Hazard Mapping Update

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					Hazard Mapping Update

New procedures are proposed to improve hazard mapping, where an accurate reflection of

hazard dynamics including sources of uncertainty is required in order to provide optimal

control measures and interventions for regional planning.

AdaptAlp Project Partner WBV (Abteilung Wasserschutzbauten der Autonomen Provinz

Bozen) proposed, within Work Package 5 “Hazard Mapping”, the use of scenarios to assess

flood hazards. As has been demonstrated in the article “Flood hazard assessment through

scenario analysis” (in press), this approach brings great benefits. There are two levels of

scenario: Loading System (LS) and Response System (RS). However, both should be used in

conjunction with one another. LS scenarios address the entire channel network, consisting

of confined, semi-confined and unconfined sections, whereas RS scenarios deal with areas

of potential substantial inundation (semi-confined to unconfined sections) and where

vulnerable buildings are already in situ or are planned.

LS scenarios are used to determine, for any given cross-section along the channel network

and within a given return period RI (e.g. 30, 100, 200 or 300 years) the anticipated type of

flow (e.g. debris flow, debris flood or bedload-water flows), the water discharge Qw, the

sediment rate Qs, and the driftwood rate Qlw. The resulting values provide the upstream

parameters for use in RS scenarios. In addition, LS scenarios locate sediment and wood

sources and identify sites within each section where channel changes are most likely (e.g.

bank erosion, bed incision) which will, in turn, assist in the design of correct control

RS scenarios are intended for the production of reliable hazard maps, drawing on the LS

scenario input on floodplains and alluvial and debris deposits. It is important for LS data to

be analysed extensively before carrying out a regional analysis of inundation patterns. The

number and extent of RS scenarios used to assess a catchment area depends on its size.

There can be two main types of regional domain in any RS scenario, depending on the

predictability of their dynamics, namely the stochastic and the quasi-deterministic

domain. The former represents the critical configurations whose dynamic evolution (e.g.

clogging by driftwood, failure due to breaching) cannot be realistically specified by

deterministic models, whereas the latter refers to the part of the system where flood

propagation can be computed with sufficient precision by hydrodynamic models. The

integration of these two dynamics allows us to predict in a more realistic way the course

and magnitude of flood events in the inundated area.

For practitioners, we have provided a handy, user-friendly guide on how to apply LS and

RS scenario analysis in mountain catchment areas, illustrating through flow-charts the

various steps technicians should adopt. This deals with LS scenarios first, followed by RS


For further information please contact Bruno Mazzorana,

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