Site Selection, Survey and Treatment Plan - Afforestation, Reforestation and Forest Restoration in Arid and Semi-arid Tropics - page 57

skilled labour, and yields high productivity of labour (a team of four persons working
an 8-h day can mark 1000 m of line per day).

3.7 Setting Out Engineering Structures with HSL

Structures like earthen embankments and weirs can be conveniently and accurately
located and set out using a theodolite or a dumpy level. However, use of these
equipment requires trained persons often not available in afforestation programmes.
To get around this limitation, the following paragraphs briefly explain how the HSL
can be used to align, design, and set out such structures.
In order to design an earthen embankment or a weir, it is only necessary to obtain
the cross section of the stream at the desired location. For this, the HSL is positioned
at one bank of the stream at the highest point to be included in the cross section.
The two staffs will read equal. Now the forestaff is placed a fixed distance across
the stream bed (say 1.5 m each time), such distance being measured horizontally in
case of a steep bank and along the ground if the slope is not too steep. The difference
between the two staff readings is noted in the relevant column of a table (Fig. 3.4 ).
When water in the lower staff reaches maximum reading (begins to spill) the rearstaff
is shifted ahead and the process continues until one reaches the highest point on the
opposite bank. Each of the staff stations is marked with letter a , b , c or 1, 2, 3 etc.
Stone boulders may be marked with paint and placed at these points. The table is then
computed for the levels of the points and the cross section is plotted on a graph sheet,
usually the vertical scale being exaggerated by a ratio of two or three compared to the
horizontal scale. The cross section so obtained allows one to choose an appropriate
height and width of the structure to be designed. The same points marked on ground
will be useful while setting out the structure.
The longitudinal section of a stream (the L-section) can be obtained similarly.
The ground slope along the stream is likely to be much less compared to the slope
of ground in its cross section. Therefore, it will suffice to record ground distance
as the horizontal distance. The horizontal interval between staff points can be much
larger (10 m or more) and the process can be repeated by alternately exchanging the
forestaff and the rearstaff. It is possible for a team of four persons to draw about 1 km
of L-section in a day.

3.8 Site Treatment Plan

Treatment plan is the blueprint of the work that must be carried out in order to
successfully afforest an area. The aims and objectives of the programme and the
technical considerations—based on factors such as terrain relief, soils, and climate—
determine the ingredients of a treatment plan. Survey work done earlier helps in
estimating the quantities of each type of work. Having determined all the work items