Characteristics of Sediment Material at Bengkalis River Bengkalis

Regency, Riau

Dedi Enda, Zulkarnain and Oni Febriani

Department of Civil Engineering, State Polytechnic of Bengkalis, Jl. Bathin Alam, Sungai Alam,

Bengkalis Distric of Riau Province, Indonesia

Keywords: Sediment Characteristics, The Bengkalis River, Sediment Analysis.

Abstract: One of the causes of decreasing river capacity is silting and/or narrowing by sedimentation, this is what

happened in the Bengkalis River, another impact due to siltation is the occurrence of overflowing water from

the river which can threaten the area on the riverbank, so research is carried out on the characteristics of

sediment samples, especially the Bengkalis river with the aim to obtaining information about the

characteristics of river sediments. The method used in this research is field observation by measuring the river

profile and flow velocity, then taking soil samples at the riverbed and carrying out laboratory tests such as

specific gravity, filter analysis, and hydrometer. The results of BJ sediments from three sediment samples at

the estuary, middle and upstream locations of STA 0+000, STA 0+925, and STA 1+922 were 2.46; 2.26; and

2.37. Based on the results of laboratory tests, the results of the specific gravity show that the farther from the

sea, the smaller the density of the sediment. The types of sedimentary material from the results of the sieve

analysis and hydrometer test are silt (silt) and clay, respectively STA 0+000 37.84%, 19.81%, STA 0+925

42.46%, 31.01%, and STA 1 +922 50.07%, 28.82%.

1 INTRODUCTION

A river is a natural and/or artificial water channel or

container in the form of a water drainage network and

the water in it, starting from the upstream to the

estuary, bordered on the right and left by border lines

(PP No. 38, 2011).

The river is a flow of water that flows from

upstream to downstream and this river flow moves

from a high place to the lowest or shallow place.

River water always flows in one direction because the

river is located on the lower part of the earth's surface

than the surrounding land, which comes from

mountain water which then empties into one place,

namely the sea (Andini and Nisye, 2017).

The river consists of a river trough and a river

border. The space for flowing water is located in the

riverbed and as a place for the life of the river

ecosystem to take place, so that in essence rivers and

their tributaries play an important role in

accommodating, storing, and draining water that

comes from rainfall to the sea naturally. The success

of rivers in carrying out their functions minimizes the

risk of flooding, especially in urban areas (PP No. 38,

2011).

The river has its own capacity to be able to ward

off flooding. One of the causes of decreasing river

capacity is due to silting and/or narrowing by

sedimentation.

Sedimentation is a process of entering sediment

loads into a certain aquatic environment through

water media and being deposited in that environment.

Sedimentation that occurs in coastal and river

environments becomes a problem if it occurs in

locations where there are human activities that require

clean water conditions (Triatmodjo, 1999).

There are several causes of sedimentation,

including the deposition of river water, sea water

deposition. This deposition process will result in

sediment consisting of several materials with various

sizes of soil particles depending on the parent

material that composes them. Some materials that

often become sediment, including: sand and clay. The

type of sediment according to the particle size can be

found dissolved in the river or what is called the

suspended load and the sediment that creeps on the

riverbed is called the bed load (Triatmodjo, 1999).

The difference between sediment load and

creeping sediment can be seen by looking at the

movement of the sediment particles. The movement

518

Enda, D., Zulkarnain, . and Febriani, O.

Characteristics of Sediment Material at Bengkalis River Bengkalis Regency, Riau.

DOI: 10.5220/0010948500003260

In Proceedings of the 4th International Conference on Applied Science and Technology on Engineering Science (iCAST-ES 2021), pages 518-525

ISBN: 978-989-758-615-6; ISSN: 2975-8246

 2023 by SCITEPRESS – Science and Technology Publications, Lda. Under CC license (CC BY-NC-ND 4.0)

of these particles is influenced by flow velocity, river

morphology, riverbed roughness and river slope.

