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Solution to the Breach of the Dike of Keur Bara KAIRE, Located in the Commune of Notto Diobasse in the Department of Thiès, Senegal

Ndiouga Camara*,  Birane Niane,  Séni Tamba
Published in Journal of Civil, Construction and Environmental Engineering (Volume 9, Issue 6)
Received: 16 July 2024     Accepted: 22 August 2024     Published: 28 November 2024
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Abstract

This article studies the rupture of the Keur Bara KAIRE dike, located in the commune of Notto Diobasse in the department of Thiès in Senegal. The village is crossed by a stream which collects rainwater from the west to the east, following a natural slope. The overflow of this stream causes serious flooding, leading to the total cutting of the road and the isolation of the population. These floods had tragic consequences, resulting in two losses of human life. To regulate the water level, prevent flooding and protect agricultural and urban areas from overflows, the Senegalese authorities initiated the project to build the Keur Bara KAIRE dike in 2004, unfortunately the latter gave way in 2017. The geotechnical analysis was carried out on samples taken from various points on the site, revealing that the terrain is mainly composed of fine sand and the embankment is made with clayey sand. Morphometric and hydrological investigations highlight that the watershed of the Keur Bara KAIRE dike covers an area of 3.72 km², with a projected flow of 54.99 m³/s. The resizing of the dike revealed the following data: a length of 132 meters and a height of 3 meters. The spillway is 52.99 meters long with a reservoir height of 1.22 meters. The bay walls have a thickness of 50 cm and the embankments have a slope of ½ upstream and downstream. The stability calculation on the broken dike reveals a sliding safety factor (FSG) of 1.84 which complies with the standard and an overturning safety factor (FSR) of 0.13 which is not verified. The surface of the watershed which is equal to 3.72 km², also the smallest height of precipitation is equal to 234.9 mm and the largest 664.4 mm, the ORSTOM and CIEH methods for hydraulic calculations.

Published in Journal of Civil, Construction and Environmental Engineering (Volume 9, Issue 6)
DOI 10.11648/j.jccee.20240906.13
Page(s) 197-210
Creative Commons

This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.

Copyright

Copyright © The Author(s), 2024. Published by Science Publishing Group
Previous article
Keywords

