BOX 2

IJPP ­ Italian Journal of Planning Practice 42Vol. III, issue 1 ­ 2013

Piera Pellegrino

ISSN: 2239­267X

Architect, PhD in Town and Regional Planning
Dipartimento di Pianificazione, Design, Tecnologia dell'Architettura ­ Sapienza Università di Roma

The Strategic Urban Structure (SUM) has been introduced within the Law of
Umbria Region 11/05 (Art. 3) as a fundamental tool to reduce urban seismic
risk through planning. Its definition is provided by the Guidelines with the
same title (SUM)1, addressed to technicians working within Public
Administrations at the local level, as well as to planners and urban designers.
The SUM refers to the basic system of streets, open spaces, strategic functions
and buildings whose contribution is fundamental for responding to the
earthquake in the emergency phase and for the re­start of socio­economic and
urban activities after a seismic event. The SUM includes the basic
components, none of which can be subtracted without compromising the
functioning of the settlement.
The SUM can be considered as analytical and also as a planning tool. In fact,
aiming at improving the “urban response” to the earthquake, it is grounded on
the present condition of places, but it considers also planning forecasts,

STRATEGIC URBAN STRUCTURE (SUM)
Concept, components, phases and references

See references.1



IJPP ­ Italian Journal of Planning Practice 43Vol. III, issue 1 ­ 2013

Pellegrino ­ Box 2: Strategic Urban Structure (SUM)

defining what is needed in terms of spaces and places, functions and routes, in
order to increase its efficiency. From a planning point of view, the re­start of
the city after a seismic event is as important as the ability to resist the
earthquake in the emergency phase: for this reason, the SUM is composed of
strategic elements that can fulfil both purposes. It also highlights the
criticalities that must be solved to ensure a better functioning of a town in
case of a seismic event and therefore it is useful for defining public actions,
and priority actions. It is important to clarify that the SUM does not only
include the contents of a Civil Protection Plan, but it contains all the elements
that are necessary for the functioning of the city both in the emergency and
post­emergency phases.

Defining the SUM
The definition of the SUM is addressed to the reduction of seismic risk and
consists of three steps that correspond to three basic planning stages:

1.

mobility and accessibility (the main transport and
communications network, the main connections between
strategic functions, etc.);

Identifying urban structure through analysis of the urban functioning
and identification of its strategic components for the response to an
earthquake. This includes both the present elements and those
foreseen by planning tools. The main systemic components of the
urban structure are:

The SUM also includes buildings and places that contribute to the
representation of economic, social and identity values. Their loss
may affect the functioning of the city, and particularly the post­
seismic restart.

2. Assessing criticalities through the identification and evaluation of
potential problems and weaknesses of strategic components of the
SUM. The evaluation consists, first of all, in a qualitative

•

•
•
•

safe open spaces;

main technological networks.

strategic buildings (administrative institutions, health facilities,
police, fire department, etc);



IJPP ­ Italian Journal of Planning Practice 44Vol. III, issue 1 ­ 2013

assessment. Further in­depth assessments can be conducted
according to different levels of detail which are needed, and
according to the knowledge and resources available. The evaluation
regards the main following critical issues:

3. Definition of the actions needed to reduce criticalities and to increase
the functionality of the SUM. These actions should be consistent with
planning needs, and also consistent and integrated with the operational
needs of civil protection. Specifically interventions concern:

Improving the functionality of the SUM could mean providing the
redundancy of some of its elements. There are two main reasons why
the SUM must be characterized by redundancy, both related to forms
of uncertainty. The first is uncertainty about possible concatenations
or side­effects provoked by the seismic event, and to the multiple
situations which could occur; the second is uncertainty about the
behaviour of the urban settlement (which is also related to human
behaviour).

Pellegrino ­ Box 2: Strategic Urban Structure (SUM)

structural damage;•
•
•
•

absence or lack of safe spaces;

local seismic hazard conditions;

absence or lack of safe routes, considering in particular
situations of overcrowding;

•

•
•

amplification of the seismic effects, in particular when the
damage of a single element leads to a systemic loss of
functionality;
general systemic weakness.
potential problems with communications;

reduction of the weaknesses of the systems;•
•
•

improvement of the urban structure with the definition of
alternatives, or with the creation of elements of redundancy;
definition of new planning goals more consistent with
environmental risk reduction imperatives.



IJPP ­ Italian Journal of Planning Practice 45Vol. III, issue 1 ­ 2013

REFERENCES
Regione Umbria – DPTU, Dipartimento di Pianificazione Territoriale e

Urbanistica, Sapienza Università di Roma: F. Fazzio, M. Olivieri, R.
Parotto, B. Pizzo (2009), Linee guida per la definizione della Struttura
urbana minima all’interno del Prg – parte strutturale. Law 11/05 (Art.
3) of Umbria Region Rules of local government: municipal planning.

Table 1 ­ The phases and related products for the definition of the SUM

Pellegrino ­ Box 2: Strategic Urban Structure (SUM)