These parameters interact with each other so that it

will determine the amount and type of sediment and

the speed of sediment transport, this causes the results

of the sedimentation process in one place to another,

even though it is in one coastal area, as well as for the

Bengkalis island area which is on the coast of the

Malacca strait.

The source of origin of sediment is one of the

factors that cause differences in characteristics.

Waikelo Beach and Melolo are beaches facing the

Sumba Strait and facing the surrounding islands

(Flores Island and Sumbawa Island) so that the

coastal sediments have a major influence on the

sediment supply from the mainland. Meanwhile, the

Laboya beach is directly related to the Indian Ocean

which causes the size of the coastal sediment to be

smoother. The same thing was expressed by Nugroho

and Putra (2017), who conducted research on the

grain size of sediments in the Sumba Strait and to the

south and west of the Indian Ocean, that sediments

that are directly related to the Indian Ocean have a

smoother character than those in the Sumba strait.

The results of the calculation of the sediment

fraction of the waters of the Silandak River (Table 2)

sedimentary classification is dominated by sand

(sand) and clay (clay). Sand is found at points 1,2, and

3 where point 1 is upstream, points 2 and 3 are part of

the middle river, where the three points are areas with

a depth of < 30 cm and a low river current speed of

0.04 seconds. The condition around the river is in the

form of densely populated settlements, around the

river rocks and sand are found, so that the sediment

that is deposited in the form of sand, other fine

materials is carried by currents into lower waters to

the sea. Points 4 and 5 are dominated by clay with an

average clay percentage of 60%, this is because points

4 and 5 are parts close to the coast where fine particles

carried from upstream will enter downstream

(Dominig and Muskananfola, 2019).

Analysis of sedimentation characteristics has been

carried out in the New Straits port area at the mouth

of the Bengkalis Liong River, where the Liong River

estuary is located on the north coast of Bengkalis

Island which is directly connected to the Malacca

Strait. Analysis of sediment characteristics was

carried out at 2 station points in the New Straits port.

From the results of the sedimentation analysis, it was

found that there were three sediment fractions,

namely sand, silt and clay with various diameters.

The percentage of sand at station 1 is 75.87% which

is located in the port dock area, while the percentage

of sand at station 2 is 53.9%, precisely at the end of

the river mouth. The percentage of silt at station 1 is

20.85%, while at station 2 is 43.86%. The percentage

of clay at station 1 is 3.28%, while at station 2 is

3.24% (Khabib et all, 2013).

Research on sediment characteristics was also

carried out on the Selatbaru beach with a location

distance of +1 km (Khabib et all, 2013), where the

results obtained that the sediment characteristics of

the beach bottom surface were grouped into three

sedimentary fractions, namely gravel, sand and mud.

The sand sediment fraction is found at each station

and is the most common sedimentary sediment found

when compared to the gravel and mud fractions. The

type of sediment in the research location can be

grouped into 2 types of sediment, namely sand and

muddy sand. Sediment with sand type is found in

every sub-station, except for sub-station 1B which

has a muddy sand fraction type (Putra et all, 2017).

Study of sediment characteristics on the west

coast of Bengkalis Island, the study was carried out

by taking test samples using the Eckman Grab from 7

station points (Figure 1) then analyzed to determine

the composition and content of organic matter in the

sediment, where the results of the analysis of the

sediment fraction in the waters The Bengkalis Strait

shows that these waters consist of three types of

fractions, namely gravel, sand, and mud. However,

the dominant fraction in each station is the sand

fraction (Putri and Rifardi, 2012).

Figure 1: Sample station of Putri and Rifardi research,

2012.

The percentage of gravel fraction ranges from 0-

17.84% where the lowest percentage is at Stations 2,

3, and 5 while the highest percentage is at Station 4

with a percentage of 17.84%. The percentage of sand

fraction ranges from 80-96.72% where the highest

Characteristics of Sediment Material at Bengkalis River Bengkalis Regency, Riau

519

percentage is at Station 2 and the lowest is at Station

4. While the percentage of mud fraction is around

2,1618.42% where Station 4 is the lowest percentage

and Station 3 is the highest percentage. The type of

sediment fraction in these waters is dominated by

sand at each station (Putri and Rifardi, 2012).

