KINGDOM Natural Recources Affairs ETHERLANDS Ministry of JlMi

KINGDOM

Natural Recources Affairs

ETHERLANDS Ministry of JlMieign Affairs

KINGDOM OF THE NETHERLANDS MINISTRY OF FOREIGN AFFAIRS

32'1·t IiYD 1301

-.-~-Yel"ho~en

REPUBLIC OF ZAMBIA

MINISTRY OF WATER AND NATURAL RESOURCES DEPARTMENT OF \VATER AFFAIRS

LUAN I KA WATER\;JAY field survey

July 1978

drecigiilg, enginecrinC' and rnamlgement stu'dies

TABLE OF CONTENTS

1.

Introduction

2. General description of the problem

2.1. Transport of goods & persons 2.2. Waterways

2.3.

Waterlevel differences

2.4.

Maintenance

2.5.

Bottom characteristics.

3.

Mapping, topographical names

4.

Existing waterways

.

4.1.

4.2.

4.3.

4.4.

4.5.

4.6.

Necubela Canal The Little River The Sikolongo Canal The Zambezi River

The Iboka-CanaJ and connecting waterways The Luanginga rive r system

lI.6.1. The lower section of the Luanginga

4.6.2.

The Luanginga near Mapungo School

4.6.3.

The Nasilala Canals

4.6.4.

The Luanginga near Mwanga

4.6.5.

The Namakuyu Canal

4.6.6.

The New Namakuyu Canal

4.6.7.

The junction near Malasha Store

4.6.8.

The Luanginga from Nalisheko to Malasha Store

4.6.9.

The Nalisheko area

4.6.10

Water affairs boat landing

4.6 .. 11

The Boma-Canal

LI.6.12 The Kalabo boat harbour

5. Rural Canals

6.

River Works

7.

8.

9.

6.1.

Sho'rt cut problems

6.2.

Ri ver regul at ions

6.3.

Training works

6.3.1.

Bandall ing

6.3.2.

Cr i bs

6.3.3.

Pi lings

6.3.4.

Stone protections

6.3.5.

Clay protections

6.3.6.

Fascine matrasses Proposed improvements

7.1.

NebClbe I a Cana I

7.2.

Li ttl e Ri ver

7.3.

New S i ko fongo Canal

7.4.

Old Sikolongo Canal

7.S.

The Iboka Cana I

7.6.

The lmver section of the Luanginga

7.7.

The Luanging~ near Mapungo School

7.8,

The Nasilala Canals

7.9.

The Luanginga near Mwanga

7.10

The Namakuyu canals and the junction

7. 11

The Luanginga north of Malasha Store Summary of the proposed improvements Further investigations

9.1.

Information still needed 9.2. Continuous measurements

1. I NTRODUCTI ON

During the dry season shipping between Mongu and Kalabo is impossible, therefore this project was started to improve the situation by dredging. Dredging was started at Mongu harbour, where a new dredger was

delivered, assembled and launched~

Due to the urgency of the project dredging had to be started before a profound survey concerning the topography and hydrography of the total area was made. This is one of the reasons why it was not possible to make a detailed time and production planning.

This report is based on a field survey, carried out from May 29th until June 29th, 1978 by Ir. H.J. Verhagen. The survey can be divided into two parts, first the topographical survey, reSUlting

in a 1:20,000 map of the Luanika-Waterway, and second the

hydrographic and morphological survey. The purpose of the surveys was to give an advice for the planning of the dredging works in

2. GENERAL DESCRIPTION OF THE PROBLEM

2.1. Transport of goods and persons

During the high water'period (approx. from December unti August) road traffic from Mongu to Kalabo is i~possible.

In this period only three ways of transport to Kalabo are possible. 2.

1. By air. Zambia Air runs a regular service (twice a week) to Kalabo. The, airl ine is mainly used for transport of mail,

special goods and persons. Because of the cost of air transport no large increase of this transport is to be expected.

2. By road via Senanga (382 km). The road from Mongu to Senanga (143 km) can be described as IIpart ially improved roadl l, ~"hereas

the 185 km from Senanga to Kalabo is a dirt-road, suitable for

cross-cou~try vehicles.

3. By barge. The waterway from Mongu to Kalabo fol lows natural rivers, improved rivers and artificial canals. The depth of this waterway is insufficient, especially in the low water season. Some stretches even dry from August until October.

It has been decided to improve the waterway in such a way that ship traffic is possible throughout the year.

At the moment five types of vessels can be distinguished.

1. Motorised barges with a capacity of about 25 tons. Three barges are in service at the moment. The draught of these barges is about m. The total transport capacity of these barges 2 x 3 x 25

=

150 tons/week.

3.

2. Banana-boats, Banana shaped vessels with an outboard engine. Their capacity is approx. ton. They are used mainly for

tran~port of persons.

Banana boats are usually overloaded (sometimes 25 persons are in one boat), while the moto~ dapacity of the outboard engine is too small. The freeboard of these boats is often less than 20 cm. The total transport capacity is about

7

x 5 x 1

=

35 tons/week.

3.

Peddle-barges, also having a ~apacity of 1 ton, but propelled by 6 rowers with paddles. It takes four days to reach Kalabo with these barges. The total transport capacity is unknown, but

tons

expected to be about 15 /week.

4.

Speed-boats with a capacity of

4-6

persons, mostly used by officials and leading merchants for quick communication. The transport-capacity of the speed-boats is negl igible.

5. Canoes are used by local people for transport between the villages and for fisheries. These canoes are very shallow, and are mostly

used outside the waterway. Their transport capacity is negligible.

The smaller boats (banana boat, peddle barge and canoe) are hampered considerably by waves from speedboats and motorised barges, and also by wind waves .in open water. On the Zambezi and in the mouth of the Luanginga River waves up to 50 cm occur regularly. These waves are very dangerous for the overloaded banana-boats. With these boats many accidents occur, even fatal ones.

2.2. Wa.terways..

The Luanika waterway is indicated in fig. 1.

During high water ships can use the Iboka-Canal as well as the S.ikolongo-Canal. The way through the Sfkolongo-canal is as long as the Iboka route, but the Iboka-route is preferred, because on this route it is not necessary to navigate the Zambezi over a long distance.

4.

-;r:·'9ur<2. '"'.

(se.e. o\.SC) lhe.. 1:'2.'=iD£>DD CO"'.l 0+

5.

Because the Iboka-Canal is more shallow than the Sikolongo-route, the bigger ships can pass the Iboka-Canal only during a short period. Small canoes can use the Iboka-Canal nearly throughout the whole year; although some places are dry during extreme low water.