Keur Bara KAIRE, Dike, Geotechnical, Topography Surveys, Watershed, Stability

1. Introduction
The frequency and intensity of floods have increased in recent decades, largely due to climate change and increasing urbanization
[1]
. According to the World Food Program (WFP), devastating floods in West and Central Africa have affected five million people in 19 countries in the region. These floods displaced tens of thousands of people from their homes and decimated more than a million hectares of cultivated land
[2]
. Senegal is not left out since the country has experienced recurrent floods since 1989. This can be explained by rapid urbanization. The urbanization rate increased from 23% in 1960 to 38.40% in 1988, 40.6% in 2000 and 45.2% in 2013, thus leading to the creation and proliferation of irregular neighborhoods which represent nearly 40% of the total habitat in Senegal, more than 2/3 of which is located in flood zones
[3]
. Regions like Thiès are particularly affected due to the lawless occupation and topography. It is crucial to understand that flooding varies by region, season and local conditions, and flood responses must be tailored to the specific needs of each region
[4]
. However, huge investments have been made to build community resilience and build infrastructure. Among these infrastructures, there are protective dikes designed to meet specific needs. In Senegal, after the drought cycle of the 1970s, the Senegalese government invested in the construction of dikes which were used to retain water for agriculture and livestock such as the Allou Kagne 2 dam but also dykes which have the role of protecting populations against flooding such as the Keur Bara KAIRE dike which is the subject of this article. Indeed, this village is crossed by a stream which collects rainwater coming from the West to the East, following a natural slope. The passage of these waters causes serious flooding, literally cutting the road and isolating the population, which resulted in two losses of human life. In response to this situation, in 2004 the Senegalese government undertook the construction of the Keur Bara KAIRE dike, a structure intended to control the water level, prevent flooding, and protect agricultural and urban land from overflows. However, this dike failed in 2017, restoring previous problems. A dike rupture can cause a wave of submersion that is much more dangerous than the flood from which it was supposed to protect populations and its causes can be technical, natural or human. The general objective of this article is to contribute to the protection of populations against flooding by trying to propose a solution to make the dike functional
[5]
.
2. Materials and Methods
2.1. Data Acquisition
The study area is located in the department of Notto Diobass, in the Thiès Region of Senegal. Figure 1 shows the location of the area.
Figure 1. Geographical location of the study area on Qgis.
Figure 2 provides an overview of the study area.
Figure ‎2. Delimitation of the study area on Google Earth.
The figure 3 shows the evolution of the demographics of the municipality.
Figure 3. The evolution of the demographics of the municipality.
The figure 4 gives a representation of the evolution of humidity in 2021.
Figure 4. Variation of humidity in the Thiès region
[3].
The figure 5 shows the temperature variation.
Figure 5. Variation of monthly temperature in the Thies region in 2018
[5].
The winds are moderate and their speeds vary from 2 to 14 m/s.
[6]
Rainfall follows a sawtooth pattern (figure 6) with an average of around 471 mm per year.
Figure 6. Variation in the average annual rainfall of Thiès from 1989 to 2019
[1].
Figure 7. Geological section of Thiès
[6]
.
The morphology of the department causes most of the runoff water to converge towards the lowlands. In other words, the waters leave the highest points (altitude 112 m) towards the lowest (altitude 49 m). This makes the study area, located at an altitude of 82 m, a runoff zone
[7]
.
To characterize the geological structure of Thiès, a section of the different layers was made from the logs of several boreholes as illustrated in Figure 7
[6]
.
Figures 8-9-10 and 11 illustrate the current state of the Keur Bara KAIRE dike.
Figure 8. Sandbags stored on the track ditch.
Figure 9. Rows of rocks to reduce wave pressure.
Figure 10. Rupture at the down stream slop.
Figure 11. Rupture at the spillway.
Thus, the data obtained makes it possible to follow the procedures and approaches to deal with this specific problem of the dike.
2.2. Data Processing and Analysis
[8]
Seven (7) boreholes were made with a depth of 1 m:
Three points upstream,
S1 upstream with coordinates 14°43’51.1’’ N / 17°4’3.1’’ W with an altitude of 77m;
S2 upstream with coordinates 14°43’50.2’’ N/ 17°4’2.4’’ W with an altitude of 76m;
S3 upstream with coordinates 14°43’49.6’’ N / 17°4’2.1’’ W with an altitude of 77m.
Three downstream,
S1 downstream with coordinates 14°43’50’’ N / 17°4’4.7’’ W with an altitude of 77m;
S2 downstream with coordinates 14°43’49.2’’ N / 17°4’3.7’’ W with an altitude of 77m;
S3 downstream with coordinates 14°43’48.2’’ N / 17°4’2.9’’ W with an altitude of 77m.
A point at the embankment of the dike with coordinates 14°43’49’’ N / 16°55’57’’ W with an altitude of 77m,
A sample is taken from the protective layer.
An in situ permeability test was carried out to determine the permeability of the soil.
Table 1 gives the permeability classes.
Table 1. Permeability classes depending on the permeability coefficient.

Permeability classes depending on the permeability coefficient

K (m/s)

Degree of permeability

Medium to large gravels

10-1 – 10-3

Very high

Small Gravel, Sand

10-3 – 10-5

Quite high

Very fine Sand, silt sand, lœss

10-5 – 10-7

Weak

Compact silt, clay, loam

10-7 – 10-9

Very weak

Frank clay

10-9 – 10-12

Vitually waterproof
GTR classification is a soil classification method used to evaluate soil properties. The GTR classification is made according to the tables in Figures 2 and 3.
Table 2. GTR class A classification.

Classification according to natur

Classification according to water status

nature parameters First level of classification

Class

nature parameters Second level of classification

Subclass function of nature

Status Settings

State function subclass

Dmax≤50mm and Sieve at 80µm>35%

A

Sols fins

VBS ≤2,5

ou

Ip≤12

A1

Little plastic silts, loess, alluvial silts, little polluted fine sands, little plastic arenas