Bengkalis River is one of the rivers in the

Bengkalis District with a total length of 3.81 km from

upstream to downstream. The location of the

Bengkalis river is in the coastal area so that the

condition of the river water level is strongly

influenced by the conditions of the tides and the ebb

and flow of sea water. Visual observation of several

sea segments of the Malacca Strait sedimentation

occurs (Figure 1).

The occurrence of sedimentation is strongly

supported by the condition of the river which has a

water flow at high tide that is greater than the flow at

low tide, so that the material carried by water

upstream during high tide will experience

sedimentation.

Over time, sedimentation that occurs in the

Bengkalis river results in greater siltation and causes

a reduction in the capacity of the river so that it has

the impact of overflowing water that threatens the

area on the outskirts of the river from the danger of

flooding, so it is necessary to do research on the

characteristics of sediment samples, especially the

Bengkalis river. Based on the description above,

research was conducted with the aim of obtaining

information about the characteristics of sediments in

the Bengkalis river, the results of this study can be

used as an initial reference in handling river

sediments, especially the Bengkalis river.

Besides that, the results of this test must include

SNI 3423:2008:

a. Percentage of grain greater than 2.00 mm;

b. The percentage of coarse sand 2.0 mm to 0.42

mm;

c. Percentage of fine sand, 0.42 mm to 0.074 mm;

d. Percentage of silt 0.074 mm to 0.002 mm;

e. The percentage of clay is less than 0.002 mm

and;

Colloidal percentage is smaller than 0.001 mm.

2 METHOD

The method implemented in this study is a field

observation method in the form of a field survey to

obtain input data needed in analyzing sediment

characteristics and by conducting tests at the Soil

Testing Laboratory of the Civil Engineering

Department of the Bengkalis State Polytechnic. The

stages of research implementation are as follows:

Figure 2: Research Flowchart.

To determine the characteristics of the Bengkalis

river sediment, a test sample is needed, the sediment

test sample used is the test material (sediment) which

represents the sediment that occurs in the Bengkalis

river, namely the test sample from STA 0+000, STA

0 +925 and 1 + 922. Location of position each point

of sediment sampling can be seen in Table 1 and

Figure 3, Figure 4, Figure 5 and Figure6. For each

STA 3 representative sediment samples were taken.

Table 1: Coordinate Sampling Points.

No STA River Basin Coordinate

1 0 + 000

Downstream/

Estuar

102

7’10,299” E

27’37,772” N

2 0 + 925 Middle

102

7’18,327” E

28’2,051” N

3 1 + 922 Upstrem

102

7’17,888” E

28’30,434” N

The stages of this research include the following

activities:

2.1 Data Collection Stage

Data collection includes measurement of river cross-

section, river flow velocity and sediment sampling.

Measuring the cross section of the river to determine

the dimensions of the river using the Theodolite

measuring instrument and drawing using AutoCad

software. Measurement of the speed of river currents

in a cross-sectional area of the river by using a

measuring instrument Currentmeter.

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520

Figure 3: Research locations and sampling points in the

estuary, middle and upstream of the river in Bengkalis

Island.

Figure 4: Research locations STA 0+000.

Figure 5: Research locations STA 0+925.

Figure 6: Research locations STA 1+922.

Sediment Sampling was taken at several points,

namely at STA. 0 + 000, STA. 0 + 925 and STA. 1 +

922 by using a sediment sampler which will then be

tested for its characteristics at the Soil Testing

Laboratory.

Figure 7: Sampling of riverbed sediment.