From the Zambezi up to Kalabo only one waterway exists, following the Luanginga River.

2.3.

Waterlevels

The Zambezi is a river entirely fed by rainwater. The rain is fall ing during a few months, between October and March. During this period the waterlevel rises considerably (up to

7

m). This waterlevel rise is caused

by the fact that the discharge capacity of the Zambezi near the Victoria Falls is rather low. After the rainy-season the waterlevel will fall.

several flats

r7»h-/~

Ka I abo

r

-0

7--,--

I ' / / ' . ' . ,I>' t' , / / ' Zambez i ba sin , " ' . / /

~----Li__ ",t- fl" .¢!S:' '" groundwater seepage

figure 2:

During this period the river is fed by seepage from the flats east of the river. Because the bottom consists of permeable sand, the

groundwater wil I flow to the river.

The \1aterlevel is measured in this area at three places: at Matongo Barge Station, near 5ikolongo and near Kalabo. Onfortunately the height of the level-zero above National Datum is only known for Matongo

(3313.18

feet).

6.

In order to allow comparison of the waterlevels it has been assumed that ,during high water the water level at Matbngo is equal to the water level

at Sikolongo. (So the current in the little River is approx. zero). The consequence of this assumption is that during low water the water

level of Matongo is 1.5 m lower than at Sikolongo, resulting in a slope of approx. 10-

4,

which is a normal figure for rivers.

A similar assumption for the Kalabo-scale is not possible, but in order to allow comparison of the levels, 'the Kalabo data are shifted uhti I a value in the same range.

The results of these procedures are presented in fig.

3.

From these figures it may be concluded that during low water the velocity in the Little River has a considerable value. In the Iboka-Canal the velocity will be, zero, because some parts of this canal are dry in the low water period.

In the Luanginga the velocity will also be low ~ecausethe di~charge is nearly zero. (see fig.

4).

2.4. Maintenance

Because the river is a dynamic feature, channels are changing continuously. These changes are caused by erosion and sedimentation. For navigational use sedimentation causes the biggest problem.

Since it is not always possible to prevent sedimentation of the navigation channels in rivers and of the canals they have to be main-tained.

~----':).t

f

;@'IJ'"fO).f:1 It , ... f!.) c

\tk~l::£rle:\n811s

I

f

I

I

I

_@

I

1

I

\

_,11

\

\

\

\

\e

<\

C\

&

\

\

(> \ iii

\

1'1

[\

\@

:~.

9 \ <>

\

"

>-'\.

0"~

1"-G

"

~ I\>

"-~

""-"

8

_·

0 (t) 0 0 I;) t

o

o {\J

o

Fj - t, -~

o

Q \ - - -_\(1

o

--1--.---

l-~

~ ---~~~--r'Ei>

'o@

<,> !

,

I

... ' " ""''<., ---.--~"''']-o o o 0 0

o

0 0 ttl 'l' cO ~2~iohal-r-d=ts'I\,'-I 'Fl~ure!i

XlI SCHARGE AT i<AL~J3,O

o

o

C\-i

o

o

.,..

o

_o

-,.-,

-9.

2.5. Bottom charocteristics

The bottom of the flood-plain consists mainly of fine sand and clay. The fine sand is densely packed. This is caused by the yearly variations

in the waterlevel. Therefore, dredging this sand makes use of a cutter head. In fig.

5

the sieve-curves of several sand sa~ples are given.

It is clear that the sand is nearly identical allover the plain.

The clay is very fine, and is therefore difficult to dredge. Th1s clay can be used very weI I for protection works. The distribution of

the clay is given in fig.

6.

Only near the small village halfway the Nebubela Canal S0me hard rocks were found. This is amorphe sedimentary rock, which consists mainly of silicium. From the r~r.all samples no more detailed information can be obtained. For further information a stratigraphic investigation (with boreholes) is necessary. This is an expensive' investigation which is not.advised.

18 995 99 % - - --t== - - - - + - - - L _ 95 90 85 ---===--~--~"

-70 65 ~-~ -=-_ ---60 55 50 ________ 0_-- - - - -.... -=-- ---40 35 30 25 20 15 10 - ; - - - ; - - / , 'r-I .,

-::::::::::::---1'.---7--01 1000 900 BOO 700 600 500 0.5 i 400 ~5 I 350 1.5 50 60 300 250 70 eo 200 25 100 120 140 170 230 __ l ___ . _ _ ,_ 150 100 90 90 70 60 I 3.5 270 I ! 50 50 325 400 ~O 20 15 ₁₀ L il: ----~---~--- -- -- --

==:::

-.... - - -

--

-.----~---

-

~'-

---=

-==t=--_{___} L---~ --.--.{~--+-=--==-~=-:~----'-- - - - _' -55 65 75 95

3

j

0.1

ERWAY

\ - - - - -_~ I GRAIN_SIZE DtSTR.lEIUTION hyOROno.mlG SAND_CLA'J sliedreche holland ,0 pm L 5 % 95 90 - - - -! as 80 75 , 70 --- 65 ._---, 60 55 50 (5 40 35 30 25 20 --~--, 15 10 - ---I

3.

MAPPING & _.. TOPOGRAPHICAL NAMES _{_....}

.---Available was a 1 :250.000 topographical map of the area (from 1966) and a blue printed sketch of the Lower Luanginga, scale approx 1:75.000 and from an unknown date.

The topographical map is based on aerial pictures 1 :80.000 and apparently it has not been checked in the field, whereas the map of

the Lower Luanginga has only been made by visual observations. These maps were not suitable for this survey, and therefore a new map has been made 1 :20.000 of the Luanika-Waterway. This map

(in two sheets) is added to this report. The basi~ of this map is formed by 1:40.000 aerial pictures (of 1960). The whole map has been checked in the field and changes in topography since 1960 have been processed.

Topographical names used on these maps are the names locally used. In some cases several names are used for one object. In this report only the names mentioned on the maps are used.

The name Luanika-Waterway however, requires some more explanation. Some people use the name Luanika-canal as an alternative name for the Nebubela canal, while other people, using the name

Luanika-canal, refer to the whole waterway from Mongu up. to Kalabo. In .this report only for the canal from Mongu to the Little River the name Nebubela-Canal is used while the whole waterway (from Mongu to Kalabo) is called Luanika-Waterway.

In this waterway two routes can be distinguished, viz: the Sikolongo route (Nebubela-canal, Little River, Sikolongo-Canal and the Zambezi south of Liyoyelo) and the Iboka-route

(Nebubela-Canal, Little River, Iboka-Canal, Sekel i-Canal, Little River and Zambezi north of Liyoyelo).

