Robson, A.J., Reed, D.W. 1999. Statistical procedures for flood frequency estimation. Vol. 3 of Flood Estimation Handbook, Institute of Hydrology, 338 pp. [Sole author of 4 chapters; joint author of 8 chapters.]
This volume presents statistical procedures for flood estimation. Much of the content is concerned with estimating a flood peak of given rarity: the so-called T-year flood, where T expresses the event rarity as a return period in years. Concepts and terminology are introduced and explained throughout the volume. The introductory chapter provides a brief overview of what is to follow. In addition, it offers a road-map (Figure 1.1) to the statistical procedures for flood frequency estimation and their arrangement in Volume 3.
Volume 3 is divided into two main parts. Part A (Chapters 2 to 9) provides a 'slim guide' to the statistical procedures for flood estimation. Part B (Chapters 11 to 21) presents the supporting theory and results. This arrangement is designed to support effective use of the statistical procedures, while at the same time encouraging users to understand and explore the methods. These twin targets are addressed by an algorithmic Part A and an expository Part B. Inevitably there is some duplication and restatement. Cross-references are given in chapter headings, to highlight the complementary roles of Parts A and B. Those interested principally in the basis of the methods may wish to refer directly to Part B.
A final part to the volume (Part C, comprising Chapters 22 and 23) introduces the FEH flood peak datasets and gives broad guidance on the acquisition of flood peak data. Chapter 6 of Volume 1 provides additional advice on finding data.
Do people apply complicated methods before digesting the basic principles? The answer is an unequivocal "Yes". So the important chapter entitled "Introducing the flood frequency methodology" has been placed at the beginning of Part B rather than Part A, in the hope that what has not been force-fed will be the more appreciated. It is essential reading to those unfamiliar with statistical frequency analysis, and to all but the most experienced and instinctive user of the WINFAP-FEH software.
It is anticipated that relevant software will evolve during the lifetime of the Handbook. For this and other reasons, Volume 3 presents and illustrates the statistical procedures with relatively little reference to particular software packages.
Because some of the flood estimation procedures are intricate, and much of the guidance in their use is open-ended, many users will inevitably find the FEH difficult to use. But flood frequency estimation is an intrinsically difficult and uncertain task: the user who expects to find it easy is probably not looking deeply enough.
The best flood estimates will combine the effective use of flood data and software with a strong dose of hydrological and statistical judgement, reinforced by detailed understanding of the study objective and the subject catchment – quite a challenge!