2.2 Laboratory Testing Stage

This stage includes the activities of several sediment

sample testing to determine the characteristics of the

sediment. There are several tests carried out:

2.2.1 Sediment Specific Gravity Test (GS)

Specific gravity is the ratio between the density of soil

grains and the density of distilled water at the same

temperature and volume. The test uses a pycnometer

and a test object that passes the No. sieve. 40 (SNI

1964, 2008).

The sequence of processes in the specific gravity

test is as follows:

1. Preparation of tools including pycnometer (in

clean condition) and test sample

2. Weigh the pycnometer (W1)

3. Fill the pycnometer with water up to the

specified limit and then weigh the pycnometer +

water (W4)

Characteristics of Sediment Material at Bengkalis River Bengkalis Regency, Riau

521

4. Enter the test sample into the pycnometer to a

predetermined limit, then weigh the pycnometer

+ soil weight (W2)

5. Fill the pycnometer with water and gently shake

the pycnometer so that there are no more water

pores. Heat the water until it boils and put the

pycnometer in the pot, then the air bubbles will

evaporate until the air bubbles disappear. Lift

the pycnometer if the air bubbles are no longer

there, add water to the pycnometer to the

specified limit and let the pycnometer stand for

24 hours.

6. Weigh the pycnometer + water + the sample that

has been set aside (W3)

7. Analysis of sediment density calculation

Calculating the density of sediment using the

formulation

Gs = (W

-W

)/(W

-W

)-(W

-W

) (1)

Where:

Gs = Density of soil

W1 = Weight of pycnometer (grams)

W2 = Weight of pycnometer and dry sample

(grams)

W3 = Weight of pycnometer, sample and

water (grams)

W4 = Weight of pycnometer and water

(grams)

Figure 8: Specific Gravity Test of Sediment Samples.

2.2.2 Sieve Analysis Test

This test was carried out to obtain the grain size

distribution of the soil using sieve analysis. The test

object used was an oven-dried sediment sample. The

process in testing sieve analysis is as follows:

1. The test object is dried in an oven at a

temperature of (110 + 5 C).

2. Weigh the sieve used in an empty state.

3. Take a sample weighing 2000 grams.

4. Put the sample into the plastic and soak for + 1

hour.

5. After 1 hour, wash the sample above 1 set of

filters until the color of the water entering the

filter is the same as the water coming out of the

filter.

6. Put the sample retained on each sieve into

different containers and code according to the

sieve number.

7. Oven sample in container for 24 hours

8. Weigh and record the weight of the oven dry

sample.

The filter analysis test with the following sieve

size (SNI 3423, 2008):

Table 2: Sieve Size.

# Sieve ø

(

)

2,5" 63,5

1,5" 38,1

1" 25,4

3/4" 19,05

3/8" 9,525

No. 4 4,75

No. 10 2,000

No. 20 0,850

No. 40 0,425

No. 100 0,150

No. 200 0,075

Figure 9: Wet method sieve analysis (washing).

2.2.3 Hydrometer Test

The hydrometer test is a test carried out to calculate

the grain size distribution of a fine-grained soil or the

fine-grained portion of a coarse-grained soil based on

the sedimentation of the soil in water, sometimes also

called the sedimentation test.

In the hydrometer test, the tested soil sample is

dissolved in water in a dispersed state, the soil grains

will drop freely to the bottom of the vessel. The

settling speed of the soil grains varies depending on

the size of the soil grains. The largest soil particles

will settle first with a greater settling velocity. The

process in testing the hydrometer analysis is as

follows SNI 3423, 2008 :

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522

1. Prepare tools and test samples that pass the No.

sieve. 200 which has been oven-dried weighing

50gr.

2. Weigh the kalgon to be used weighing 15 grams.

3. So that the soil settles Pour a little water on the

sample and leave it for 10 minutes.

4. Fill 30 ml of water into the first measuring cup,

put kalgon into the water and stir until dissolved.

After dissolving add water until the volume of

water becomes 1000 ml.

5. Fill 1000 ml of water in the second measuring

cup.

