| dc.creator |
Nyandwi, Ntahondi |
|
| dc.date |
2016-07-21T14:13:23Z |
|
| dc.date |
2016-07-21T14:13:23Z |
|
| dc.date |
2001 |
|
| dc.date.accessioned |
2018-04-18T11:12:31Z |
|
| dc.date.available |
2018-04-18T11:12:31Z |
|
| dc.identifier |
Nyandwi, N., 2001, June. Reassessment of the nature of beach erosion north of Dar es Salaam, Tanzania. In Marine Science Development in Tanzania and Eastern Africa. Proceedings of the 20th Anniversary Conference on Advances in Marine Science in Tanzania (Vol. 28, pp. 107-120). |
|
| dc.identifier |
http://hdl.handle.net/20.500.11810/3358 |
|
| dc.identifier.uri |
http://hdl.handle.net/20.500.11810/3358 |
|
| dc.description |
An assessment of the status of coastal erosion along the coastline of Tanzania,
including the Zanzibar islands, through field surveys, revealed that the problem
is widespread but more serious along the Kunduchi beach, to the north of
Dar es Salaam city. Analysis of wave climate data, drogue tracking, current
measurements and beach profiles obtained during both the NE-monsoon
and SE-monsoon periods shows that the prevailing erosion is mainly a result
of combined effects of high tidal levels and strong waves. Wave heights at
Kunduchi beach are about 0.5m during the NE-monsoon period and increase
to about 0.9m during the SE-monsoon. Such wave climate in combination
with high tidal range of up to 4m results in increased wave erosion during
high spring tides. Beach profiles made during selected periods indicate that
erosion is generally more severe during the SE-monsoon period, especially
during July/August/September. It was also found that erosion intensity
depends on both shoreline geology and nearshore bathymetry. Owing to the
nature of the bathymetry, waves are focused selectively at some sections of
the shoreline while the rock type of each section determines the ease with
which it erodes.
Tidal circulation in the area appears, as a rule, to flood from the north
and ebb in the reverse direction. Analysis of the various drogue tracks cast
seaward of the breaker zone during both the NE and SE monsoon periods
shows a net southward transport which is confirmed by current
measurements. Grain size data and sedimentary structures from the beach
and within the breaker zone on the other hand point to a net northward
transport. The contrast shows that whereas the beach and breaker zone
sediment dynamics is largely driven by the action of breaking waves which
are stronger during the SE monsoon, the dynamics outside the breaker
zone is driven mainly by tidal circulation. The supply of sand from rivers
and creeks draining into the area contributes the bulk of the sand that is
being moved along the beach. The growth of large spits across creek
mouths are attributable to the alongshore deflection of the ebb jets out of
the creeks. |
|
| dc.language |
en |
|
| dc.title |
Reassessment of the Nature of Beach Erosion North of Dar Es Salaam, Tanzania |
|
| dc.type |
Conference Paper |
|