Flood Estimation using the Revitalised Flood Hydrograph Method (ReFH)

Flooding and flood risk management is of major importance following high profile and devastating floods in recent years. This has increased the requirement for flood risk assessments and increased the scrutiny on those who manage and design bridges and culverts including local authority engineering departments. The Flood Estimation Handbook (FEH) methods provide the standard methodology for flood design but can be time consuming to implement without the associated software.

This 1 day course provides expert tuition in the Revitalised FEH Flood Hydrograph Method which replaces and offers significant improvements over the original FEH rainfall-runoff method. Delegates will implement the methods using ReFH software and derive a design flood hydrograph of a given rarity which can be routed through a reservoir or used as the input to further hydraulic modelling packages. With tuition from the lead researcher on the ReFH development team, delegates will gain a unique understanding of the key principles of the ReFH method and rainfall-runoff modelling generally and learn where it can be most suitably applied.

This course will enable delegates to:

• Choose between the different FEH methods for flood estimation
• Determine which FEH method is most appropriate in different situations
• Understand the different models within the Revitalised Flood Hydrograph method of flood estimation, the background science and reasons for its development
• Estimate model parameters from catchment descriptors and flood event data
• Transfer data from donor gauged catchments
• Use ReFH software to construct a design flood hydrograph
• Simulate runoff from an observed rainfall event and compare with the gauged hydrograph.
• Adjust the parameters of the ReFH model as necessary to improve fit with observed events
• Use ReFH to route the design hydrograph through a reservoir.
• Know when to apply the ReFH model
• Understand the limitations and strengths of the ReFH model and interpret results correctly

The course will enable delegates to produce a flood design hydrograph and if desired route this through a reservoir. Also they will be able to simulate the runoff from observed rainfall events and compare these to any gauged data. By understanding the science behind the software you will be able to use it more effectively and interpret the results more fully, appreciating the strengths and limitations of the chosen method. Delegates will also have a better understanding of situations when the ReFH method is most appropriate, or when other FEH methods may be more suitable.

Introduction

• Background
• Design flood estimation
• Choice of method
• FSR/FEH vs ReFH

The Revitalised Flood hydrograph (ReFH) Model

• Model structure
• Loss model
• Routing model
• Base-flow model

Model Parameter Estimation

• Introduction
• Estimation from observed events
• types of data
• base-flow
• model antecedent soil moisture
• optimisation
• Estimation from catchment descriptors
• Data transfer from donor sites
• Exercise 1 – Introduction to the ReFH modelling system

Design Flood Estimation

• The ReFH design method
• Design rainfall
• Depth
• Duration
• Seasonality
• ARF
• Rainfall profile
• Initial soil moisture Cini
• Initial base-flow BF 0o
• Alpha parameter
• Exercise 2 - Design flood estimation

When to use ReFH

• Environment Agency guidelines
• Urban catchments
• Permeable catchments
• Small catchments
• Reservoir safety
• Flood risk mapping
• Exercise 3 - Simulation of an observed event

This course uses an interactive combination of presentations, practical hands-on exercises and discussion.

It is presented in 4 sessions including 3 supervised practical exercises addressing key aspects of the course.

The presentations are supported by comprehensive course notes and worked examples to provide a valuable reference source.

With a maximum of 12 delegates per course we aim to make our training as informal as possible with plenty of time for questions and discussion.

Our trainer led the scientific development of the REFH model and authored FEH Supplementary Note no. 1. It has been commented that “he provided a good knowledge of ReFH and other FEH methods which was very useful”.

Others commented that “the course was very interesting and informative”; “the practical experience was good”; “good to make session informal with discussion opportunities”.

This course is particularly suitable for existing users of FEH methods who are new to the ReFH model or who want to consolidate existing knowledge and learn of the latest scientific advances. The course will be of particular interest to engineers and modellers from consultancies involved in flood risk management, highway and urban drainage designers and development control and consenting officers. As all the key principles of the method are covered, the course will also provide a valuable introduction for those new to event based rainfall-runoff modelling but who already have some knowledge of flood design concepts.

There are no pre-course requirements, although non specialists may find our Introduction to Hydrology course useful. This REFH course assumes a basic understanding of flood hydrology and the general concepts and terminology of flood design. Course notes will be provided on the day and no pre reading is required. The trainer is always happy to advise delegates who may have specific questions from working in this area.

Laptops will be required