376
Figure 1. Study area as part of Eastern Kenya,
including Landsat mosaic of june '75, band 7.
ble for irrigation. The strategy of opening up and
incorporating the Lower Tana River area includes the
establishment of large scale irrigation schemes and
the utilization of Tana River water for the genera
tion of elecricity by the construction of reservoirs
in the middle reaches of the River. This policy
objective is being pursued vigorously.
In the development scenario outlined above the beha
viour of the flooded river in the floodplain is felt
as an outstanding constraint. It creates difficul
ties of accessibility, damages infrastructure and in
general impedes these development efforts.
A major problem for these development efforts of land
in the lower Tana River is the way in which the land
is held and used by the traditional communities
inhabiting the area, of which very little is known,
in official records. Small sedentary communities live
by growing rice and maize on basin lands and levees,
mainly relying on flood water which comes once or
twice a year. Practices related to agriculture
include cutting down and burning of forest, digging
of channels from the river to the shainbas, pumping of
water and excavation of canals for irrigation. In
the midst of the agricultural communities and around
them land is occupied by groups of pastoralists,
keeping cattle in combination with various other
animals such as sheep, goats, donkeys and camels.
The main pastoral groups are nomadic, migrating
between different parts of the floodplain or between
the riverine and outlying lands in different seasons
of the year.
1.3 Objectives of the described study
The land use in the study area is of a very complex
nature given the relationship between this land use
and a highly dynamic river and riverine environment.
The consequences of changes in land use, due to the
implementation of irrigation schemes or changes in
the hydraulic regime due to the construction of the
hydro-electric power dams are not all that easy to
analyse given the nature of the environment.
It is therefore important to carry out an inventory
of land utilization types (land utilization types),
with emphasis on the relation between the land utili
zation types and the hydraulic regime.
The TRMS study yields results on expected changes in
the morphology of the river. These results can be
combined with the results of the inventory and des
cription of the "hydro-environmental land utilization
types".
The objective of the study component on which this
article reports can be summarized as the testing of
low-cost remote sensing techniques in the inventory
of land utilization types in the remote and inacces
sible floodplains of the Tana River.
The use of low-cost remote sensing techniques was
required given the limited budget of the study. The
budget also did not allow a quantitative analysis
(with a satisfacory amount of data and field sam
ples), but this was not felt as a serious constraint
given the objective and the much more information
yielding inventory than imagined possible during the
start of the TRMS.
This article reports on the methodology using micro
light aircraft as a platform for vertical and oblique
aerial photography which was of great use in the
inventory, together with Landsat-imagery and existing
small-scale aerial photography. It also presents some
results of the inventory of land utilization types in
relation to the hydraulic regime of the river and of
course the physiography and climate of the riverine
lands.
2. Methodology
2.1 Land utilization types
It is assumed that traditional land use patterns bind
together the information concerning the climate, the
soil, the river and the history and the capacity of
the people to develop or improve their situation.
From this assumption and the high spatial variability
within the floodplains it follows that land utiliza
tion types can be described for many different cases.
However the limited study budget and the demonstra
tion character of the project did not allow a tho
rough inventory of all these land utilization types,
therefore a generalization was performed after the
collection of all study data. This generalisation
resulted in four broad land utilization types, with a
however consistent relation between land use and
hydraulics.
The description of these land utilization types is
based on data collected during different fieldwork
periods and the study of existing literature,
Landsat-imagery and existing aerial photographs. The
fieldwork consisted of three periods in which obser
vations were made during the different seasons, du
ring floods and during periods of drought. The tec
hniques for data collection in the project were the
use of interviews, descriptions of vegetation and
soils, and the use of a microlight aircraft as a
platform for vertical and oblique aerial photography
as well as visual reconnaissance.
2.2 Use of existing information, aerial photography
and satellite imagery
Literature of the study area exists albeit in
scattered and separate hoards. This information has
been reviewed prior to the collection of additional
data. The literature covers topics such as policy
and planning, physiography, human population and
settlements, climate, wildlife and ecology, soils,
land use , water utilization and productivity. Howe
ver, the data in the literature do not always provide
a consistent starting data base.
For instance do the population data of the national
census of 1979 not contain a breakdown for riverine
and nonriverine areas in the Tana River District,
neither do they contain the geographical distribution
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