BASANIA HEP_PFR - Ministry of Power

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Preliminary Feasibility Report
Basania HE Project 3 X 30 MW
reservoir elevation-area-capacity curve at Basania H.E. project site adopted for
the present study is given in Figure 5.1.
5.5 DESIGN FLOOD
A concrete dam is proposed to be constructed at proposed site Basania on
Narmada River with gross storage capacity of 1848.94 Mcum. The gross storage
capacity is more than 60 Mcum and the height of the dam is more than 30m.
Therefore, As per Central Water Commission criteria and IS-11223-1985, the
spillway of the proposed Basania dam has to be designed to negotiate probable
maximum flood.
5.5.1 PREVIOUS STUDY (MPEB-1974)
Estimation of design flood discharge for the design of spillway, two methods
namely Snyder synthetic unit hydrograph and empirical formulae had been used.
Design storm on 19 to 20 September 1926 having Bichhia as center had been
chosen from isohyetal maps of important storm in Narmada basin and used after
increasing it by 20%. The result obtained from Snyder synthetic unit hydrograph
using above design storm was higher as compared with other method. Thus, the
design flood discharge 39,368 cumec by Snyder synthetic unit hydrograph was
adopted.
5.5.2 PRESENT STUDY (NHPC)
Design flood estimation may be done by following approaches:
• Deterministic approach
• Probabilistic approach
• Empirical formulae
Deterministic approach
Due to non-availability of observed flood hydrograph, rating curve and other
relevant data, computation of design flood using deterministic approach has not
been done at this stage.
NH/CON/229 27 01/2004