4. EXISTING WATERWAY

4.1. The Nebubela eanal

The Nebubela Canal from Mongu to the Little River has a length of about 6.5 km, and is, in general, s~allow. For a map of this canal see Annex 1, for the profile fig

7.

Dredging operations started in this canal near,Mongu with an extension of the existing harbour. Dredging has continued unti I now over a distance of about 2 km from the harbour.

From aeri~l pictures it may be concluded that the easterly part of the canal fol lows an old riverbed. At several places in this

13.

part of the canal the bottom consists of clay. 'In the middle section, just east of the first inhabited earth-heaps mostly sand can be

expected. The ~arth-heaps themselves are composed of sand, clay and stones whtch were removed from the canal-bottom by means of drag-l ines

during previous improvements. From aerial pictures it can be expected that this hard layer has a width of about 300 m. Because the thickness of

the layer is un-known, it is not possible to predict whether this layer will hamper the dredging operations or not.

If the hard layer is not very thick, this laye~ has perhaps already been removed totally by previous operations.

During the survey period the waterlevel was rather high, so that is was not possible to Investigate this IDcatlon thouroughly. West of this hard layer the canal has a reasonable depth, not very much dredging seems to be necessary. Here the canal follows again an old river bed, so that clay may be expected.

Only near an old shortcut the depth is less. The last 1500 m of the canal have been excavated. 'Here old sandy clay may be expected. At the mouth of Nebube I a cana I a shoa 1 is formed.

@)

r~

b

~1

H

.u ~ J ~ 0 Ij -.j _...

ll'

®

"U :l £:

~I

f\

,----;---I

I

I

,

I

I

I

I

*

:i j S

III

fictur~~

:r

tt;~ 14,

@

_.J m c co U 0

~

0 ~ Cil 'N

I

~I

(0

I

N@

f o

~I

II

F'n:?'t.:(Q. qiOI)"l HbntiyJ A:.:::> ./;:;\)e. L"8l!YlbCl'tz..i

15.

It is expected that thls shoal is rebuilt every y~ar by the currents. During high water, the current in Nebubela canal has a different

direction at the east-side of the canal. This is caused by the fact that the Nebubela canal is crossed by a flood-channel of the Zambezi River.

'",,.to Kalabo ~Matongo

\

figure

8:

/

II

high water bed

~ to the Zambez i

This flood-channel drains the total area North of Mongu (including the Luena Flats), and ends in the Little River, 12 km south of the Nebubela Canal.

.,

-It is clear that the plain directly south of_ the Nebubela Canal does not drain on the canal, but in a compl icated way, directly on the Lit tIe Rive r •

16.

4.2.

The Little River

The Little River is a natural river, it is a small branch of the Zambezi an~ follows an old riverbed of the Zambezl4 Although it Is fed directly from the Zambezi, it gets most of its water in the high water season through the plain. This water enters from the

Zambezi between Lukulu and Kabeti, and comes also from the Luena Flats. When the water is fall ing the Little River drains this flood water.

Because the Little River is a natural river, it meanders

somewhat. In the area where the Little River is used as a waterway these meanders don't generally cause problems. Two meanders have been succesfully cut short durinq previous dredgin0 operations. Two smaller shortcuts, made in the past were not as succesfull as expected.

Two bends in the Misika-area may have to be cut short in the near future.

high ""ater bed rroo _ _ -IA~ _ _ ....,'l

t

---T

----i-l---\- -c----\

'-r~

low water bed figure 9:

A detailed investigation was not possible, because the time available was not sufficient for that purpose. Since during this survey-period

the water-level was rather high, the river fol lowed its high water bed. By making only depth soundings In the middle (x), tfle rea I depth of the nav I gat ion channel is not meas u red. The on I y ".fay to find

the rea 1 depth' Is mak i ng cross-sect ions (---) Because making cross-sections is very time consuming, it could not be done in this short period. Therefore the Little River should be surveyed -in greater detAil during the low water period.

4.3. The Sikolongo Canal

The Sikolongo Canal consist of two parts; the old canal from the Little River to the Zambezi, and the new cut from the Hisika area, straight to the Sikolongo Canal. The bottomlevel of the Sikolongo-canal is in general low enough to guarantee shipping throughout the year. In the new cut, however, near the connection with the old canal some shal low places exist. These shallow places are caused by the fact that the banks exists of fine sand, Which flows back into the channel. In this way a wide shallow channeLarises. The velocity at this point is rather low, so that siltation will occur at this place. figure 10 Sikolongo Canal to·the Zambezi steep

bank sandy bank

sandy bank

The water comes through the old Sikolongo Canal .. At the junction the water flows with considerable speed aqainst a steep bank

17.

of consistent sandy clay. This bank is eroded. Then most of the water flows away in turbulent eddies to the New Sikolongo Canal. This

water contains a lot of sediment from the eroded b~nk.;Aftertwenty

meters the banks of the New Sikolongo Canalconiist of fine~sanda

creating a wide shallow channel, as ex~lained above. The sediment in the water will settle here and cause a shoal. Only at the southern side of the shoal a small navigation channel exists.

The amount of water flowing into the Northern section of the old 5 i ko 1 ongo Cana 1 is neg 1 i 9 i b 1 e.

Another small shallow spot can be found near the_junction of the 5ikolongo Canal and the Zambezi. No special explanation can be given for this shoal. It is assumed that this shoal is simply caused by settlement of sediment from the Zambezi.

4.4. The Zambezi-river

The Zambezi-river is in general wide and of sufficient depth for

18.

shipping. However, the channels of the river have to be followed carefully, when navigating with deep draught ships, because there are many

shoals in the riverbed. Navigation may be problematic, because the Zambezi contains much suspended sediment. Due to this suspended load it is difficult to distinguish the underwater shoals.

As already indicated in the former chapter, the main problem regarding the Zambezi-river is the occurrance of relative high waves, which are very dangerous for.small boats.

4.5. The Iboka-canal and conn..ecting waterway.-2.

Local people prefer the Iboka canal to the 5ikolongo canal. Their main argument is that the Iboka-route is much shorter than the 5ikolongo-route. The difference is, however, only

2.5

km. But navigating these two stretches gives the impression that the Iboka-canal is much shorter. This can be explained by the fact that,

following the 5ikolongo-traject one has to sai 1 14 km on the Zambezi, while fol lowing the Iboka-route, one has to pass only 3 km on the

Zambezi. And because canoeing on the Zambezi is very difficult and dangerous most people prefer the small canals. The freeboard

of a paddle-canoe is only 10 em, the freeboard of a bananaboat varies from 10 to 30 cm.

