/en/842751555397752385/pdf/Executive-Summary.pdf

10. The FloodAdapt story
From hazard, to risk to solution testing in Charleston, USA.

11. Many tools enable visualization of
climate risks, but there is a need
for a tool to evaluate solutions
• How does the system respond to
measures?
• What are the most cost effective
measures?
11

12. FloodAdapt Research and development collaboration
12

13. FloodAdapt

14. FloodAdapt

15. FloodAdapt

16. FloodAdapt

17. FloodAdapt
Delft-FIAT:
Fast object-level flood
impact model
SFINCS:
Fast 2D hydraulic
compound flood model

18. FloodAdapt
Delft-FIAT:
Fast object-level flood
impact model
SFINCS:
Fast physics-based
compound flood model

19. Hazard model: SFINCS
Super-Fast INundation of CoastS
19
• Reduced complexity model to compute
compound flooding
• Subgrid approach for high-resolution with speed
• Run time (on i5 laptop) for 6-day simulation: 15
seconds! => potential to assess uncertainties and
risks

20. Damage model: Delft-FIAT
Flood Impact Assessment Tool
20
Session D9: International Session on Flood Modeling
(tomorrow, May 10 - 10:30AM-noon)
A Fast and Flexible Framework for Flood Damage Assessments

21. 21

22. 22

23. Before measure After measure
Elevated homes
means flooding is
not causing
damage
Flooded roads
will isolate this
neighborhood
Damages
Flooded roads
will isolate this
neighborhood

24. The Climate Stress Test story
How much climate change is too much?

25. Climate Stress Testing
Toolbox
Global, Open-source Platform for
Rapid Bottom-up Climate Risk
Assessment

26. 26
Mainstream approach to climate risk assessment:
Predict-then-act
GHG Emission Scenarios
General Circulation
Models (GCMs)
Simulated
impacts
What can happen under climate projections?
Hydrology/system models

27. 28
1. Generate many weather series to
explore natural variability & climate
change (weather generator)
2. Simulate hydrological response to
those weather conditions (wflow)
3. Reveal conditions leading
vulnerabilities – conditions causing
problems based on critical thresholds
4. Assess the plausibility of
vulnerabilities using climate-
information
Weather
Generator
1
Climate stress testing:

28. 29
1. Generate many weather series to
explore natural variability & climate
change (weather generator)
2. Simulate catchment hydrological
response to those weather conditions
(wflow)
3. Reveal conditions leading
vulnerabilities – conditions causing
problems based on critical thresholds
4. Assess the plausibility of
vulnerabilities using climate-
information
Weather
Generator
Hydrological model
(wflow)
1
2
Climate stress testing:

29. 30
1. Generate many weather series to
explore natural variability & climate
change (weather generator)
2. Simulate hydrological response to
those weather conditions (wflow)
3. Reveal conditions leading to
vulnerabilities – conditions causing
problems based on critical thresholds
4. Assess the plausibility of
vulnerabilities using climate-
information
Weather
Generator
Hydrological model
(wflow)
1
2
3
Climate
response
surface
Climate stress testing:

30. 31
1. Generate many weather series to
explore natural variability & climate
change (weather generator)
2. Simulate hydrological response to
those weather conditions (wflow)
3. Reveal conditions leading
vulnerabilities – conditions causing
problems based on critical thresholds
4. Assess climate-informed risks using
GCM projections (or other information)
Weather
Generator
Hydro model
(wflow)
1
2
3
Climate
response
surface
Gcm
Projections
Climate stress testing:
4
+

31. 32
32
1
Create project
Browse existing/on-
going projects
2
Define location
Set basin boundaries,
points of interests

32. 33
1
Create project
Browse existing/on-
going projects
2
Define location
Set basin boundaries,
points of interests
3
Set hydro model
Choose climate
forcing, output vars.
4
Check model fit
Compare simulated to
observed discharge

33. 34
View climate-
informed risks
Assess vulnerability
GCM-informed
likelihood
1
Create project
Browse existing/on-
going projects
2
Define location
Set basin boundaries,
points of interests
3
Set hydro model
Choose climate
forcing, output vars.
4
Check model fit
Compare simulated to
observed discharge
5
Setup climate
stress test
Decide on climate
perturbations
6

34. 35
HydroMT
Model builder interface
deltares.github.io/hydromt
Multigrid
Weather Generator
github.com/Deltares/Wflow.jl
wflow
Distributed hydrological
model
github.com/Deltares/weathergenr
Underlying
modeling
tools

35. Local
Setup
36

36. Thank you