IPL≤3 ou Wn≥1,25WOPN

A1th

3<IPL≤8 ou 1,10≤Wn<1,25 WOPN

A1h

8<IPL≤25 ou 0,9WOPN≤Wn<1,1WOPN

A1m

0,7WOPN≤Wn<0,9WOPN

A1s

Wn<0,7 WOPN

A1ts

12<Ip≤25

ou

2,5<VBS≤6

A2

Fine clay sands, clay silts and poorly plastic marls, arenas

IPL≤2 ou Ic≤0,9 ou Wn≥1,3WOPN

A2th

2<IPL≤5 ou 0,9≤Ic<1,05 ou 1,1WOPN≤Wn<1,3 WOPN

A2h

5<IPL<15 ou 1,05<Ic≤1,2 ou 0,9WOPN≤Wn<1,1WOPN

A2m

1,2<Ic≤1,4 ou 0,7 WOPN≤Wn<0,9WOPN

A2s

Ic>1,3 ou Wn<0,7WOPN

A2ts

25<Ip≤40

ou

6<VBS≤8

A3

Clays and marly clays, very plastic silts

IPL<1 ou Ic≤0,8 ou Wn≥1,4WOPN

A3th

1<IPL<3 ou 0,8≤Ic<1 ou 1,2WOPN≤Wn<1,4 WOPN

A3h

3<IPL<10 ou 1<Ic≤1,15 ou 0,9WOPN≤Wn<1,2 WOPN

A3m

1,15<Ic≤1,3 ou 0,7 WOPN≤Wn<0,9WOPN

A3s

Ic>1,3 ou Wn<0,7WOPN

A3ts

Ip>40

ou

VBS>8

A4

Very plastic clays and marly clays

Threshold values of state parameters, to be defined in support of a specific study

A4th

A4h

A4m

A4s
Table 3. GTR class B classification.

CLASSIFICATION TO USE FOR EMPLOYMENT CLASSIFICATION TO USE FOR SHAPE LAYERS

CLASSIFICATION ACCORDING TO NATURE

CLASSIFICATION ACCORDING TO WATER STATUS

CLASSIFICATION BY BEHAVIOR

nature parameters First level of classification

Class

nature parameters Second level of classification

Subclass function of nature

Status Settings

State function subclass

behavior settings

Subclass behavior function

Dmax≤50mm

et

Sieve at 80µm≤35%

B

Sols sableux et argileux avec fines

Sieve at 80µm≤12%

Sieve at 2mm>70%0, 1≤VBS≤0,2

B1

silite sands

Materials generally insensitive to water

FS≤60

FS>60

B11

B12

Sieve at 80µm≤12%

Sieve at 2mm>70%

VBS>0,2

B2

Clayey sands (lightly clayey)

IPL≤4 ou Wn≥1, 25WOPN

B2 th

FS≤60

B21 th

FS>60

B22 th

4<IPL≤8 ou 1,10≤Wn<1, 25 WOPN

B2 h

FS≤60

B21 h

FS>60

B22 h

0,9WOPN≤Wn<1, 10WOPN

B2 m

FS≤60

B21 m

FS>60

B22 m

0,5WOPN≤Wn<0, 9WOPN

B2 s

FS≤60

B21 s

FS>60

B22 s

Wn<0,5WOPN

B2 ts

FS≤60

B21 ts

FS>60

B22 ts

Sieve at 80µm≤12%

Sieve at 2mm>70%0, 1≤VBS≤0,2

B3

Silty gravel

Materials generally insensitive to water

LA≤45 et

MIDE≤45

B31

LA>45 et

MIDE>45

B32
For watersheds, their characteristics can vary depending on different factors, such as geology, topography, vegetation, climate and land use
[9]
. Figure 12 represents the zoning done on Google Earth imported onto Global Mapper.
Figure 12. Zoning for watershed delimitation on Google Earth pro.
The design flood calculation is done using the Grésillon formula which allows you to go from the ten-year flood to the hundred-year flood as given in formula 1:
Q100=C* Q10(1)
Q10: Centennial flow;
C: increase coefficient given by the Gradex method (formula 2):
C=1+P100-P10P10*Tb240,12Kr10(2)
P10: daily precipitation corresponding to a return period of 10 years;
P100: daily precipitation corresponding to a return period of 100 years;
Tb: basic time (in hours);
Kr10: runoff coefficient of the ten-year flood (expressed as a fraction).
For the ratio between centennial and ten-year frequency precipitation:
P100-P10P10=0,45 in the sahelian zone0,38 tropical area
Losses occur through infiltration and evaporation. The methodology adopted for data analysis made it possible to know the shape of the dike, the nature of the soil and to verify the stability of the dik
[10]
.
3. Results and Discussions
The Keur Bara KAIRE watershed is delimited using Global Mapper software. Figure 13 gives the delimitation of the sub-watersheds.
Figure 13. Demarcation of the sub-watersheds of Keur Bara KAIRE on Global Mapper.
Figure 14 gives the hypsometric curve of the Keur Bara KAIRE watershed.
Figure 14. Hypsometric curve of the Keur Bara KAIRE watershed.
The hypsometric curve made it possible to determine the altitudes at 5% and 95% of cumulative surfaces which are respectively equal to 99.2 m and 84 m. These altitudes made it possible to calculate the overall slope index. Table 4 presents the characteristics of the Keur Bara KAIRE watershed.
Table 4. Characteristics of the Keur Bara KAIRE watershed
[8]
.

