Geology Reference
In-Depth Information
N
Land use
Cropland
Orchard/cash
Wood/shrub
Wasteland
Vegetables
Fallow
Fig. 12.3 Scenario land-use
(15° cropland limit) for the
Danangou catchment.
250
0
250
500
750 Meters
cannot be implemented directly in LISEM (e.g. by
changing the DEM). Instead, such measures were
incorporated by changing other parameters that
are influenced by them. For example, it can be
expected that the use of contour ridges will
increase infiltration because water storage on the
slope is increased. One can then increase, for
example, saturated conductivity to produce such
an increase in infiltration. In this way all the pro-
posed measures were translated into changes of
input parameters for the LISEM model (Table 12.2).
Table 12.2 gives assumed multiplication factors
for the original LISEM input dataset: for example,
a value of 1.25 for 'fallow biological' plant cover
means that the data that apply to the 1 August
storm event were multiplied by 1.25.
Table 12.1 Areas (%) occupied by the different land
uses for the different land-use maps. Catchment area
is 3.52 km 2 .
Land use
Present
25°
20°
15°
Cropland
35.4
21.0
13.0
6.7
Orchard/cash tree
2.4
0.0
9.5
17.8
Wood/shrubland
13.4
38.2
38.4
38.3
Wasteland
41.4
35.5
35.7
35.6
Vegetables
0.1
0.1
0.1
0.1
Fallow
7.3
5.2
3.2
1.6
so-called design storm would not allow calibration.
An event that occurred on 1 August 1998 was cho-
sen because it was large enough to cause erosion,
and because it produced rainfall over all the catch-
ment. The simulations were carried out with
LISEM LP.
The total catchment area of 3.5 km 2 made sim-
ulation with pixels smaller than 10 m impracti-
cal. Many soil conservation measures are much
smaller in scale than 10 × 10 m and therefore
12.6 Results
12.6.1 Data collection
The measured discharge events occurred on: 1
August 1998, 23 August 1998, 20 July 1999, 21
July 1999, 11 August 2000 and 29 August 2000.
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