Waves of

50

cm occur regularly on the Zambezi. 50 it is clear that these boats avoid the Zambezi.

----~

In general the Iboka waterway is very narrow, in some stretches the width is only 5 m, and the canal is very shallow. During the dry season some spots even dry. Transport barges use this canal from January up to July, speed-boats can use it a few months longer. The canal can be divided into several sections:

19.

a. A former lake from the Little River straight north. This lake has a reasonable depth, only some shoals occur.

b. The Iboka-canal, from the lake just mentioned to the Lealui-lake. This section is about 10 m wide, and has a depth varying from 0-1.5 m during the low water period. In this section is a

crossing with the road from Mongu to Kalabo. This point is very shallow and becomes dry during the low water reriod.

c. The Lealui-lake, which is of sufficient depth.

d. The northern section of the Iboka-canal. With the exception of the junction with the Lealui Lake, this canal is sufficiently deep.

e. The Rural Council Shortcut. The junction of the Iboka-canal and the Sekel i-canal were very narrow and shallow.

Therefore the Mongu Rural Council, has made a shortcut of about 200 m, and a width of about 5 m. This shortcut is not deep,

it will become nearly dry. The cut was made in 1977 during the low water period and was dug by hand.

f. The Sekel i-canal is also very narrow, but has a considerable depth. Because of the fast current no sedimentation occurs in the canal. The canal is fed with sediment laden water from the Zambezi. This sand does not settle in the western section of the canal, because of the current. In the middle of the Canal

is a small lake. In this lake the velocity is low, the sediment settles, and a shoal is formed. In the eastern section of the canal no sand is transported, the water is very clear.

g. Little Rivet", not causing any problems.

- - - ' "

I

A special problem occurs at the beginning of the Iboka-canal, approximately 2 km north of the junction with the Little River. There the waterway

is totally overgrown with reed, which causes navigational problems, even during the high water season.

20.

The lower Luanginga river (from Kalabo to the Zambezi) can be divided into two sections: an upper-section from Kalabo to the Mapungo School, and a lower section from the Mapungo school to the Zambezi.

The waterlevel of the Luanginga is only measured at the level gauge at Kalabo-Boma, at the upper side of the Boma-canal. This Hydrological

station exists already many years~ From this station a waterlevel-discharge curve is available. This curve is given in fig. If*. The'variation

of waterlevels in the course of a year is presented in fig.

3.

The variation in the waterlevel shows that the influence of the

Zambezi on the level of the upper section of the Luanginga

is small. Especial l~ the rise of the water is more quickly in the Luanginga than in the Zambezi. This is caused by the fact that the watershed of ' the Luanginga is smaller than the Zambezi watershed.

Because of this independence from the Zambezi, the upper section of the lower Luanginga may be considered as a typical river. Its lower section has rather the character of a fJood-channel of the Zambezi, because it

is mainly fed by floodwater from the Zambezi. This floodwater is drained from the floodplain by the lower section of the Luambimba. See fig nr

In the lower section of the Luanginga no waterlevels are measured, so one cannot determine exactly the maximum and minimum levels; they have to be estimated from the variations in waterlevels measured at Kalabo and Sikolongo. More detai led measurements over a longer period seem to be advisable. This will be discussed in more detail in chapter 9.2

*Normally a water level discharge curve shows a hysteresis-loop, caused by the differences during the rise and fall of the water. Because it

is not known whether the measurements were made during rising or 'fall ing water, this loop could not be indicated.

In general the water of the Luanginga is very clear. One can see bottom very clearly down to

4

m. All the transport in the

21.

Luanginga has to be bed-load transport. Because no bed-load measurements were carried out in the past (the hydro-section of the Western Province has only a suspended sediment sampler) the amount of sediment trans-ported by the river is not known.

Calculation of this transport is useless without the possibility to calibrate the parameters of the formulae. This is du~ to the fact that the discharge varies too much d~ring a year, and because of the large fields of weed bordering the river.

Another aspect rega~ding sediment transport is that all the formulae have been developed for alluvial rivers, i.e. rivers flowing in their own sediment, and able to transport as much sediment as they can

transport theoretically.

Large sections of the Luanginga, however, consist of hard clay. This clay is pot eroded very much, and sand is transported over this clay. Because of the clearness of the water, this can be observed eas i ly.

At the confluence of Luanginga and Zambezi the difference in sediment concentration can be seen clearly. A sharp 1 ine shows the exact location of the confluence.

In general the lower section is deep. A few channels and shortcuts have been mad~ most of them with considerable success. Hardly any maintenance is required. The wide waters ~etween the Zambezi and the Mbalala Canal, and between the Mbalala Canal and Sifuluti, however, are dangerous for small boats (banana boats, peddle barges):

Because of the depth, high waves occur regularly. Only at a few spots shal low areas have been measured. This may be caused, however, by the fact that the measurements were made during high water, and the navigation channel could not be seen.

~---- ~

I I

22.

In some parts (near Mvvandi and in the Namango Canal) extensive growth of weed tends to tlose the navigation channel.

In the Nasilele Canal a shallow spot exists because here most of the water flows through the main ri ver. Deepening the cana I, and pa rt I y closing river wi II improve the situation for a long time.

Then no maintenance can be expected in the near future.

North of the confluence of Luanginga and Luambimba, the discharge is considerably less. This, in combination with the fact that the bank near Mapungo-school consists of sand, causes a very shallow river. Near the Mapungo b0~t landing, the river is very wide. Because of this width, velocity is very low, and the river ~iltates. This area will nearly dry during the low water period. Two short cuts were made near Hart's Store. These short-cuts are also very shallow, mainly because much water is strll flowirtCJ through the original river.

The banks in the west-side of. the river are very steep and consi~t

of sand. Because the bank is eroded sand wi 11 come into the river, and will cause siltation at those spots where the transport capacity of the river decreas~s.

This problem not only occurs near Mapungo school, but also along other sections of the river. These sections are indicated as accurate as

possible on the map of the Luanginga, VJhich is added to this report.

4.6.3. The NasiZaZa CanaZs

These canals are the shallmvest parts of the Luanginga. The main river, parallel to the Canals is non-navigable.

the

The si ltation in these canals seems to be caused by a considerable loss of water to the swamp, east of the canal. Many gaps in the east border can be observed, through which the water is flowing out of the canal

at considerable speed. Dut to this loss of water, the velocity will decrease, and the sediment-burden of the river will settle.

Since bank erosion occurs at many places north 6f the Naslla Canals the river is heavily .Ioaded with sediment, so even a small decrease

in sediment transport capacity will cause erosion.