Watershed characteristics

Results obtained

Area S in km²

3,72

Perimeter P in km

10,43

Maximum altitude in m

104

Minimum altitude in m

82

Hydraulic length in km

2,54

Average slope

0,63

Shape index KG

1,52

Length of the equivalent rectangle L in km

4,37

Overall slope index Ig in m/km

5,98

Specific height difference Ds in m

11,54

Basin typology

Very small watershed

Relief typology

Weak
These results show that the basin is very small with an elongated shape and low relief.
The average permeability coefficient (km) is equal to 3.66731.10-6, so the permeability of the soil is low.
The particle size curves in Figure 15 represent the results of the particle size test carried out on the seven (7) samples.
Figure 15. Particle size curves on the seven (7) samples.
The particle size curves do not allow a good classification of the soil due to the absence of the parameters D10, D30 and D60. It was therefore necessary to carry out the particle size test by sedimentometry. The results of the Cc and Cu calculations are presented in Table 5.
Table 5. Curvature and uniformity coefficients.

Samples

Curvature coefficient (Cc)

Uniformity coefficient (Cu)

Upstream S1

4,20

6,20

Upstream S2

6,30

10,17

Upstream S3

4,65

8,33

Downstream S1

0,39

4,62

Downstream S2

0,55

4,88

Downstream S3

0,39

4,62

Embankment of the dike

1,15

4,62
The uniformity coefficients of all samples are greater than 2, so the grain size of the soil is spread out. The curvature coefficients of the upstream and downstream samples are not between 1 and 3, so the soil is poorly graded upstream and downstream of the dike. On the other hand, the coefficient of curvature of the dike backfill sample is between 1 and 2 so the grain size of the dike backfill is well graded.
The results of the tests on the specific weight are given in table 6.
Table 6. Results of specific weights of solid grains.

Samples

γs moyen (g/ml)

Upstream S3

2,649

Downstream S1

2,622

Downstream S2

2,927

Downstream S3

2,653

Embankment of the dike

2,613
Average γs is greater than 2.6 g/ml so the soil contains heavy particles. The results of the methylene blue tests are presented in Table 7.
Table 7. Results of the methylene blue test.

Samples

VBS

Upstream S3

1,12

Downstream S1

0,71

Downstream S2

0,71

Downstream S3

0,56

Embankment of the dike

0,81
The VBS values are in the interval [0.2; 1.5] therefore the soil is sandy-loamy.
The results of the sand equivalent test carried out on samples S3 upstream, S1, S2 and S3 downstream as well as on the support soil of the dike are recorded in table 8.
Table 8. Sand equivalent results.

Samples

Sand equivalent

Upstream S3

27,07

Downstream S1

27,06

Downstream S2

42,27

Downstream S3

42,21

Embankment of the dike

53,45
The sand equivalents are less than 60 so the soil is clayey sand. The Atterberg limits test is carried out on the upstream samples S1 and S2. Figures 16 and 17 represent the curves for determining the liquidity limit.
Figure 16. Curve of the liquidity limit of the upstream S1 sample.
Figure 17. Curve of the liquidity limit of the upstream S2 sample.
Figures 16 and 17 give the values of the liquidity limit of upstream S1 and upstream S2 which are respectively 43.5% and 41.6%. The results of the compactness index (Ic) and the plasticity index (Ip) are presented in Table 9.
Table 9. Atterberg limit results.

Samples

Hint

Upstream S1

Ip

17,8

Ic

2,21

Upstream S2

Ip

25,6

Ic

1,38
The Ip are the interval [15; 40] and the Ic > 1 therefore the soil is in a plastic and solid state.
The GTR classification was made using the results obtained in the geotechnical tests.
Samples S3 upstream, S1, S2 and S3 downstream of the dike are class A1, so they are lightly polluted fine sand. On the other hand, samples S1, S3 upstream are respectively fine clayey sand and marly clay. This can be explained by the fact that runoff water carries materials with it. The embankment is class B2 so the soil is a slightly clayey sand.
To check the stability of the structure, it is necessary to know the cohesion and the internal friction angle of the dike backfill. Table 10 gives the normal and tangential stresses at the different loadings.
Table 10. Results of calculations of σn (kPa) and τ (kPa).