6. Fill 1000 ml of water in the third measuring cup

7. Close the second measuring cup and shake for

60 times

8. Place the first, second and third measuring cups

in a parallel position, turn on the stopwatch for

2 minutes, take the hydrometer and temperature

readings on the 2nd measuring cup.

9. Lift the hydrometer and thermometer and clean

it, calculate the hydrometer and temperature in

the first measuring cup

10. Do the same steps at a time of 5 minutes, 15

minutes, 30 minutes, 60 minutes, 240 minutes

and 1440 minutes.

Figure 10: Hydrometer Test.

3 RESULTS AND DISCUSSION

In this study, researchers conducted an examination

of the specific gravity of the sediment obtained by the

test results as shown in Table 3 and Figure 11.

From table 4, it is known that the speed and

discharge of water at low tide decreases from

downstream to upstream. Likewise, the speed and

discharge of water at high tide decreases from

downstream to upstream. However, the speed of the

water at low tide is higher than the speed of the water

at high tide. however, the water discharge at low tide

that occurs at STA 0+925 and STA 1+922 is greater

than at high tide.

Table 3: Specific Gravity of Bengkalis River Sediment.

Description

STA

0 + 000 0 + 925 1 + 922

Empty pycnometer weight (M

)

(gr)

88.10 96.90 172.53

Weight of pycnometer + dry soil

(

)

151.10 157.13 299.50

Weight of pycnometer + soil +

water (M

) (gr)

371.37 380.63 741.90

Weight of pycnometer + water

) (gr)

336.23 344.87 668.50

Temperature t °c (degrees) 29.17 29.00 29.17

Dry soil weight (A = M

–

)

(gr)

63.00 60.23 126.97

Weight of soil in water (B = M

) (gr)

35.13 35.77 73.40

C = A- B 27.87 24.47 53.57

Specific gravity Gs = A / C 2.26 2.46 2.37

G for 27.5 °c = Gs * (Bj. Water t

°c/B

. Wate

27.5 °c

)

1923.41 2069.67 2017.30

Figure 11: Specific Gravity of Sediment at 3 observation

stations.

Table 4: Specific gravity, velocity and river discharge.

Description Unit

STA

0 + 000 0 + 925 1 + 922

Specific Gravity

2.26 2.46 2.37

Average speed of

low tide

m/s 0,133 0,039 0,036

Average

Discharge of Low

tide

/s 3,137 1,254 0,194

The average

speed of the tide

m/s 0,088 0,037 0,030

Average High

Water Dischar

/s 4,27 1,143 0,162

According Table 3 and Figure 11, it can be seen

that there are differences in the density of sediment in

each STA, where the density of sediment at STA

0+925 is greater than the density of sediment at STA

0+000 and STA 1+922. This difference is influenced

by the position of the STA. Sampling at STA 0+000

Characteristics of Sediment Material at Bengkalis River Bengkalis Regency, Riau

523

is in the estuary area, STA 0 + 925 is in the middle of

the length of the river and is in the area after the

bridge, while STA 1+922 is in the upper part of the

river. The deposition at the end of the river mouth

(STA 0+000) is smaller due to ship wave activity and

the influence of tidal currents is greater than in the

areas of STA 0 + 925 and STA 1+922.

Different results were also obtained a study for

one of the rivers on the island of Bengkalis (Liong

River) (Khatib et all, 2013), the density of sediment

at station one (2,551) and station two (2,569), where

the density of sediment at station two was greater than

that at station two. with the sediment density of

station one. This difference is influenced by the

position of the station. Sampling at station one is in

the port dock area, while station two is at the end of

the river mouth. The deposition at the end of the river

mouth is caused by ship waves and the influence of

tidal currents is greater than in the area near the harbor

pier. That even though the rivers are in the same

island, the specific gravity of the sediment deposits

has different characteristics.

Table 5: Analysis of sediment grains.