23.

Here the situation is somewhat better than in the Nasilala Canals,

because more water is flowing through the river, however, because of the heavy bank erosion at the escarpment, a lot of sand is fed to the

river, causing much si Itation.

In the present situation this is no canal, because nearly all the water of the Luanginga is flowing through it. The original Luanginga east of the canal is totally closed. Only some water is lost through a

separate branch to the Luambimba river. Because no bank· erosion occurs along the bank of the Namakuyu Canal, the situjtion is better than

in the downstream river-section near Mwanga.

It is not understood why this canal has been dug, because the old

Namakuyu Canal is very well navigable. The New Namakuyu Canal was excavated through clay-layers. Observations indicate that in this canal hardly any ·erosion or sedimentation occurs. Only at the begin of the canal·

there are some shoals. A relatJvely thin layer of sand is transported over the bottom of the canal. The design depth of this canal, however, is

totally insufficient. The canal will nearly becomes dry during the low water season.

figure 11 Luanginga L.L. connection

/'

IOld Namakuyu Canal

-"

?'!-'"---New Namakuyu Canal

~/I~hI;'!it,/j;~r'II\\\;\\\\~'\\\~

I!J Malasha store

The flow-pattern near Malasha Store is rather compl icated due to the number of different waterways

in that area. Most of the water coming from NW through the

Luanginga, follows that river along Malasha store, and flows into the Old Namakuyu Canal. Near Malasha store the banks are eroded. Some water flows through the Malasha short-cut to the junction with the New Namakuyu canal.

It is clear that at that junction a very turbulent flow pattern exists. Due to this turbulence, the bottom has eroded substantial. Immediately

after the junction the flow pattern ,is quite normal, and the sand, just stirred up, will settle. In the Ne\,;/ as well 'as in the Old Namakuyu Canal these shoals can be found.

Just downstream the shoal in the Hew Namakuyu Canal is a bifurcation. Here some water is withdrawn from the Luanginga to the Luambimba. Just upstream the Malasha short-cut also some water is withdrawn to this connection.

When this survey was made the water was flowinG fr6m the

Luanginga to the Luambimba. The current in this connection has not necessarily the same direction fhroughout the whole year.

The direction depends on the differences in water level between Luanginga and Luambimba. These differences are not known at this moment, and should be investigated in due course.

The .Malasha short-cut itself is too shallow for normal shipping during a considerable part of the year. This short-cut was not excavated

in the prope~ way. Here the bottom consists cif clay, like the New Namakuyu Canal, and also a thin layer of sand is transported across it.

But in this canal the separate holes, which are dug out during construction can be seen. The remaining parts are not eroded. In fact this canal has no normal profile, it is only a row of excavated craters.

25.

Thfs section of the river has a reasonable navigability, the depth at low water varies from 75 to 150 cm~ but ~lso in this section these

figures are based on a few soundings during highw~ter, and it is,

ther~fore, possible. that the measurements were made outside

the channel. From this section up to Kalabo aerial pictures on a scale 1:12500 are available. These pictures clearly show the structure of the river bottom. In this. section only few sand-ripples occur;

which indicates that not very much sand is passing this section. Most of the sand coming from upstreams is trapped near the Nalisheko canal, and

because no significant erosion takes place in this section, hardly any siltation occurs:

4.6.9. The Nalisheko-area

The Nal isheko Canal is made in such a way that most water of the

Luanginga flows through this canal, while a great deal of the sediment follows the original river. This causes high river dunes in the remaining

river, which become totally dry during the low water season. In the Nalisheko Canal itself no sedimentation occurs

26.

75-Canal

sand

At the end of the canal, just inside the old river-bend there are

some snoa Is, but these shoa I s. do not cause prob I ems, because the. adj acent channel is of sufficient depth.

North-west of the canal a short-cut has been made. Since it was not of sufficient depth and it was made in the siltating side of the river bend, no natural scouring occurs. This shortcut will

siltate totally . . Because the river itself is sufficiently deep, the siltation of the short-cut will not cause any problems.

BetweenNal isheko and water-Affairs boat,landinq the river is deep enough. Only some shore erosion occurs, which may give problems downstreams.

Water-AHa irs Off i ce \ \

'

.... figure 13

4.6.11. The Borna Canal

27.

Because of ~he river-bend, the main current passes just below the escarpment. This current strongly erodes the steep

escarpment, and endun~ers the bouses on the enscarpment. The boat

landing itself is lying at the deep channel, which also allows deep-druught ships to reach the

bank. Loading and unloading however, is hampered by the steep slope.

The Boma Canal has partly si lted up and some sections are totally, overgrown with weeds and bushes. The canal is'only navi~able for canoes and small boats. Even speed-boats have difficulties on this canal. The river, east of the canal Is very well navigable.

{}. 6. 12. 'l'he Ka labo boat harbour

The "hat-bour" of Kalabo Is nowadays a simple boat-landing without any facll itjes. The slope of this boat-landing is rather flat, so that

loading and unloading of barges may cause problems. Crane faci lities are not available.

Both the river and the canal transport sediment into the Kaiabo lagoon. The current in the lagoon is nearly zero, and therefore

28.

all the sediment settles in front of the mouth of the river,

respectively the canal. These sand-tongues can be observed clearly. Because of this sand-trap effect of the Kalabo lagoo~ not very much sand is transported from the upper Luanginga to the lower Luanginga, which might be advantageous where ~he planning of riv~r-works

is concerned.

'

29.

5. RURAL CANALS

Besides the canals mentioned in the preceeding chapter, a large number of small canals and ditches exist in the area. These small canals were made for local transport with canoes. Because, even during the

low water season, land transport through the plain is difficult or even impossible, the provisioning of the villages is done by canoes. To allow the passage of these canoes also in the dry period these smal I canals were duq, mostly be hand.

These canals are maintained under responsibi IJty of the

Rural Council of t-longu in Limulunga. The financing of the maintenance

is diffic~lt. Maintenance is therefore mostly carried out in

self-help programmes.

Because the existence of the rural canals is vital to a considerable part of the population, an inventarisation of these canals should be considered.

Also a close cooperation between the Director of Works of the Rural Council, and the responsible engineer of Water Affairs Mongu

is therefore advisable. Especially the coordination of maintenance works is very important.

30.

6. RIVER WORKS

6.1. Short-cut problems

Most short-cuts in the Mongu-Ka1abo waterway are causing difficulties. There are also. new plans forshort-cuts. Before takino the decision' to make a shortcut, hO\"lever; sever;)raspects have to be studied.

Initial costs

---First the amount of cubic meters to be dredged for both the short-cut and a normal river improvement has to be calculated.