Overload (kg)

σn (kPa)

τ (kPa)

4

237,819

87,582

8

514,370

305,999

16

1023,195

282,611
Figure 18 shows the shear stress-deformation curve plotted using Table 10.
Figure 18. Shear force-strain curve.
The cohesion and friction angle are given in table 11.
Table 11. Cohesion and angle of internal friction.

Cohesion

C(kPa)

0

Internal friction angle

φ (°)

21,82
The cohesion is zero, which confirms that the backfill is made with sand.
Figures 19 and 20 respectively give the variation in the moving average of annual rainfall and the variation in the moving average of daily maximum rainfall.
Figure 19. Variation in the moving average of annual rainfall.
Figure 20. Variation in the moving average of daily maximum rainfall.
The analysis of this data did not show any doubtful periods. Therefore, these data will be used for the diagnosis of the dimensioning of the work.
The graphic adjustment of the daily maximum data by Gumbel’s law made it possible to obtain the graph in Figure 21.
Figure 21. Graphical adjustment of daily maximum rainfall.
The analysis of Figure 21 reveals that there is a distribution of the cloud of points around the adjustment line. Thus the results of the parameters obtained by the graphical method will be used as input parameters for the design of the structure. Table 12 gives the values of Gumbel's law (s and X0) obtained by the graphical method.
Table 12. Gumbel Settings by Graphical Adjustment.

δ (écart type)

a

moyenne

X0

s

65,841

0,019

200,906

171,274

51,356
The results obtained by the moment method are reported in Table 13.
Table 13. Gumbel Parameters by Adjustment by the Moment Method.

δ (écart type)

moyenne

s

X0

65,841

200,906

51,356

171,274
The scale factor and the amount of rainfall in the current state are the same in both methods.
For the estimation of the flow by the ORSTOM method, since the area of the catchment area is 3.72 km² also the smallest height of precipitation is equal to 234.9 mm and the largest 664.4 mm, so all heights are in the interval [150; 1600]. The decadal flow calculations by the ORSTOM method are given in Table 14.
Table 14. Calculation of Qr10 by the ORSTOM method.

A

0,91

P10

286,844

P100

407,521

Kr10

24

Pan

441,24

S

3,72

α10

2,6

Tb10

440

Qr10 (m3/s)

23,17
For the ORSTOM method, the ten-year flood amounts to 23.17 m3/s.
For the estimation of the flow by the CIEH method, since the catchment area is 3.72 km² so it is in the range [0.07; 2,500] also the smallest height is equal to 234.9 mm and the largest 664.4 mm, so all heights are in the interval [150; 1600]. The results of the calculations are recorded in Table 15.
Table 15. Calculation of Q10 by the CIEH method.

Pan

441,24

S

3,72

Ig

5,98

Q10 (m3/s)

13,86
For the CIEH method, the ten-year flood is equal to 13.86m3/s.
Table 16 presents the results of the centennial flow calculation or project flood.
Table 16. Project Flood Calculation.

Q10 (m3/s)

C

Q100 (m3/s)

ORSTOM

23,17

2,37

54,99

CIEH

13,86

32,89
For safety reasons, the maximum ten-year flood Q100 = 54.99 m3/s is used as the project flow.
To make the diagnosis of the dike, it is necessary to compare the dimensions found on site with the results of the resizing. Tables 17 and 18 show the dimensions of the dike found at the site and the results of the dike resizing, respectively.
Table 17. Dimensions of the dike.

Ridge width Lc (m)

7,02

Width of the base of the dike Lb (m)

58,8

Height of the dike H (m)

2,88

Water Slide h (m)

0,7

Height of the reservoir Hr (m)

2,27

Length of weir (m)

30,00
Table 18. Resizing the dike.

Wind speed (u in km/h)

15,24

TN Rating (m)

75,06

Lengths of the (m)

132

FETCH Length (Lf in m)

0,12

Wave height (Hv in m)

0,79

Wave propagation speed ( v in m/s)

3,09

Revenge (R in m)

1,08

Height of the dike (Hd in m)

3,00

Ridge width (Lc in m)

2,86

Width of the base of the dike (Lb in m)

14,86

Water Gap (h in m)

0,70

Height of the reservoir (Hr in m)

1,22

Flow coefficient (m)

0,40

Project flood (Q in m3/s)

54,99

Spillway length (L in m)

52,99
The resizing showed that the dimensions of the dike are acceptable except for the length of the spillway. The calculation results for the LANE rule check are shown in Table 19.
Table 19. Checking for infiltration under the dike.

