Monitoring the impact of works to improve conditions for navigation on the Danube between Calarasi and Braila, km 375 and km175 (Romania)
Large-scale model Project Cordinator INCDPM Bucharest, Thursday 13 July 2017
Background
• “Monitoring Project” of the environmental impact of the work of the project "Improvement of navigation on the Danube between Calarasi and Braila (km 375 km 175). great deal of monitoring. • Requires a numerical modelling of the local as well as the large-scale phenomenon Deltares Input • Project composition: • INCDPM (lead) • Deltares (sub-consultant) • … others
Teamwork Koen
Mohamed
Ymkje
Erik
Anke Aukje
Amgad
Rolien
Robin Dorothea
Our colleagues from INCDPM & BOKU River Flow 2016
Mohamed F.M. Yossef
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Introduction
The Danube: ▪ Second longest river in Europe: 2783.4 km, with 2414 km suitable for navigation ▪ Romanian Danube: 1075 km, from entry at Baziaş to the mouth at Sulina
Danube – Black Sea canal
River Flow 2016
Mohamed F.M. Yossef
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Introduction Borcea
Bala bifurcation
Bala Old Danube
▪ ▪ ▪ ▪
Navigation depth in the Old Danube is reducing thus causing problems for navigation Repeated dredging (large volumes) detour to the Danube-black sea canal is 110 km Danube – Black Sea canal over 1 million m³/yr of dredging is carried out River Flow 2016
Mohamed F.M. Yossef
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Introduction
▪
Protected Species
▪
According to the IUCN Red List of Threatened Species, over 85% of sturgeon species are classified as at risk of extinction. Romania and Bulgaria are home to the only viable wild sturgeon populations left in the European Union. Six species of sturgeons were once native to the Danube River Basin, only four still reproduce in the lower Danube.
▪
▪
River Flow 2016
Mohamed F.M. Yossef
8/25/2017
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The problem @ the Bala bifurcation Historical situation: Borcea
Bala Old Danube
%discharge into the Danube
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Data: water levels, discharges at some stations QCernavoda
HCernavoda
QSilistra
HSilistra Relation QCernavoda/ QSilistra, solid line gives an impression of the a decreasing trend over years. 25 August 2017
Data: discharge distribution Lalomita system The Bala is taking over
The Danube is closing off
25 August 2017
Bala bifurcation Studies over decades are motivated by the wish to improve the Danube navigability
Bala Bifurcation
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Proposed intervention – sill Borcea
Bala Old Danube
structural measures planned to “correct” the discharge distribution in order to improve navigability Submerged sill: Phase 3 sill
Danube – Black Sea canal crest level: 0.22 m MNS 8/25/2017
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The function of the sill – large scale picture
A Borcea
Bifurcation Bala-Old Danube
Confluence Vadu Oii
Danube
Before construction of the Sill
B
B
After construction of the Sill – for the same discharge
A+
A
Danube sill
Borcea B
Medium-scale
Large-scale model
B
Monitor the function – supported by models
Fish AND ships NOT
Improve navigation without impacting fish
Fish OR ships
?
River Flow 2016
Mohamed F.M. Yossef
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the question to solve
Will the sill help navigation and will it influence sturgeon migration?
Possible impact on fish migration Detailed 3D velocity patterns in the vicinity of the sill
Functioning of the sill Discharge distribution Velocities Water levels Long-term influence on the development of the river bed (is the sill a sustainable measure?)
Local hydrodynamic model & Large-scale morphodynamic model
River Flow 2016
Mohamed F.M. Yossef
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Overview of the models ▪
detailed hydrodynamic model of the bifurcation area (3D) ➢ flow patterns around the structure
▪
coarser model morphydynamic of the bifurcation area (2D) ➢ local effect of alternative measures
River Flow 2016
Mohamed F.M. Yossef
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Overview of the models ▪
large-scale morphodynamic model (quasi-3D) ➢ long-term effect of the sill for navigation ➢ discharge distribution, development of river bed (How sustainable is the measure?)