"

_"

,

'\ \ '\ '\ \ \ \ \

\

\

\ \ \ short-cut\ \ \ \

original Example: Original length 450 m, length of the

\ \ \ \ river

.

\ \

short-cut 300 m. Original depth 3 m, required depth 5 m. Original width 15 m, required width 20 m.

For the improvement: Amount to be dre~ged

3 .

450 x 2 x 15 + 450 x 5 x 5

=

24800 m Weed-covered area to be removed

450 x 5

=

2250 m2

\

For the short-cut Amount to be dredged 300 x 20 x 5

=

30000 m3

figure 14 Weed covered area to be removed 300 x 20

=

6000 m2

Estimated prices

*)

dredging 0.15

K/m3~

weed removing 0.05 K/m2 So cost of the improvement 24800 x 0.15 + 2250 )( 0.05:~ If 000 K cost of the short-cut 30000 x 0.15 + 6000 x 0.05'~ 4800 K

Remark: The prices mentioned in this chapter are based on operational cost only. Depreciation of the investments, the cost of maintenance, administrative staff and foreign consultants are not included.

Maintenance cost

---Suppose every year an accretion of 0.1 m occurs (which is extremely high), then the maintenance costs are:

for the improvement 450 x 20 x 0.1 = 900 m3

~

125 K for the short-cuts 300 x 20 x 0.1 = 600 m3

'.~

85 K

,.

31.

In a river a natural bAlance exists between the velocity of the water and the depth (and some 6ther parameters, which are not of interest now). When a short-cut is made, the total area avai lable for the water will increase, and thus the velocity will decrease. \vhen the velocity decreases, also the depth decreases. Even with small differences in water velocity, the depth wi 11 vary very much, because the

sand-transport{S) is related to the velocity (v) by a power law.

S

=

Av6

In which A is a constant of the river. It is therefore, necessary to·close the original river to ensure sufficient depth. This closing will cost also some money, but not very much, because the sand dredged from the

short-cut can be used. In that case the closing costs can be estimated at about 500 K.

A natural river is a dynamic feature.· .If a river is not regulated with technical means 1 ike cribs, revetments, etc. it will make its own way. Short-cuts are a disturbance in this natural pattern. The exact

prediction of the rivers behaviour after such an operation is extrem~ly

difficult. Only some general features can be predi~ted. By way of example the connection of the Nebubela Canal with the Little River wi 11 be discussed.

to Kalabo

Nebulela

figure 15

Due to this difference an eddy is formed in the mouth of the Nebubela Canal. This eddy causes a shoal. It is very alluring to make a short-cut as indicated.

32.

But when this short-cut is made, most of the water wi 11 be forced into the Nebubela Canal, and

create problems at the point were the short-Mongu cut enters the Nebubela Canal

Because the length of the waterway is decreased by a short-cut, people wi 11 arrive somewhat earl ier at their destination.

But such an operational profit is mostly negligible, regarding the situation in Zambia (the distance from Mongu to the Zambezi is measured along the canals 22 km. A straight 1 ine is 18 km).

A number of the existing short-cuts are siltating; some of them only at the beginning, or at the end, whereas others are siltating over the whole distance. Many of these si ltafion problems arose because these short-cuts were

made without any hydrographical and morphological study. Some of these problems can be solved by maintenance dredging, others by closing non-used rive,- branches, or by other river regulation works.

Unfortunate 1 y, some prob 1 ems cannot be so 1 ved at all. I n those cases the best solution is to abandon the canal, and improve the adjacent river. Generally. speaking, the problems east of the Zambezi can be sorved by maintenance, and west of the river by means of river-regulation works. This will be discussed in the next chapters.

Conclusion

In most cases new short-cuts will be uneconomic, especially regarding the uncertainties in the stabi lity of the short-cut. Only in exceptional cases short-cuts may be considered, but is advisable to study all the aspects of such a short-cut thoroughly.

In case of the existing short-cuts, more detailed study \",ill indicate ho\", t.he p,-ob 1 ems can be so 1 ved.

r

_33.

6.2. River r.egulations

I

:::::;:.::;~:

I

s hoa 1

~erosion

figure 16

One of the types of rivers is the meander-river. The rivers and flood channels in the Zambezi-basin are nearly all of this type.

Characteristic of this type are the eroding river-bends.

In due course these bends will become longer, and at a given moment a

natural short-cut wi I I arise, while

~ the remainders of the former river

~

can be found on maps as "horse-shoe lakes".

In nature this process is disturbed bY'many things in bottom topography, like high grounds, hard layers, etc. T~e result is a very whiMsical pattern. Normal navigation in this kind of river may cause some problems because of the shoals between the bends. To improve this the river could

be regulated. This means that special works are made to force the river into a preselected bed, preventing erosion and sedimentation.

Such a complete regulation is very expensive, and therefore not advis'

~ble for the Luanika-waterway. But in certain sections the river

could be improved b~ r~gulation works, only cove~in~ short distances.

By planning such regulation works it should be real ised.that making a straight river is impossible. The regulated river has to have gentle bends ..

The distance between the bends depends on the discharge and the

river-slope. Calculation of the distance is not exactly possible, there-fore the distance between bends in the unregulated river should be appl ied.

The banks of the river have to be protected with training works. 1 ike cribs, mattresses, etc. They will be discussed in the next section.

34.

6.3.

Training works

This method is generally used in S.E. Asia.

The principle of this system is the concentration of the discharge

in the channel, which has to be deep~nedout. Bandalls increase the sand transport capacity and within a few weeks the necessary scouring will take place. The concentration of discharge is achieved by placing screens

along the channel, increasing the resistance in that location. Moreover, the water is directed to the channel.

---.' :'./: bandalls·, ,,;",''-':'''''', _ ' " t ' ~.". \ ' , .~~., • • ' • • • • • ...::..,.~" • • • • • • ' ...

figure 17

cross-section bandal1

Bandal Is were originally made from bamboo-stakes with wattle-work (made of, reed) .

During the fall of the water the wattle-work is shifted down; the water flows under the bandall, and scours the bottom.

Behind the bandall sand will settle. So a channel and a threshold develops. The water is dir'ected through the channel towards the main-channel, giving the desi red flow-concentration.

This solution is therefore only possible in river-sections where shal low shoals neighbour the flow channels. The quantity of water flowing

accross the shoal must be such that.enbugh water is available to scour out the main channel.

The water should not fall too fast, so that sufficient time is avai lable to' cause the desired scouring.

35.

This solution is very cheap, requires only unskil led labour.

