Environmental Engineering Reference
In-Depth Information
Table 5.1. Home industries growth rate in
Kuwadzana.
Year
Number of home industries
Before 1980
0
1981-1985
9
1986-1989
11
1990-1993
25
1994-1997
48
1998-2001
82
leather craft. In addition, street vending and small-scale urban informal agricultural
activities are a widely spread practice.
The study area forms part of the Marimba River catchment, which has a total of 189
km
2
and is a sub catchment of the Manyame River, as presented in Chapter 3. The
geological formation of the study area mainly comprises four major rock formations. The
eastern part of the area comprises course to medium grained, quartz-rich clastics with
preserved or remnant sedimentary textures. The western part that contains the home
industry comprises Mashonaland dolerite. The northern part consists of Metadacite of
Passfor formations (Baldock et al. 1994). Based on the classification system proposed by
Nyamapfene (1991), the major soil types in Harare are kaolinitic. They are moderately to
strongly leached soils. Clay fractions are mainly inert, together with appreciable amounts
of free sesquioxides of iron and aluminium. The soils are either classified as fersiallitic
(mixed clay) or paraferrallitic (inert clay) or orthoferrallitic (very inert clay) soils. The
important consideration is that all these formations are rich in ferro-magnesium minerals
and this results in clayey soils that are red, reddish brown to yellowish red in the drained
areas.
In order to obtain information regarding the specific patterns of land use practice, the
storm water drainage system and the general condition of the infrastructure, two
reconnaissance visits to this specific area and other possible alternative options were
done. It was found that most of the high-density suburbs have similar physical set up with
the location of the home industries along the streams nearby. The types of the informal
sector activities were very much alike in the different suburbs visited and correspond to
the description made above. During the second visit, the natural drainage pattern was
identified by the use of topographic series maps of Harare TR8027 and TR8025. The
major drainage channels from different land uses such as residential only, residential and
part of home industries, residential and runoff from informal agriculture were identified,
with corresponding drainage areas. Also, it was observed that the adjacent stream to
Kuwadzana 1 home industry area was flowing during typical dry season conditions (after
6 months of a dry spell), indicating the presence of perennial flow. This suggests that the
presence of base flow is due to groundwater recharge. An approximate estimation of the
base flow rate was done by the application of the velocity-area method (Mays 2001).
Physical investigation and the geology of the area confirmed the perennial nature of the
