botswana/namibia - Cour international de Justice

303. The Namibian Memorial exhibits confusion and misunderstanding relating to the erosion
processes of rivers. It states:-
"The sandy material making up the banks of the northern channel is readily erodable. Yet the
close up ground photographs of these banks show no sign of appreciable bank erosion,
sediment deposition, or reed growth normally associated with actively flowing river channels
in general." (Namibian Memorial, p.55, para.152).
304. This presents a wholly misleading account of the sedimentation process in a mature
river. The Sedimentological Report provides the history of the pattern of sedimentation on the
Island. From this it is apparent that the top layer of 1.5 metres in depth constitutes, and has
done for thousands of years, material for stable non-erodible banks. These are plainly visible
and indicate the stability and maturity of the Chobe system in the vicinity of the Island. The
presence of trees on the right hand (island) bank of the northern channel also indicates an
established stable channel. There are no erosion scars or slump cracks on the edge of the
island that can be attributed to water action. Dating techniques applied in the course of the
Sedimentological Study of the Island show that material along the island bank of the northern
channel is more recent than the deposits in the southern channel: see Chapter 6, paras. 368-71.
305. Stable and non-erodible banks are a characteristic of perennial, not ephemeral rivers. To
determine, as does Professor Alexander, a main channel by the absence of erosive features
along its banks, suggests a poor understanding of river processes and the impact of climate on
geomorphic processes.
(viii) The misrepresentation that the sand bars in the Chobe River indicate flow
306. The Namibian Memorial advances the following theory on sand bars:-
"The existence of these sandbars and the changes in their position over the years, as illustrated
by the successive photographs, indicate active river flow. The location of the bars,
immediately adjacent to the foot of the Chobe Ridge shows that this is the zone of maximum
velocity along which the water and sediment are being transported through the floodplain
towards the exit at Mambova Rapids". (Namibian Memorial, p.56, para.155).
307. This is not correct. Sediment bars located at the bifurcation point of the northern and
southern channel and on the right of the southern channel in the big meander loop are
permanent features of a low energy river. They are relict bars of earlier downstream flowing
channels, not active zones of sedimentation. Absence of any such bars in the northern channel
indicates strength of flow.
308. The Spur channel immediately south of Kabuta serves as a flood relieving channel for
the northern channel. It is indeed a relict channel and its greater depth is explained in terms of
palaeo-hydrological conditions. The northern channel actually joins the original channel of
which the Spur channel was part. It may be noted that at cross-section 5 of the 1985 Joint
Survey Report the depth is at 9.2 metres.
309. Vegetation along the banks of rivers may indicate flow or lack of flow but care in
identifying species is required. There is an association of placidity of water and weed growth
and proliferation of weed growth within a given decade may indicate sluggishness of flow.
Hence the paler area plainly visible in the western section and the 'lagoon' sector of the