Therefore bandall ing may be advised for some sections in the Luanginga (near Mapungo school, Nasilala Canals) and the Little River.

6.3.2. Cribs

figure 18

Cribs are stone constructions made In rivers to prevent scouring of the bank. This scouring Is prevented by concentrating the main current into the channel.

Cribs can be made from heavy stones or from gabions. Gablons are wired boxes filled with various types of st~nes (quarry-run).

In general cribs are very good means for river training. They are, however, rather expensive, especially Jf stones are not easily available.

For this reason crjbs cannot be advised at this moment, but'may be used at a later stage.

36.

Instead of stone-cribs sometimes rows of piles are used. These piles al low some passage of water, but they have such a resistance that behind the pi 1 ing no sand transport will occur. Then all the sand wi 11 settle, and therefore the protected bank will not erode.

H;\-!.

; 7

L. \./.

protection new bottem

The I ife-time of these pil ings is rather short. They can be appl ied when enough wood and reed is available. They have to be maintained

regularly.

Pi I ings can be advised at those spots where at a later stage a stone crib is planned.

figure 20

37.

One of the better ways to protect slopes is the construction of a stone-protection. The stone can be tipped at random or placed in order.

Also a concrete or asphalt protection can be used. But because neither stones, nor concrete, nor asphalt is easily available, none of these solutions can be advised.

-~-~

~ ~ ~

I

38.

A clay-protection of slopes is one of the cheapest ways to protect slopes. Because enough clay is available, this protection-method should be appl ied as much as possible

in the Luanika-waterway area.

Clay should be placed on the sand with drag-l ines figure 21 or grab cranes. A skilled operator can make

clay layers with a minimum thickness of about 30 cm. The clay will erode very slowly. This slow erosion can be prevented by planting grass on the clay. This grass-layer has to be maintained carefully.

6.3.6. Fascine Mattresses

For the prevention of erosion of underwater-slopes, low dams, etc. fascine mattresses are the best and cheapest methdd. The construction of these mattresses, made of thin wood and reed, is quite simple, and can be done by unskilled labourers, trained for this job.

It should, however, be done under supervision of an expert in mattress-construction.

\

39.

7.

PROPOSED IMPROVEMENTS

7.1. Nebubela Canal

In fig.

7

the profile from Mongu to the Zambezi is presented. From this figure it is clear that especially in the Nebubela Canal two sections have to be dredged.

1. From the dredger as far as the small village 2. Two points at the end of the canal.

Because in these places the bottom is above the low water level, dred-ging is most urgent.

To prevent future siltation it is proposed to close the gaps in the southern bank of the canal. When these gaps are closed, the flood~ channel Is closed, and all the water from the Luena flats is drained

through the Nebubela Canal. Then, the discharge in the canal will increase, and consequently also the velocity. And due to this increased velocity the sand-transport capacity Is increased, and the si ltation will

decrease.

The gaps can be closed by making a sand dam along the southern side of the canal, with a height equal to the flood-level. This can easily

be done with the sand reclaimed from the canal. Especially near

(

the location where nowadays the water enters the plains, this has to be done with care.

Also the so-cal led "drainage canal" just off Mongu should be closed. This ditch is no dl-ainage canal at all, the water ,is generally flowing

from the canal into the ditch. Also this part of the plain drains to

The water level difference between both sides of the dike, will be only a few em, but that is enough to cause a considerable current

in the cana I.

40.

This sand-dam has to be protected against waves by boats. This can be done in the best way with a clay-protection. Clay deposits are ample avai lable near the Nebubela Canal.

The shoal at the end of the canal will be removed naturally. However, in some years the shoal will not disapear totally and some maintenance might be necessarYr

7.2. Little River

In the Little River a few shallow spots have been indentified, but as already is indicated in chapter 4.2., this does not necessaGily mean that this is the deepest point. To be sure about this, first the channel should be local ised.

When the channel has been localised primary improvements with bandalls may be recommended.

At three points short-cuts could be made (1,11,111, see map). The short-cuts I and I I are expensive and not economical at all at this moment.

Short-cut I I I has already been made, but is too shallow at this moment. Improvement of this short-cut, combined with a closing of the remaining river should be recommended for a later stage.

When this short-cut is made, the new river-banks should be protected with clay.

7.3.

New Sikolongo Canal

figure 22

7.4. Old Sikolongo Canal

41.

The only problem occurs at the junction with the old Sikolongo canal. The best

solution seems to be the construction of a regulated river bend. The connection to the north sh~uld be closed and a

gentle curve should be created. The sandy bank (a) has to be

pro-tected either with a clay-protection, eventual combined with fascine mattresses, or

old northern connection can be made with pilings, or also with clay and

fascine,mattresses. Because of the bend, a deep channel will be formed near

the dashed I ine. Sedimentation will occur on the other side.

the only point which causes problems is the entrance, near the Zambezi. This point has to be dredged. It is to be expected that here

also in future sedimentation will occur. It is not possible to prevent this sedimentation and it is therefore advisable to concentrate

the sedimentation in a sand trap.

7.5.

The Iboka Canal

Highly urgent is an improvement of the overgrown section at the end of the Iboka Canal. Because no weedcutter is available at this momeni

it is recommended to remove the weed in the dry season (for example with scythes or sickles). Also a few shoals in this section have to be removed. In the lake bet\AJeen the Iboka Canal and the Little River the situation can possibly be improved by bandalling.

In the Iboka Canal itself the road-crossing causes some problems. Simply dredging this point is not possible without the

42.

construction of a (simple) bridge or ferry. At some other points the bottom and banks consist of sand. Because of waves the sand flows

into the canal, and causes shallow spots. This can be improved by means of a clay protection of the banks.

The shoals in the Lealui-Lake and the Sekeli-Lake should be removed regularly. This will cause not many problems because these

shoals wi 11 always occur at the same place.

The Rural Council short-cut should be deepened out with a ,dredge. Because the bottom consists of clay, hardly any naturally scouring wi 11 occur.

In the Iboka Canal the Hollandsche IJssel. dredge should be used, because of the narr6w canals and the fact that the improvements are made for small boats and not for the ba~ges.

7.6 . . The lower-section of the Luanginga

As already stated in chapter 4.6.1. hardly any problems occur in this section.

Only an improvement of the Nasilele Canal may be considered, but this improvement is of no great urgency.

77. The Luanginga near Mapungo School

In front of the Mapungo school and Hart's store the river is too wide and too shallow. The initial dredging of a channel and improvement bu banda11 1n9 may solve the problem partly. Regular maintenance can probably not be avoided.

