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Remote sensing for resources development and environmental management
Damen, M. C. J.

Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986
Land use along the Tana River, Kenya - A study with small format
aerial photography and microlight aircraft
R. Beck
DHV Consulting Engineers, Netherlands
S. W.Taiti
Land systems and land use Consultant, Kenya
Research Institute for Nature Management, Netherlands
The study executed in 1984 and 1985 for the Netherlands Ministry of Education and Science, had as one of its
objectives to monitor land use on the riverine lands along the Lower Tana River in Kenya. Monitoring was
undertaken with a microlight aircraft equipped with small format cameras. A variety of land utilization types
was identified and located for the different parts of the floodplains and surrounding lands. These land
utilizations types are based on the association of land use practices, ethnic identities, ecological entities,
etc. wich coincide at locations with certain environmental conditions, of which the flooding regime of the
Tana River is a dominant factor.
The use of the microlight aircraft proved to be of great value during the surveys. Its use contributed greatly
to the completeness of the study in the very inaccessible area.
The photographs were flown over preselected areas, or randomly distributed areas met during the photoflights.
The photograps were produced in runs with forward and sideward overlap, enabling rotonly stereoscopic analysis,
but even their use in photoblocks.
L'étude exécutée de 1984 à 1985 par le compte du ministère neérlandais del'Education et des a Sciences avait
comme un des objectifs le monitoring de l'utilisation des francbords du fleuve Tana. Kenya.
Le monitoring est exécuté avec l'aide d'un avion u.l.m. équipé aves des caméras à petit format.
Un nombre de spectres d'utilisation des terres étaient identifiés et localisés pour les différentes sections
des francbords du fleuve et ses environs. Ces spectres d'utilisation des terres sont basés sur les techniques
et cultures de l'agronomie, l'élevage, les identités éthniques et les entités écologiques. Les spectres
coïncident sur des locations avec des conditions physiques spécifiques, dans lesquelles le régime d'inondation
du fleuve Tana est un facteur dominant.
L'utilisation de l'avion u.l.m. a rendu beaucoup de résultats pour l'étude sur un terrain inaccessible.
La photographie aérienne est réalisée pour des terrains sélectionnés avant ou pendant les vols. Les photos
sont produites en photoruns avec un recouvrement partiel, permettant l'analyse stéréroscopique, ou même en
1. Introduction
1.1 The Tana River Remote Sensing Study
The Tana River Remote Sensing Study (TRRSS) was exe
cuted in 1984 and 1985 by DHV Consulting Engineers in
cooperation with the Delft Hydraulics Laboratory, the
Institute for Nature Management all from the Nether
lands together with Landevco from Kenya.
The study, financed by the Dutch Ministry of Educa
tion and Science, was carried out in conjunction with
the Tana River Morphology Study (TRMS) in which the
same organizations participate and which is carried
out for the Tana and Athi River Development
Authority.This TRMS is carried out with the objective
to analyze the effect of current and future interven
tions, such as reservoirs for power generation, irri
gation schemes and bridges on the morphology of the
river and the riverine lands.
The TRRSS had the objective to test innovative remote
sensing methods on certain specific research areas in
the context of an operational project, the TRMS.
Apart from this methodological objective, the results
of the TRRSS are of course of great interest to the
TRMS. Data collection with respect to the selected
research areas would involve huge means in terms of
logistics and manpower when no use would be made of
remote sensing techniques.
1.2 Environmental setting
The Tana River is the largest perennial river in
Kenya and its most important surface water resource.
It rises from both Mount Kenya and the Nyandarua
ranges in Central Kenya and enters the indian Ocean
between the towns of Lamu and Malindi.The catchment
area of over 100,000 km2 covers approx. 20% of the
Kenyan territory. The lower Tana River, the subject
of the present studies covers the alluvial downstream
half of the river course (625 km.), as well as the
riverine lands along the river. These riverine lands
are in fact floodplains, which start at the beginning
of the study area and reach to the sea, where the
Tana Delta covers an area of some 3000 km2. In Figure
1 the upper part of the study area is presented as
viewed by Landsat .
These floodplains consist physiographically of two
units, the levees and the river basin lands. However,
the climate and hydrological characteristics as flow
velocity and frequency and duration of inundations
result in a totally different landscapes, natural
vegetation and land use in different parts of the
The mean annual rainfall in Tana Delta exceeds 900
mm, the northern parts of the study area have a semi-
arid climate with less than 300 mm/year of rainfall
spread over two rainy seasons.
Largely under direction of the Tana and Athi Rivers
Development Authority, the national policy concerning
the Lower Tana River has changed abruptly in recent
years, the main reason being concern for Kenya's
energy and food supply and the realization of the
irrigation potential of the Lower Tana River where
200,000 ha of land are regarded as potentially suita-