Lv (m)

LH (m)

C

Hr (m)

LV+13*LH≥C*Hr

58,81

132

7

1,22

vérifié
The LANE rule is respected, so the risk of infiltration under the dike is eliminated.
The results for the protection of the upstream slope are given in Table 20.
Table 20. Calculation of the thickness of the upstream slope protection.

Y

Pente

C

V (m/s)

e (m)

2,8

1/2

0,026

3,09

0,24
For good protection of the upstream slope, the thickness of the protective layer had to be equal to 24 cm, but the protective layer found on the site is 15 cm. So the protection of the upstream slope is not good. The protection of the downstream embankment is made of perré with a thickness of 20 cm, which complies with the standard which requires a thickness of at least 16 cm, so it is acceptable. The ridge protection is made of laterite with a thickness of 16 cm, which is below the standard. The thickness of the laterite layer should be at least 20 cm. So the protection of the ridge is not good.
The results of the slip stability calculations are given in Table 21.
Table 21. Calculation of Slip Stability.

W1

U

Pa

FSG

179,69

205,8

2,45

1,84
FSG=1,84≥1,5 Slip stability is checked.
The results of the rollover stability calculations are given in Table 22.
Table 22. Calculation of Rollover Stability.

∑M Stabilizers

530,39

∑M Stunning

4035,53

FSR

0,13
FSR=0,13<1,5 Rollover stability is not checked.
In summary, the diagnosis of the dike failure according to the three hypotheses raised yielded:
3.1. Excess Flooding
Taking the average annual precipitation of 1989 (609.9 mm), which returns ten years later in 1999 (618.5 mm), as a reference point, the rupture may be due to an excess of flooding since in 2010, the average rainfall was well above the reference threshold, reaching 664.4 mm. So the rupture may be due to an excess of flooding.
3.2. External Erosion
To minimize the risk of breakage, good slope protection is necessary. However, the protection of the upstream slope, which was supposed to be 24 cm thick, is 15 cm. Similarly, the thickness of the laterite layer of the ridge which must have been 20 cm is 16 cm. So the protections at the crest and the upstream embankment are not good. If slope protection is not adequate, water can seep into the embankment, which can cause erosion. In this context, it is relevant to speak of external erosion, since the protection of the downstream slope is sufficient.
3.3. Undersizing
The sizing is acceptable except for the length of the spillway. Also, the overturning stability is not checked, which can be a cause of breakage.
4. Conclusion
There are many shortcomings in the design of the Keur Bara KAIRE dike. First there is the excess flooding, then the poor protection of the embankments and finally the undersizing. This confirms the hypotheses outlined above. Therefore, to solve the flooding problems caused by the failure of the dike, it is first proposed to redo the structure using a homogeneous earthen dike with zones with a slope of 1/2 upstream and downstream, clay sand for the backfill to prevent water infiltration, a protective layer of 24 cm for the upstream embankment, 20 cm for the crest and 15 cm for the downstream embankment and for more resistance, build 50 cm thick ramming walls with a length of 1 m for the anti-fox screen. Table 23 presents the results of the design of the flanking walls.
Table 23. Dimensioning of the flanking walls.

Peak Width (m)

2,86

Height of the wall above the TN (m)

3

Wall thickness (m)

0,5

Length of the anti-fox screen (m)

1

Slope of side walls

1/2 (Upstream and downstream)
It is essential to consider that this article is not limited to the simple rehabilitation of the dike.
In order to guarantee the sustainability of the structure, it would be wise for the stakeholders to work together to develop an organizational plan dedicated to monitoring, control and maintenance. This will establish a solid structure that will ensure the long-term preservation of the structure.
Abbreviations

