Presentation by Olivier Barbet, ISL Ingénierie, France, and Eelco Verschelling, Deltares, The Netherlands, at the Delft3D - User Days (Day 1: Hydrology and hydrodynamics), during Delft Software Days - Edition 2019. Monday, 11 November 2019, Delft.

1. Cliquez et modifiez le titre
Hydrodynamic modelling
of Inner Niger Delta (DIN)
Olivier Barbet (ISL)
Eelco Verschelling (Deltares)
Niger Basin
Authority
(ABN)

2. •Specify and quantify the wetland ecosystem and socio-agro-
economic services provided by the annual flooding of the Inner
Niger Delta (DIN) in Mali
•Provide ABN (Niger Basin Authority) and the governments of
Mali and Guinea with all the indicators that will enable them to
decide on development choices to implement in the Niger
Basin
•Provide NBA with a modeling tool able to simulate different
development scenarios
2
Project objectives

3. Today, a not recommended area ➔
Dependency on open data and very old local
data
One of the first consultancy projects
with the new lateral 1D2D coupling in
Delft3D FM Suite
3
Interesting and Challenging project

4. Inner Niger Delta
(DIN area)
4
Niger Basin
~ 4 200 km (5 countries)
~ 2,2 Mkm² (9 countries)

5. Faguibine
Lac Takara
Lac Kamango
Lac Gouber
Lac Télé
Lac Fati
Lac Horo
Lac Aougoundou
Lac Niangaye
Lac Do
Lac Garou
Lac Haribonga
Lac Korarou
Lacs Debo et
Walado
Lac Korientzé
Yearly Inundation area: 36 000 km²
Around 400km in length
Total area : 250 000 km²
Lac Takadji
Lac Tanda
Lac Kabara
5
Inner Niger Delta

6. Fomi dam
(planned)
Large irrigation area
(Office du Niger)
Selingue dam
6
Impact of upstream projects on DIN stakeholders?

7. MIKE-BASIN model of
Upper Niger basin
Delft3D FM 1D2D
MODEL OF DIN area
IMPACT ASSESSMENT
MODELS / ECOSYSTEM
SERVICES MODELS
Modelling tools
7

8. MIKE-BASIN model of
Upper Niger basin
Delft3D FM 1D2D
MODEL OF DIN area
IMPACT ASSESSMENT
MODELS / ECOSYSTEM
SERVICES MODELS
Modelling tools – this presentation
8

9. 9
Field information
Structure of hydrodynamic model
Modelisation area
Representation in the model
=> Rivers in 1D
=> Inundation area in 2D

10. 10
Construction – basic data
• 1D stream network : open access EO images (Landsat – 8)
• river geometry : (very old ~1980) surveyed cross sections in paper
format
• 2D surface levels: open access DEM/DTMs (SRTM/MERIT)
• limited information on secondary networks and hydraulic structures
Structure of hydrodynamic model

11. 11
Construction – basic data
illustration - 1D streams - method: GIS
Structure of hydrodynamic model
Digitalization of network from Landsat 8 images
➔ 99 polylines on the study area
➔ Good correspondance with MERIT DEM

12. 12
Construction – flexible mesh
Structure of hydrodynamic model
Cut river from 2d grid to
prevent double counting
Lateral
1d2d links
Finer gridcells
closer to the river
Mopti : confluence Niger / Bani

13. 13
Forcing
Structure of hydrodynamic model
Rating curve at
Taoussa
Direct Precipitation & PET on the grid
(source: Earth2Observe / open access )
Inflows (MIKE-BASIN
& OBSERVED)

14. 14
Calibration data used
- Levels and rating curves at a limited number of gauging stations
- Inundation patterns derived from Satellite Images (MODIS) using
appropriate water indices (MNDWI / NDMI1)
Model calibration
1 (Modified) Normalised Difference Water Index

15. 15
- Model ready
- Currently running climate scenarios and strategies
- Providing the results (inundation areas, durations, heights,…) for the socio-
agro-economic services model
- Preparation for the training of NBA’s experts
Current status

16. Some lessons learned
• 1D2D link works well
• Much easier to combine different resolutions compared
to SOBEK 1D2D (nested grids…)
• Lot of work needed to align MERIT DEM with local data
• Calibration results were surprisingly well, given state of
data
• Year-round wetland modelling using Delft3D FM 1D2D
could benefit from inclusion of simple groundwater
model to model infiltration & exfiltration
Interesting aspects & Challenges:
• One of first consultancy projects
with 1D2D coupling in Delft3D FM
• Dependency on open data and
old local data

17. Thank you!
Questions?