In a recent article by Hepworth, R, entitled 'A Direct Approach to Storm Sewer Design' (New Civil Engineer, 14th Nov. 1974, IRRD abstract no. 212672) the TRRL hydrograph method is challenged on the following three main points:- (a) The method makes illogical and visibly unreal assumptions about the behaviour of storm water. (b) The correlation procedure used to 'fit' calculated flows to measured flows in technical paper No. 55 is unworkable in a design method and attempts can lead to gross errors. (c) The 'Direct Method' is simpler to understand, simpler to use, and gives a closer fit with recorded flows. In this letter the authors defend the TRRL method, and deal with the three points in turn. In particular it is pointed out that Hepworth ascribes to the TRRL method assumptions that are not really made. Results are also presented of 30 out of 286 events on 4 out of 12 catchments, which are quoted by Hepworth and which also appear in t.p. 55. It is suggested that a comparison of these figures does not support the conclusion made in (c) above, that the 'Direct Method' gives a closer fit with recorded flows. (Subsequent correspondence from Hepworth follows this letter). /TRRL/

Media Info

  • Features: Tables;
  • Pagination: p. 16-7
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00125077
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Files: ITRD, TRIS
  • Created Date: Oct 18 1975 12:00AM