The slide is related to the sedimentation process , on lake ,bottom dynamics on the lake and formation of paleo lake described briefly in the presentation slide

1. CONTROLS ON LAKE SEDIMENT
TRANSPORT AND ACCUMULATIONS
Presentation by:
Roshan Paudel
Tribhuwan University
mail2roshanji@gmail.com

2. Table of content
 Controls on lake sediment transport and accumulations
 Kinematics of lake water
 Process regulate the control on sediments and contaminants
 Transport, sedimentation and resuspension
 Resuspension of Lake sediments
 Determination of bottom dynamic condition in lakes
 Post depositional process
 A chemical classification of elements in lake sediments
 Rhythmites
 Lake level fluctuations
 Formation of Kathmandu lake and sedimentation

3. Controls on lake sediment transport and accumulations
• The sedimentological
conditions in a lake will
influence almost all process
in the aquatic ecosystem.
• Within a lake several
process regulate and control
the pathways of sediments
and contaminants.
Figure 1:Illustration of general and fundamental transport process.

4. Kinematics of lake water
Figure 2: Penetration of solar radiation and temperature profile
in crooked lake, Indiana, 18 July 1964.

5. Figure 3: Temperature profile and inferred circulation in different types of the
water column of lake Tanganyika.

6. Currents in lake
Figure 4 : a) Distribution mechanism and resulting sediment types dues to currents.
b) Tubidite in lake dues to currents in lake.

7. Process regulate the control on
sediments and contaminants
1. Sedimentation: the transport
of matter from water to
sediments
2. Resuspension: the transport of
matter from sediment to back
to water
3. Diffusion: the transport
dissolved substance from
sediments back to water
4. Mineralization: the bacterial
decomposition of organic
matter
Figure 5: Mechanism and interaction of
sediments in the lake.

8. 5. Mixing: the upward and
downward transport of matter.
6. Bioturbation: the mixing of
deposited materials from
movement of the bottom fauna.
7.Compaction : the vertical
change in sediment water
content and sediment density
due to the weight of overlying
sediments.
8. Burial: the transport from
biologically active sediments to
bio passive sediments.
Figure 6: Controlling factors on lake sediment.

9. Figure 7 : Flow chart showing how sedimentation is happen in the Lake.

10. Figure 8: Source process, transportation and deposition of sediment in lake.

11. Figure 9: Sedimentation in shallow and deep lake.

12. Transport, sedimentation and resuspension
• The process of sedimentation
burial and resuspension are
interlinked and to understand
them requires an
understanding of bottom
dynamic condition within a
lake.
• In defining the bottom
dynamic condition (erosion
transportation and
accumulation), definitions
used are; Figure 10: the erosion transportation and
accumulation diagram showing relation between
effective fetch and water depth.

13. • Areas of erosion(E)
This area prevail where there is no apparent deposition of fine material
but rather a removal of such material, for example in shallow areas or
on slopes; E areas are generally hard and consists of sand gravel
consolidated clays and or rocks .
• Areas of transportation(T)
This area prevail where fine materials are deposited periodically (areas
of mixed sediments).this bottom type generally dominates where wind
wave action regulates the bottom dynamic condition as shown in figure
10. it sometimes difficult in practice to separate areas of erosion from
areas of transportation

14. • Areas of accumulation(A)
This area prevail where the fin materials are deposited continuously.
Owing to their fine grained nature these are areas where high
concentration of pollutants may appear.
Figure 11: Illustrations of major sedimentological process.

15. Area of accumulation (Condt..)
• The water content , graine size and /or the composition of the
material are often used as criteria to distinguished different sediment
types as shown in table 1.
• From the stokes equation for settling particles as well as for
convenience, the limit between coarsed and fine materials can be set
at a particle size of medium silt (0.06mm).
• Generally sandy sediments within the areas of erosion and transport
(ET) often have a low water content , low organic content and low
concentrations of nutrients , low benthic biomass and few
containments.
• The conditions within the T areas are ,for natural reasons, variable,
especially for the most mobile substances, such as phosphorus,
manganese and iron, which may react rapidly to alterations in
sediment chemical.