°C

Degree Celsius

ANACIM

National Agency for Civil Aviation and Meteorology

ANSD

National Agency for Statics and Demography

Cc

Curvature Coefficient

CIEH

Inter-African Committee for Hydraulic Studies

cm

Centimeter

Cu

Uniformity Coefficient

D10

Sieve Diameter Corresponding to 10%

D30

Sieve Diameter Corresponding to 30%

D60

Sieve Diameter Corresponding to 60%

Dd

Drainage Density

Ds

Specific Elevation

ES

Sand Equivalent

Fd

Exceeding Frequency

Fnd

Frequency of Non-exceeding

FSG

Slip Safety Factor

FSR

Rollover Safety Factor

GNSS

Global Navigation Satellite Systems

GPS

Global Positioning System

GTR

Guide to Road Earthworks

HD

Height of the Dike

Hr

Height of the Reservoir

Ic

Consistency Index

Ig

Overall Slope Index

Ip

Plasticity Index

k

Permeability Coefficient

KG

Shape Index

Km

Kilometer

km²

Square Kilometer

L

Length of the Equivalent Rectangle

Lb

Base Width of the Dike

Lc

Ridge Width

m

Meter

DEM

Digital Terrain Model

MRUH

Ministry of Urban Renewal and Housing

NF

French Standard

ORSTOM

Overseas Scientific and Technical Research Office

P

Perimeter of the Watershed

P10

Ten-year Daily Rain

P100

100-year Daily Rain

PVC

Polyvinyl Chloride

Q100

Centennial Flow or Design Flood

Qr10

Ten-year Flow

A

Free Revenge

s

Second

S

Watershed Area

T

Return Period

TN

Natural Terrain

U

Reduced Gumbel Variable

UFR-SI

Engineering Sciences Training and Research Unit

VBS

Methylene Blue Value

w

Water Content

WL

Liquidity Limit

WP

Plasticity Limit

Zd

Setting Dimension
Conflicts of Interest
The authors declare no conflicts of interest.
References
[1] ANSD, «Projection of the population of the Thiès region» 2022.
[2] C. Sophie and L. Jean, “Drinking water service: From the logic of supply to the control of demand,” Jwarp, 1996. Concrete dikes. [Performance]. 2020.
[3] I. SEYE, Design of a rainwater sanitation network integrated into a geographic information system in the Sampathé district, Thiés: UFR SI, 2019, p. 9.
[4] C. MERLIN, “Drinking Supply Project for Cities in the Central and Coastal Zone. Dakar,” (July 2010).
[5] S. Faye, “Hydrodynamic modeling of the aquifers of the northern coast between Kayar and Saint-Louis. Impact of future withdrawals envisaged within the framework of the water supply of Dakar and its surroundings,” Dakar, 1995.
[6] B. Igor and G. Didier, “Tool to aid in the diagnosis of the drinking water network for the city of Chisinau by spatial and temporal analysis of hydraulic dysfunctions,” jwarp, 2004.
[7] M. AVERETTE, 2005. [Online]. Available:

http://fr.scienceaq.com/

[8] SETICO/CONCEPT, “Possible variants of water resource mobilization,” 2013.
[9] C. M. S. SONES, “Mobilization of alternative water resources for irrigation in the Dakar region. 79 p.,” 2007.
[10] M. D. KHOUSSA, “Study of the dike,” at Hydrological Analysis-Diagnostic of the Sibidiang dam in the commune of Medina Gounass, UFR-SET, 2020, p. 60.
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    Camara, N., Niane, B., Tamba, S. (2024). Solution to the Breach of the Dike of Keur Bara KAIRE, Located in the Commune of Notto Diobasse in the Department of Thiès, Senegal. Journal of Civil, Construction and Environmental Engineering, 9(6), 197-210. https://doi.org/10.11648/j.jccee.20240906.13

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    ACS Style

    Camara, N.; Niane, B.; Tamba, S. Solution to the Breach of the Dike of Keur Bara KAIRE, Located in the Commune of Notto Diobasse in the Department of Thiès, Senegal. J. Civ. Constr. Environ. Eng. 2024, 9(6), 197-210. doi: 10.11648/j.jccee.20240906.13

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    AMA Style

    Camara N, Niane B, Tamba S. Solution to the Breach of the Dike of Keur Bara KAIRE, Located in the Commune of Notto Diobasse in the Department of Thiès, Senegal. J Civ Constr Environ Eng. 2024;9(6):197-210. doi: 10.11648/j.jccee.20240906.13