Sieve Analysis

ø (mm)

% Pass

0 + 000 0 + 925 1 + 922

63,5 100,00 100,00 100,00

38,1 100,00 100,00 100,00

25,4 99,37 100,00 100,00

19,05 98,45 95,01 99,15

9,525 97,98 92,68 98,48

4,75 97,41 91,90 98,10

2,000 96,15 91,53 97,49

0,850 94,24 90,95 96,20

0,425 87,74 89,86 94,95

0,150 79,92 85,84 91,55

0,075 65,14 83,23 90,55

Hydrometer Analysis

0 + 000 0 + 925 1 + 922

Diameter

(mm)

% Pass

Diameter

(mm)

% Pass

Diameter

(mm)

% Pass

0,0307 35,33 0,0289 49,38 0,0300 47,83

0,0203 27,30 0,0190 40,77 0,0195 40,47

0,0121 18,74 0,0114 32,73 0,0116 34,34

0,0087 14,99 0,0082 29,29 0,0083 30,05

0,0062 16,06 0,0059 24,69 0,0060 26,37

0,0031 11,51 0,0030 18,95 0,0030 19,62

0,0013 7,49 0,0013 9,76 0,0013 11,65

Figure 12: Grain size distribution of Bengkalis river

sediment.

For testing the grain size distribution analyzed by

hydrometer analysis and sieve analysis and presented

in the form of a cumulative weight percentage curve.

The test results can be seen in table 5 and Figure 12

below.

The form should be completed and signed by one

author on behalf of all the other authors. The grain

size of sediment can be grouped as follows:

Table 6: Grouping of Bengkalis river sediment grain size.

Sediment Grain

Size

STA 0+000 STA 0+925 STA 1+922

Gravel 3,853 8,467 2,510

Coarse San

8,403 1,677 2,540

Fine San

22,60 6,63 4,40

Silt 37,84 42,46 50,07

Cla

19,81 31,01 28,82

Colloids 7,49 9,76 11,65

Figure 13: Bengkalis river sediment grain size grouping.

From table 6 and figure 13 it is known that the

dominant types of sedimentary material in the

Bengkalis river are silt (silt) and clay, respectively

STA 0+000 37.84% and 19.81%, STA 0+925 42.46%

and 31 0.01% and STA 1+922 50.07% and 28.82%.

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524

The percentage of silt has increased from downstream

to upstream. In contrast to the sediment content of the

Liong Bengkalis river (Khatib et all, 2013), which is

dominated by 75.87% sand (station 1) and 53.9%

(station 2) while silt is 20.85% (station 1) and 43.86%

(station 2 ). The results of this study are also very

different from the results of research on sediment

deposits in the Bengkalis strait (Putri and Rifardi,

2012), the percentage of sand fraction and gravel

fraction dominates the type of sedimentary material

ranging from 80-96.72% and 0-17.84%, so it can be

concluded it is stated that the type of sedimentary

material between the river and the sea where the river

empties has different materials.

Figure 14: Location Research of Sediment.

4 CONCLUSIONS

Based on the results of data analysis that has been

carried out, conclusions can be drawn including

Density of sediment from the dominant sedimentary

material, respectively STA 0+000 2,26, STA 0+925

2,46 and STA 1+922 2,37.

The type of sedimentary material that dominates

the Bengkalis river sediment deposits are silt (silt)

and clay, respectively STA 0+000 37.84% and

19.81%, STA 0+925 42.46% and 31.01% and STA

1+922 50.07% and 28.82%.

The type of sedimentary material that dominates

the sediment in the Bengkalis river is different from

the type of sedimentary material in the Bengkalis

strait where the Bengkalis river estuary.

ACKNOWLEDGEMENTS

The research team would like to thank the Bengkalis

State Polytechnic Research and Community Service

Center for funding the initial stages of this research,

and hope to be willing to contribute to the next

follow-up research. To the team members who

always contribute to this research activity so that it

can be completed within the allotted time.

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