16. Figure 12 :Compilation of concepts related to sediment-living organisms (zoobenthos,
benthic algae and macrophytes) (see also Vollenweider 1968, 1976; Cummings 1973;
Brinkhurst 1974; Wetzel 2001).

17. Table 1: The relationship between bottom dynamic conditions (E,T,A) and
the physical, chemical and biological character of the surficial sediments of
Lake Lilla Ullevi Bay (in Lake Mälaren).
Category Characteristic Erosion
(n = 15)
Transportation
(n = 10)
Accumulation
(n = 14)
Physical
parameters
Water depth (m) Water
content (% ww) Bulk
density (g cm−3) Organic
content
(loss on ignition, %dw)
13.0 (0.41)
32.6 (0.28)
1.71(0.087)
4.6 (0.48)
17.5 (0.31) 67.4
(0.14) 1.26
(0.079) 10.7
(0.43)
31.6 (0.25)
94.1 (0.024)
1.03 (0.019)
24.3 (0.10)
Nutrients (mg
g−1 dw)
Nitrogen
Phosphorus
Carbon
0.6 (0.67)
0.8 (0.50)
0.5 (1.0)
3.4 (0.35)
2.8 (0.75)
22.7 (0.74)
10.7 (0.14)
1.6 (0.31)
10.4 (0.16)
Benthic
biomass (mg
ww m−2)
1000–2000 3000–4000 6000–7000
Chemically
mobile
elements (see
also P) (mg g−1
dw) Metals (μg
g−1 dw)
Iron
Manganese
Zinc
Copper
Nickel
24.6 (0.42)
0.8 (1.0)
41 (0.46)
18 (0.50)
23 (0.35)
53.5 (0.27)
3.5 (0.74)
111 (0.24)
31 (0.42)
40 (0.20
41.3 (0.077)
2.5 (0.60)
189 (0.090)
59 (0.10)
57 (0.18)

18. Contd.
• Fine material may be deposited for longer periods during stagnant
weather conditions.
• In connection with the a storm or a mass movement on a slope,
this materials may be resuspended and transported, generally in
the direction towards the A areas in the deeper parts,where
continuous deposition occurs. Thus resuspension is a natural
phenomena on T areas.
• It should be stressed that the fine materials are rarely deposited as
a result of simple vertical settling in natural aquatic environments.
• The horizontal velocity component in the lake water is generally
at least ten times lager, some times up to 10000 times larger, than
the vertical component for materials or flocs which settle
according to stokes law.

19. Resuspension of Lake sediments
• Resuspension is the physical (advective) transport of matter from
sediments back to water and mixing is the upward and downward
transport of dissolved and suspended particulate matter across the
thermocline (the thermocline is the zone in the water that separates
the warmer, lighter surface water from the colder, heavier deep
water).
• Some lakes are constantly mixed and do not develop a thermocline,
but most lakes, and certainly those in northern and boreal
landscapes, develop a thermocline in the summer.
• The surface water (the epilimnion) is fundamental for the primary
production of matter. Many important sedimentological processes
take place in the deep-water zone (= hypolimnion).

20. Resuspension
There are some basic rules regulating sedimentation in lakes (e.g.
Thomas et al. 1976; Golterman et al. 1983; Håkanson & Jansson 1983;
Colman et al. 2000; and Figure 11).
• River action dominates the sedimentological properties in river-
mouth areas, where deltas may be formed if the amount of sandy
materials carried by the tributaries is large enough. Within these
areas, sedimentation rates generally decrease with distance from the
mouth, and so does the grain size of the settling particles.
• In open-water areas, dominated by wind/wave action,
sedimentation rates generally increase from the wave base to the
deepest parts of the lakes. The coarsest materials (sand, gravel) are
often found in shallow waters.

