Comprehensive Risk Assessment for Natural Hazards - Planat

Comprehensive risk assessment for natural hazards
Discharge:* Volume of water flowing through a river (or
channel) cross-section in unit time.
Elements at risk:** The population, buildings and civil engineering
works, economic activities, public services,
utilities and infrastructure, etc. exposed to hazard.
El Niño:*** An anomalous warming of ocean water off the
west coast of South America, usually accompanied by
heavy rainfall in the coastal region of Peru and Chile.
Envelope curve:* Smooth curve which represents the
boundary within which all or most of the known data
points are contained.
Flash flood:* Flood of short duration with a relatively high
peak discharge.
Flood:*(1) Rise, usually brief, in the water level in a stream
to a peak from which the water level recedes at
a slower rate.
(2) Relatively high flow as measured by stage height
or discharge.
(3) Rising tide.
Flood forecasting:* Estimation of stage, discharge, time of
occurrence and duration of a flood, especially of peak
discharge, at a specified point on a stream, resulting
from precipitation and/or snowmelt.
Flood plain:* Nearly level land along a stream flooded only
when the streamflow exceeds the water carrying capacity
of the channel.
Flood-protection structures: Levees, banks or other works
along a stream, designed to confine flow to a particular
channel or direct it along planned floodways; a floodcontrol
reservoir.
Flood routing:** Technique used to compute the movement
and change of shape of a flood wave moving through a
river reach or a reservoir.
Hazard:** A threatening event, or the probability of occurrence
of a potentially damaging phenomenon within a
given time period and area.
Hydrograph:* Graph showing the variation in time of some
hydrological data such as stage, discharge, velocity, sediment
load, etc. (hydrograph is mostly used for stage or
discharge).
Ice jam:* Accumulation of ice at a given location which, in a
river, restricts the flow of water.
Mean return interval:** See mean return period.
Mean return period:** The average time between occurrences
of a particular hazardous event.
Mitigation:** Measures taken in advance of a disaster aimed
at decreasing or eliminating its impact on society and
the environment.
Peak flow:** The largest flow rate during a given flood (synonym:
peak discharge).
Preparedness:** Activities designed to minimize loss of life
and damage, to organize the temporary removal of
people and property from a threatened location and
facilitate timely and effective rescue, relief and
rehabilitation.
Prevention:** Encompasses activities designed to provide
permanent protection from disasters. It includes
engineering and other physical protective measures, and
also legislative measures controlling land use and urban
planning.
Probable maximum flood (PMF):** The largest flood that
could conceivably occur at a given location.
Probable (possible) maximum precipitation (PMP):*** The
theoretically greatest depth of precipitation for a specific
duration which is physically possible over a
particular drainage area at a certain time of the year.
Rainfall-runoff model:** A mathematical model that predicts
the discharge of given river as a function of rainfall.
Rating curve:* Curve showing the relation between stage
and discharge of a stream at a hydrometric station. If
digitized, it is a rating table.
Recurrence interval:Seemean return period.
Relief:** Assistance and/or intervention during or after disaster
to meet life preservation and basic subsistence
needs. It can be of emergency or protracted duration.
Risk:** Expected losses (of lives, persons injured, property
damaged, and economic activity disrupted) due to a
particular hazard for a given area and reference period.
Based on mathematical calculations, risk is the product
of hazard and vulnerability.
Stage:* Vertical distance of the water surface of a stream,
lake, reservoir (or groundwater observation well) relative
to a gauge datum.
Storm surge:** A sudden rise of sea level as a result of high
winds and low atmospheric pressure (also called storm
tide, storm wave or tidal wave).
Tropical cyclone:* Cyclone of tropical origin of small diameter
(some hundreds of kilometres) with minimum
surface pressure in some cases less than 900 hPa, very
violent winds, and torrential rain; sometimes accompanied
by thunderstorms.
Tsunami:* Great sea wave produced by a submarine earthquake
or volcanic eruption.
Vulnerability:** Degree of loss (from 0 per cent to 100 per cent)
resulting from a potentially damaging phenomenon.
Watershed:** All land within the confines of a topographically
determined drainage divide. All surface water
within the watershed has a common outlet (synonym:
catchment, drainage basin).
Water surface profile: The elevation of the water surface
along the river centreline, usually plotted along with the
elevation of the channel as a function of river distance
from a tributary junction.
T-year flood: In each year, there is a 1/T probability on average
that a flood of magnitude Q T or greater will occur.
The 100-year flood is a commonly applied T-year flood
where T is 100 years.
3.13 REFERENCES
American Society of Civil Engineers and Water Pollution
Control Federation (ASCE and WPCF), 1970: Design
and Construction of Sanitary and Storm Sewers, ASCE
Manuals and Reports of Engineering Practice No. 37 or
WPCF Manual of Practice No. 9, ASCE, New York or
WPCF, Washington, DC, 332 pp.
Aysan, Y.F., 1993: Vulnerability Assessment, in Natural
Disasters: Protecting Vulnerable Communities, Thomas
Telford, London, pp. 1-14.
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