regional flood frequency analysis using dimensionless index flood method

regional flood frequency analysis using dimensionless index flood method

hydrologic designs require accurate estimation of quartiles of extreme floods. but in many developing regions, records of flood data are seldom available. a model framework using the dimensionless index flood for the transfer of flood frequency curve (ffc) among stream gauging sites in a hydrologically homogeneous region is proposed.

key elements of the model framework include: (1) confirmation of the homogeneity of the region; (2) estimation of index flood-basin area relation; (3) derivation of the regional flood frequency curve (rffc) and deduction of ffc of an ungauged catchment as a product of index flood and dimensionless rffc. as an application, 1983 to 2004 annual extreme flood from six selected gauging sites located in anambra-imo river basin of southeast nigeria, were used to demonstrate that the developed index flood model: 𝑄𝑚=0.495𝐴0.6676, overestimated flood quartiles in an ungauged site of the basin. it is recommended that, for wider application, the model results can be improved by the availability and use of over 100 years length of flood data spatially distributed at critical locations of the watershed.