The maintenance can be concentrated at a few spots by dredging sand traps just downstreams of feeding area's. A possible location of these traps is indicated on the map added to this report.

-43.

Furthermore it should be tried to prevent erosion of the escarpment. This can be done,in addition to a cla~ protection. by allowing the ~rowth of vegetation on the bank. Some types of grasses and bushes have to be selected for this purpose.

7.8. The Nasi lala Canals

The problems in the Nasilala Canals are more or less identical with the problems near Mapungo school, and therefore in general the same solutions may be proposed. An additional problem, however, is the loss of water

through the eastern bank. This problem can be solved by closing the gaps by means of a sand dam east of the Canal. This dam can be made from the sand-dump of the dredge. But here too the siltation problem cannot entir~ly be solved. and regular maintenance will be necessary.

7.9.

The Luanginga near Mwanga

Here only regular maintenance is recommended, in combination with sand traps, as indicated on the map.

7.10. The Namakuyu-c~nals and the junction near Malasha Store

The old Namakuyu canal causes no problems.

The new Namakuyu canal is superfluous therefore impr6vements

are not recommended, especially with regard to the financial situation. Whether a closing of the Luanginga-Luambimba connection shoutd be

considered cannot be said at this moment, because not enough is known about the currents in this connection.

7.11. The Luanginga north of Malasha Store

Because the Luanginga from Malasha Store up to Kalabo is sufficiently deep no dred9in~ is necessary.

The shal low short-cut north of Nalisheko should be abandoned.

The problems near Water-Affairs boat-landing can only be solved with very expensive; solutions; viz: a long short,...cut and a closing of the existing river, or by the construction of cribs in the river-.behd. A clay-protection is not expected to be sufficient here.

But with regard. to the costs, neither of these solutions can be recommended.

The Boma Canal has partly si lted up; and is overgrown with weeds and bushes. Rehabil itation of this canal will be expensive, and is not advisable, because the river, east of the canal is very well navigable. Therefore this canal should be abandoned.

figure 23

Improving the Kalabo-boat-landing can be effected by constructing a floating pontoon with a connection-bridge to the bank. The pontoon will follow the water level and

in this way a good berthiriq facility is created. But because the nowadays situation is causing no great problems, the

construc-tion of this pontoon is not urgent and can be postponed unti I a

later date. For the near future the maintenance of a gentle slope as boat-landing will be anaccep-table solution.

9.

FURTHER INVESTIGATIONS

9.1. Information still needed

Because this survey was carried out during high water, it was not possible to locate the navigation channels in the relative wide rivers; viz: the Little River, the lower section of the lower Luanginga and the Luanginga between Nal isheko and Kalabo. These sections should be surveyed during low water.This additional survey can be done in a period of approximately two weeks, because detailed maps are now <lvailable. The best period for this survey is the end of September or early October.

9.2. Continuous measurements

In general more depth-soundings and cross-sections have to be made to determine the shallow spots exactly. Besides these measurements the current-system has to be measured in order to give a good description of the morphology of the area.

Investigations to be carried out E'lt a later stage are exact

level ings of various points in the plain, and discharge measurements in various cross-sections in several channels and canals.

It should ·be tried to measu·re the sand-transport (bottom-transport) in the channels.

On the 1:20.000 maps more details should be'indicated, like the position of trees, the availabil ity of clay, and the various types of soils to be dredged.

This work should by done by a·Zambian surveyor. For this job. an assistant is required, with a reasonable education (one or two years secondary school) and m~ch interest in the area and in water works. It is possible to give a basic training for this man during a period of about two weeks. The rest of his training can be given by means of a correspondence course.

8.1. SUMMARY OF THE PROPOSED IMPROVEMENTS

Work to be carried out

Nebubela Canal

1. Dredging first section 2. Dredging middle section

3.

Dredging last section

4.

Maintenance shoal at junction

5.

Sand-dam south of canal L i tt 1 e Rive r 6. Short-cut· I 7. Short-cut II 8. Short-cut II I 9. Banda 11 s

New Sikolongo Canal

10. Dredging junction 11. Improvement junction Sikolongo Canal 12. Maintenance 13. Sand trap Iboka Canal 14. Weedcutting

15. I[)lproving this area 16. Iboka Canal (+ bridge) 17. Removing shoals

Lealui-Lake & Sekeli

Lake

18. Improving Rural Counci I Short-Cut ~ency 1 2 1 2 5 5 4 3 3

*

₃ 1 2 3 3 Time 3 months 2 months 2 months week ? month month month month 1 week· Means D.O. D.O. D.O. E/HIJ ·Dragline D.O. D. D. D.O. various 2 months DD/dragl. 2 weeks 2 weeks 2. months 2 months 1 month 2 weeks month various D. D., by hand E/HIJ HIJ HIJ HIJ

46.

Remarks

Exact location has to be determined during low water

Maintenance only necessary until work

II is finished

Bridge not included

<

47.

Work to be carried out Urgency Time Means Remarks

Nasilele Canal

19. Dredging &

river-closing 4 2 weeks D.D.

Mapungo School & HartIs

Store

20. Dredging 3 months DO/other time estimated for

D.O.

21. Bandalls 2 month

22. Closing rive rs near

HartIs Store 2 2 weeks DD/other

, ,

23. Erosion protection 3 2 months Dragl ine

24. Sand traps 3 1 week D.D.

25.

Maintenance

_'*

2 months E/HIJ

Nasilala Canal

26. Dredging & Mak i ng

sanddam 1 6 months DD/other

,

,

27. Bandalls 2 2 months

28. Sand traps 3 1 week D.D.

29. Maintenance

'*

2 months E/HIJ

Luanginga near Mwanga

30. Sand traps 2 1 week D.D.

31. Maintenance

_'*

2 mon'ths E/HIJ

D.O. Demas Dredge E

=

El icott Dredge

HIJ Hollandse IJssel Dredge

--~----~-~~~ ---~---~ ,L.::..., ~L----; ~ ~ , - - 4 \ " '\ , -~ , \

-, L _, \ j j I I

-

-I /5 , ) \ ' -\ , I " \ I --

~

-~AN\1<E \...AK.O ~S£'I<.E.\.\

I

CANAL/ I

~UI

"'PO\ll.lE.R -~- LINE -( -~ c ,--{ , , L',. >---' >----'\ ;--i "----i /--I '~

-

. / - --/ \ --7 ~ ,

-\ , '- "-/" , V

--o 5 10 1-5 '20 25 ktn. ~I~~~~I~---~I~~~~~'---~I~~~~I SCALE 1', '2S~ aCo

LUAN\KA- WA1ERwAY GENE~L su1<,VEY

~

..