River Flow 2016
Mohamed F.M. Yossef
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Large-scale model ▪ ▪
▪
aim: evaluate in how far the bottom sill improves navigation conditions on the long-term quasi-3D model: 2D + secondary flow model which includes parameterisation of the vertical velocity profile (spiral flow motion) 50 years autonomous & Comparative analysis
River Flow 2016
Mohamed F.M. Yossef
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Delft3D suite Delft3D
A proven track record Open source
Example: Model of the Rhine Branches in the Netherlands
Danube large-scale model
Danube
Danube large-scale model
Project area
Danube large-scale model
Today’s presentation
Model construction – land boundaries
Land boundaries (collected by INCDPM) define model extent, main channel, floodplains
Model construction – vegetation
vegetation coverage: Corine land cover data define floodplain roughness
forest
river
wetlands
Model construction – bed levels Measurements
Online data sets
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Model construction – bed levels River bed level multiple surveys by INCDPM flood plain elevations global data sets
Calibration Objective of calibration: • Reproduce discharge distribution between branches Primary focus • reproduce observed water levels
approach: • Adjust roughness of river bed
• calibrate for several discharge levels: 4000, 6000, 8000 and 11000m³/s at Silistra Automated calibration using OpenDA OpenDA is open source www.openda.org
Large-scale model – calibration hydrodynamics ▪
hydrodynamic calibration: water levels and discharge distribution
gauging stations used for calibration
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Large-scale model – calibration hydrodynamics Q(Silistra) = 4.000m³/s
Q(Silistra) = 6.000m³/s
Q(Silistra) = 8.000m³/s
Q(Silistra) = 11.000m³/s
Running long simulations: discharge schematisation 16000
14000
12000
4
Q (m3/s)
10000
8000
6000
4000
2000
0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035
1
Date
4 2
3
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Discharge schematisation 16000 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2002 2003 2004 2005 2006 2007 2008 2009 2011
14000
12000
discharge [m3/s]
10000
moved hydrograph times to match peaks
16000 8000
14000 12000 6000
10000
8000 4000 6000
4000 2000
2000
0
0
0
100
0
50
200
100
300
400
150
200 days in year [days]
500
250
600
700
300
350
800
400
matched hydrograph peaks 16000 14000 12000 10000 8000 6000 4000 2000 0
8/25/2017 0
100
200
300
30 400
500
600
700
800
Discharge schematisation
Number of days
Schematic hydrograph detailed curve schematised curve discharge classes
14000
discharge (m3/s)
12000
10000
8000
6000
4000
2000 0
0.1
0.2
0.3 0.4 0.5 0.6 0.7 0.8 percentage of time equaled or exceeded
0.9
1
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Running long simulations: quasi-steady & accelerated • Repeat a yearly schematised hydrograph using a sequence of steady discharges • Apply a “morphological acceelration factor” to speed up morphology (same morphological changes in shorter flow period): factor 50 – 200 8000
8000
Q2
7000
7000
3 (m /s)
Q3
4000
5000 4000
Q
Q (m3/s)
Q1
5000
6000
morfac
6000
3000
3000
2000
2000
1000
1000
0 1993
1994
0 1993
1995
Mohamed F.M. Yossef
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1995 Time
Time
River Flow 2016
1994 1996
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1996
Running long simulations: Simulation Management Tool Operated using Python scripts
database
restart file Q1
restart file Q2
Q3
hydrodynamic parameters
morphodynamic parameters River Flow 2016
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ETCETERA
restart file
50 years of morphological developments
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Results: sediment transport ▪ ▪
morphodynamic calibration on development of selected sand bar, sediment transport rate very little data available total transport rate at Chiciu-Calarasi (kg/s)
reported annual mean transport load
River Flow 2016
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Results: sediment transport ▪ ▪
morphodynamic calibration on development of selected sand bar, sediment transport rate very little data available total transport rate at Chiciu-Calarasi (kg/s)
reported annual mean transport load
River Flow 2016
Mohamed F.M. Yossef
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Large-scale behaviour – Autonomous behaviour Reference 2011: Autonomous behaviour +50 years
Average: – 0.6 cm/year
Average: +1.0 cm/year
Blue = Erosion Red = Deposition
after Q = 4000 m3/s
after Q = 11000 m3/s
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Large-scale behaviour – Autonomous behaviour Reference 2011: Autonomous behaviour +50 years
Change in water level
Change in flow depth 8/25/2017
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Results: bed levels ▪
long-term effect of the sill on bed levels
change in bed level after 50 years, without
sill
Aggradation upto +2m locally On Avearge 1 cm/yr
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change in bed level after 50 years, with
sill
Aggradation upto +1m locally on avearge 0.5 cm/yr
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Results: bed levels ▪
long-term effect of the sill on bed levels
change in bed level after 50 years, without sill
Aggradation upto +2m locally On Avearge 1 cm/yr
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Relative change in bed level in 50 years, with sill, compared to situation without sill
Bed level relatively upto +1m higher with sill
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Results: navigation depth ▪
long-term effect of the sill on water depths
change in water depth in 50 years, without sill
reduction of water depth up to 2m locally
River Flow 2016
Mohamed F.M. Yossef
relative change in water depth in 50 years, with sill, compared to situation without sill
water depths relative increase upto 1m higher with sill 8/25/2017
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Conclusions ▪ We run the model for 50 years; the simulations were extended for a long period to evaluate the long-term effects. ▪ The morphological developments are slow. The rate of change is in the order of a few centimetres per year (± 1 cm/year); not easy to detect from short-term measurements. ▪ From the analysis of autonomous behavior, ▪ The observed trend of decreasing discharge of the LOD will most likely continue. ▪ the LOD exhibits a general tendency for bed aggradation and the Lower Borcea shows a tendency for bed level degradation. ▪ The changes, though large in the long term, they are rather small on a yearly basis. ▪ The discharge distribution at the Bala bifurcation is not stable; the discharge into the LOD decreases in time.
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Conclusions ▪ Regarding the effect of the sill; ▪ The introduction of a sill causes a small reduction in the aggradation trend of the LOD and the Lower Borcea becomes relatively more stable ▪ The effect of the sill on bed levels is relatively small. ▪ With respect to the discharge distribution, though the sill may be considered relatively small, it seems that it creates a stabilising effect. ▪ The bifurcation is still not stable, as the discharge into the Lower Old Danube still decreases with time. ▪ The effect of the sill is rather slow & not sufficient to solve the navigation problem
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Thank you
Project Cordinator INCDPM
Delft3D Open Source Community www.oss.deltares.nl
[email protected]