21. Figure 13:Wind induced sediment resuspension.

22. Contd..
• Current action can dominate in certain areas, such as in narrow straits and along
the shoreline. Then the ‘Hjulström-curve’ gives the relationship between critical
erosion and critical deposition of materials.
• 4 Slope-induced (gravity) turbidity currents appear on bottoms inclined more than
about 4–5% (Håkanson 1977), and bioturbation generally prevails in oxic
sediments (Table 2), where the macro- and meiofauna cause a mixing of the
sediments

23. Table 2: A geochemical classification (Berner 1981) of sedimentary environments.
Enviroments Depositional character
I. Oxic (CO2 ≥ 10−6 Haematite, goethite, MnO2-type minerals; no
organic matter
II. Anoxic (CO2 < 10−6)
A. Sulphidic (CH2S ≥ 10−6)
B. Non-sulphidic (CH2S < 10−6)
1. Post-oxic
2. Methanic
Pyrite, marcasite, rhodochrosite, alabandite;
organic matter Glauconite and other Fe2+–Fe3+
silicates (also siderite, vivianite, rhodochrosite);
no sulphide minerals; minor organic matter
Siderite, vivianite, rhodochrosite; earlier formed
sulphide minerals; organic matter.
C is the concentration (moles L−1 )
H2S is total sulphide

25. Determination of bottom dynamic condition in lakes
The following processes influence internal loading and bottom
dynamic (E T and A) condition in lakes (Håkanson & Jansson 1983):
• an energy factor related to the effective fetch and the wave base
(see the ETA diagram in Figure 10);
• a form factor related to the percentage of the lake bed above the
wave base (see Figure 14); and
• a lake slope factor related to the fact that slope-induced
transportation (turbidity currents) may appear on bottoms inclining
more than 4–5%

26. Figure 14 :Illustration of major sedimentological and bottom-dynamics
processes in lakes. (Modified from Håkanson & Jansson 1983.).

27. Post Depositional Process
• Bioturbation :Bioturbation is the mixing of the deposited materials
from the movement (eating, digging and foraging activities) of the
bottom fauna (zoobenthos).
• The sediment classification scheme in table 2 focuses on the oxygen
status of the sediments.
• Zoobenthos will not generally survive if the oxygen concentration at
the sediment–water interface becomes lower than about 2 mg L−1.
When the zoobenthos die, the biological mixing (bioturbation; see
Figure 15) of the sediments will stop.
• This has profound consequences for the lamination of the sediments
and, hence, has implications for interpretations about the age
distribution of sediments.

28. Figure 15: Illustration of key processes related to bioturbated sediments
(sedimentation, upward and downward biotransport, substrate decomposition and
compaction). (Modified from Håkanson & Jansson 1983.).

29. Figure 16 :Bioturbation and laminated sediments.

30. Compactional and diagenetic processes
A number of important processes influence sediment accumulation
following deposition :
• These include diffusion, mineralization, compaction and burial.
Diffusion is the chemical transport of dissolved substances from
sediment interstitial water back to lake water regulated by
concentration gradients.
• For many substances (e.g. phosphorus and caesium), the diffusive
transport is highly dependent on sediment redox-conditions – the
lower the redox potential (and oxygen concentrations), the higher the
diffusive fluxes Diffusion may be a dominant flow of phosphorus in
highly productive lakes.
• The function of bacteria in lakes is the decomposition of organic
matter, and mineralization (which produces dissolved substances
during early diagenesis) is the name for this process.

31. Contd..
• Compaction in sediments concerns the vertical change in sediment
water content and bulk density due to the accumulated weight from
overlying sediments.
• The water content may change from about 85% in the uppermost
sediment layer in a lake to about 70% at a sediment depth of 15 cm as
a result of compaction
• As a result, substances deposited on a lake bed may be returned from
sediments back to water by diffusive and advective (= resuspension)
processes.
• There is, however, a sediment depth beneath which substances will
not return. Instead, they will be buried by the constant deposition of
new matter.

