Post-fire flood hazard and risk assessment in Neapolis, Laconia

Postgraduate Thesis uoadl:1318894 446 Read counter

Unit:
ΠΜΣ Στρατηγικές Διαχείρισης Περιβάλλοντος, Καταστροφών και Κρίσεων
Library of the School of Science
Deposit date:
2016-10-04
Year:
2016
Author:
Μήλιος Δημήτριος
Supervisors info:
Λέκκας Ευθύμιος Καθηγητής (Επιβλέπων) , Νάστος Παναγιώτης Καθηγητής, Μερτζάνης Αριστείδης Αναπληρωτής Καθηγητής
Original Title:
Μετα-πυρική διαχείριση πλημμυρικής επικινδυνότητας στην περιοχή της Νεάπολης, Λακωνίας
Languages:
Greek
Translated title:
Post-fire flood hazard and risk assessment in Neapolis, Laconia
Summary:
On July 17, 2015 a forest fire that broke out in the southern part of Epidavros
Limira peninsula (Laconia, southeastern Peloponnese) expanded rapidly due to
strong winds blowing in the area and raged out of control for two days,
inducing damage to agriculture, livestock farming, buildings and infrastructure
and causing one fatality. This forest fire is one of the largest in Greece in
recent years. The Voies Municipal Unit of the Monemvasia Municipality (Laconia
Prefecture) was most affected with Neapolis town and Mesochori, Faraklo, Lachi
and Agios Nikolaos villages suffering considerable damage. Based on the fire
damage assessment performed by the Monemvasia Municipality, the fire-affected
area has size of about 60 km2, 25 km2 of forest and 35 km2 of cultivation land
were burned in an area extending from the eastern coastal area of Vatika Bay to
the main drainage divide along the central mountainous part of the Epidavros
Limira peninsula. Moreover, 10 houses were totally destroyed and more than 150
were partially affected. 100 farm warehouses were totally destroyed, 120000
olive trees and 600 beehives were burned. Infrastructures including the
electricity and water supply networks suffered considerable damage.
Immediately after the fire and during the disaster stage, a field
reconnaissance team including a large number of experts in the management of
environment, disasters and crises visited the affected area in order to
evaluate the impact of the fire on the natural environment and to provide
scientific, technical and humanitarian assistance to the local authorities and
residents. Among other activities, the team developed and conducted an applied
research program and the respective plan for the integrated management of the
geo-environmental impact of the fire and the immediate restoration of the
fire-affected area.
As far as the post-fire flood hazard and risk assessment is concerned, the
study used detailed topographic data to developed a 10x10m digital elevation
model of the study area and a very high resolution (0.5m) Worldview-2 image to
map all elements relevant to the hydraulic processes, including buildings,
obstructions to flow, drainage network, land-cover, manning roughness
coefficients, as well as bridges and culverts. Electronic rangefinders with
accuracy of 1cm were used to measure dimensions of critical cross sections
along drainage routes of the floodplain, which later were used as input in the
hydraulic model. HEC-RAS 1-D hydraulic modelling software (Brunner, 1995) was
used to simulate water flow across the floodplain. The basic scenario used was
the one of 50 years return period, extracted based on the curve number
rainfall-runoff methodology (NRCS, 2004).
Simulation results visualized the extent of flood water for the 50 years (or 2%
probability) scenario, across the Neapolis floodplain, as it overflowed Xerias
torrent, showing that a large part of the coastal area of the town is under
risk of flooding. Water flow depth was also visualized with higher values found
along the torrent, as expected, but also at specific locations along the coast,
where infrastructure development and probably old sand dune formations has
created a minor rise in elevation that clearly affect drainage locally.
This study proposes also a series of structural and non-structural measures,
designed and placed strategically to reduce vulnerability by protecting
property and infrastucture and restricting the activity of individuals in high
flood risk parts of the study area. The measures are also designed to reduce
erosion and transportation of debris by the torrents downstream and decrease
expected peak flows in the post-fire environment.
Keywords:
Neapolis, Risk Assessment, Flood Hazard, Xerias, Laconia
Index:
Yes
Number of index pages:
11
Contains images:
Yes
Number of references:
47
Number of pages:
81
File:
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document.pdf
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