Introduction

This section describes the methodology used in MAST.  The section assumes the reader has a good working knowledge of the probability of extreme events and some familiarity with joint probability methods as described in Hawkes (2005), FD2308 Use of joint probability methods in flood management: a guide to best practice.

A flow chart for the methodology is shown in Figure 1, and a typical application of the methodology is described as follows:

Stage 1 - Data collection

Collect existing flood information maps at national and possibly local scales.

Collect information on uncertainty and dependencies, if available.

Collect information on different scenarios (management options, data for future climates) if required.

Stage 2 - Use map combination approach to generate combined flood map

Use the software tool to generate an 'initial' combined map

Use tool outputs to assess locations where dependency may generate interactions, and decide whether these are in high consequence areas.

Use tool outputs to assess areas where uncertainty is high, and decide whether these are in high consequence areas

Stage 3 - Local modelling

Where necessary, use local models to map flood risk from combined sources and feed back into stage 2.

Where necessary, use local models to map risk more accurately in high consequence areas and feed back into stage 2.

The two components at the core of this methodology are:

Figure 1  - Flow chart for combined mapping of flooding from all sources