32. Figure17 : Compaction and diagenesis of sediments .

33. Figure 18 : Diagenesis model

34. Table 3 : Data from sediment cores from lakes illustrating the relationship
between physical sediment character (the water content of surficial sediment,
0–1 cm, and the sediment constant illustrating the vertical gradient in sediment
compaction) and lake type (From Håkanson & Jansson 1983.)
Lake Lake type Water
content
Sediment
constant
sediment character
Ingen Polyhumic,
oligotrophic
95.2 −0.41 Very loose, small vertical
changes
Trosken Polyhumic,
oligotrophic
95.4 -0.83 Very loose, small vertical
changes
Skal Polyhumic,
oligotrophic
97.4 −0.64 Very loose, small vertical
changes
Hjalmaren Mesohumic,
eutrophic
90.4 −2.99 Loose, clear vertical gradient
Freden Mesohumic,
eutrophic
87.7 −3.80 Loose, clear vertical gradient
Vasman Mesohumic,
mesotrophic
95.9 −3.95 Very loose, clear vertical
gradient
Aspen Mesohumic,
mesotrophic
86.9 −5.78 Loose, strong vertical gradient
Vanern Mesohumic,
oligotrophic
85.5 −5.97 Loose, strong vertical gradient
Vattern Oligohumic,
oligotrophic
92.5 −13.6 Very loose, very strong vertical
gradient

35. A chemical classification of elements in lake
sediments. (Modified after Kemp et al. 1976.
1. Major elements (Si, Al, K, Na and Mg) make up the largest group
of the sediment matrix
2. Carbonate elements (Ca, Mg and CO3–C) constitute the second
largest group; about 15% of the materials
3. Nutrient elements (org.-C, N and P) account for about 10% in
recent lake sediments
4. Mobile elements (Mn, Fe, P and S) make up about 5% of the total
sediment weight
5. Trace elements (Hg, Cd, Pb, Zn, Cu, Cr, Ni, Ag, V, etc.), the
smallest group accounting for less than 0.1% of the sediments

36. Rhythmites
• A regular interbanding of two
or more types of sediment or
sedimentary rocks due to a
regular change in the
conditions of sedimentation,
such as alternation of wet and
dry periods.
• If the individual rhythms can
be shown to represent a single
year’s sediment accumulations,
they are generally called as a
varve. Figure 19: Lake succession

37. Figure 20: Lamination style in offshore areas of an oligotophic lake
depends upon stratification and suspended sediment supply (after
Sturm,1979).

38. Table 4:Chemical characteristics of lake sediments from different
regions of the world (data from Jones & Bowser 1978).
Region Lake/group
type
P Organic
C
Fe Mn Ca k Si Al
Minnesoa
lakes
Low organic
High organic
High carbonate
Low carbonate
0.13
0.17
0.14
0.08
7.6
21
9.9
6.1
5
3.8
2.2
2.5
0.6
0.1
0.15
5
0.9
2
15.2
6.8
1.2
0.7
0.5
o.4
African
lakes
Kivu
Tanganyika
Edvard
Albert
5.3
5
2.4
6.2
0.09
0.03
0.03
0.1
9.5
1.2
3.0
1.4
19
26
29
25
5
10
4.3
12
Great
Lakes
Ontario
Erie
Michigan
Superior
0,07
0.06
0.08
2.3
3.7
2.8
1.5
2.5
0.06
0.06
0.08
0.05
0.4
0.35
11
1.2
2.3
2.2
1.3
0.5
24
26
25
24
5.1
4.8
2.8
2.4

39. Lake level fluctuations
• Lake-level changes can occur as a consequence of climatic change,
tectonic activity, erosion at the outlet, or human activity.
• Water-level fluctuations associated with climate changes are a response to
variations in precipitation-evaporation (P-E) over the watershed.
• A particular lake’s sensitivity to P-E variations is primarily related to basin
hydrology, or whether inflow exits the lake basin via a surface outflow
(overflowing, open) or is confined to the lake basin (non-overflowing,
closed).
• The water level of a closed lake system, in the absence of tectonic
activity, erosion at the outlet, or human influence, represents an
equilibrium state between: (a) input (catchment runoff and
groundwater inflow), and (b) output (evaporation and sub-surface
seepage). In a closed-basin system, changes in effective moisture will
cause the volume of the lake to either increase or decrease until a new
equilibrium is achieved. In overflowing lakes, climatically driven lake-
level changes.

40. Figure 21: Water level history of different African lake .

41. Figure 22 : Sediment accumulation in an idealised, low latitude rift half graben
lake.

42. Formation of Kathmandu lake and sedimentation
Figure 23:Profile showing the formation
of Kathmandu lake and sedimentation due
to tectonics.

43. Figure 24: Different types of lake succession of kathmandu valley .

44. Thank you 
Any queries?