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  • @article{10.11648/j.jccee.20240906.13,
  author = {Ndiouga Camara and Birane Niane and Séni Tamba},
  title = {Solution to the Breach of the Dike of Keur Bara KAIRE, Located in the Commune of Notto Diobasse in the Department of Thiès, Senegal
},
  journal = {Journal of Civil, Construction and Environmental Engineering},
  volume = {9},
  number = {6},
  pages = {197-210},
  doi = {10.11648/j.jccee.20240906.13},
  url = {https://doi.org/10.11648/j.jccee.20240906.13},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.jccee.20240906.13},
  abstract = {This article studies the rupture of the Keur Bara KAIRE dike, located in the commune of Notto Diobasse in the department of Thiès in Senegal. The village is crossed by a stream which collects rainwater from the west to the east, following a natural slope. The overflow of this stream causes serious flooding, leading to the total cutting of the road and the isolation of the population. These floods had tragic consequences, resulting in two losses of human life. To regulate the water level, prevent flooding and protect agricultural and urban areas from overflows, the Senegalese authorities initiated the project to build the Keur Bara KAIRE dike in 2004, unfortunately the latter gave way in 2017. The geotechnical analysis was carried out on samples taken from various points on the site, revealing that the terrain is mainly composed of fine sand and the embankment is made with clayey sand. Morphometric and hydrological investigations highlight that the watershed of the Keur Bara KAIRE dike covers an area of 3.72 km², with a projected flow of 54.99 m³/s. The resizing of the dike revealed the following data: a length of 132 meters and a height of 3 meters. The spillway is 52.99 meters long with a reservoir height of 1.22 meters. The bay walls have a thickness of 50 cm and the embankments have a slope of ½ upstream and downstream. The stability calculation on the broken dike reveals a sliding safety factor (FSG) of 1.84 which complies with the standard and an overturning safety factor (FSR) of 0.13 which is not verified. The surface of the watershed which is equal to 3.72 km², also the smallest height of precipitation is equal to 234.9 mm and the largest 664.4 mm, the ORSTOM and CIEH methods for hydraulic calculations.
},
 year = {2024}
}

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  • TY  - JOUR
T1  - Solution to the Breach of the Dike of Keur Bara KAIRE, Located in the Commune of Notto Diobasse in the Department of Thiès, Senegal

AU  - Ndiouga Camara
AU  - Birane Niane
AU  - Séni Tamba
Y1  - 2024/11/28
PY  - 2024
N1  - https://doi.org/10.11648/j.jccee.20240906.13
DO  - 10.11648/j.jccee.20240906.13
T2  - Journal of Civil, Construction and Environmental Engineering
JF  - Journal of Civil, Construction and Environmental Engineering
JO  - Journal of Civil, Construction and Environmental Engineering
SP  - 197
EP  - 210
PB  - Science Publishing Group
SN  - 2637-3890
UR  - https://doi.org/10.11648/j.jccee.20240906.13
AB  - This article studies the rupture of the Keur Bara KAIRE dike, located in the commune of Notto Diobasse in the department of Thiès in Senegal. The village is crossed by a stream which collects rainwater from the west to the east, following a natural slope. The overflow of this stream causes serious flooding, leading to the total cutting of the road and the isolation of the population. These floods had tragic consequences, resulting in two losses of human life. To regulate the water level, prevent flooding and protect agricultural and urban areas from overflows, the Senegalese authorities initiated the project to build the Keur Bara KAIRE dike in 2004, unfortunately the latter gave way in 2017. The geotechnical analysis was carried out on samples taken from various points on the site, revealing that the terrain is mainly composed of fine sand and the embankment is made with clayey sand. Morphometric and hydrological investigations highlight that the watershed of the Keur Bara KAIRE dike covers an area of 3.72 km², with a projected flow of 54.99 m³/s. The resizing of the dike revealed the following data: a length of 132 meters and a height of 3 meters. The spillway is 52.99 meters long with a reservoir height of 1.22 meters. The bay walls have a thickness of 50 cm and the embankments have a slope of ½ upstream and downstream. The stability calculation on the broken dike reveals a sliding safety factor (FSG) of 1.84 which complies with the standard and an overturning safety factor (FSR) of 0.13 which is not verified. The surface of the watershed which is equal to 3.72 km², also the smallest height of precipitation is equal to 234.9 mm and the largest 664.4 mm, the ORSTOM and CIEH methods for hydraulic calculations.

VL  - 9
IS  - 6
ER  -

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Author Information

  • Ndiouga Camara

    Geotechnical Department, UFR Engineering Sciences, Iba Der THIAM University of Thiès, Thiès, Sénégal

    Contact Email

  • Birane Niane

    Geotechnical Department, UFR Engineering Sciences, Iba Der THIAM University of Thiès, Thiès, Sénégal

  • Séni Tamba

    Civil Engineering Department, Polytechnic School of Thiès, Thiès, Sénégal

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