FLOODING: AN ISSUE TO HANDLE IN FAST GROWING COUNTRIES 1. The - - PowerPoint PPT Presentation

MYANMAR – ITALIAN TECHNICAL SYMPOSIUM

FLOODING: AN ISSUE TO HANDLE IN FAST GROWING COUNTRIES

• 1. The problem of flooding
• 2. Factors affecting flooding hazards
• 3. Approach to flood mitigation: structural and non

structural approache and measures

• 4. Virtuous international models:
• SUDS (Sustainable Urban Drainage System)
• BMP (Best Management Practices)
• LID (Low Impact Development)
• Dott. Eng. Beatrice Majone

MYANMAR – ITALIAN TECHNICAL SYMPOSIUM

• 1. The problem of flooding: numbers

By 2050, flood damage in the world’s coastal cities is expected to reach US$1 trillion a year as sea levels rise and global warming triggers more extreme weather River flooding will affect more people and cause significantly more damage by 2030, as climate change and socioeconomic development accelerate. In South Asia alone, an estimated 15 million will be affected. One of the hardest‐hit areas is predicted to be South Asia, a region where more than 9.5 million people are already being affected every year by floods. Last year alone, unusually heavy monsoon rains triggered floods in India and Pakistan claiming more than 500 lives.

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• 1. The problem of flooding: Myanmar

Flood of 01 July 2016 - Myanmar Rakhine State 24,306 people displaced : Minbya (13,123), Ann (4,659), Mrauk-U (3,696) and Kyauktaw (2,828 ) Water extents on 2,549 Km ter extents on 2,549 Km² ² corresponding corresponding to to ~8% of the total area of Rakhine State ~8% of the total area of Rakhine State UNITA UNITAR-UN R-UNOSAT, AT, using Sentinel-1 SAR imag using Sentinel-1 SAR image of 14 July 2016: Rakhine State e of 14 July 2016: Rakhine State Affected transportation network: ~ 230 Kms of Rakhine State roads affected ฀ - ~ 60 Km of major roads. ฀ - ~172 Km of other types of roads.

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• Small-scale catchment
• Steep slope – short flood wave transit time
• High flow velocities – destructive forces
• Entrains sediment transport and debris flow

Flood 2002 Valtellina-Italy

The worst for fatalities !!!

• 2. Factors affecting flooding hazards:flash floods

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• Involve high density cities and turistic

cities

• Although the sea level does not grow a

lot both the natural drainage system and the urban drainage system can not discharge the flow; backup effect

• Cause sea pollution due to bad

functioning of combined sewer systems

Flood Schiavonea Marina - Italy

• 2. Factors affecting flooding hazards:coastal floods

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• Not correct design of drainage

system or combined sewer system

• Not proper maintenance of

drainage system or combined sewer system

• River flood or coastal flood
• 2. Factors affecting flooding hazards:urban floods

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1. Natural Environment Characteristics

• Basin area/shape/topography
• Drainage area affects discharge
• Regular shaped basins are more flood

prone than longer, narrower basins

• Steeper slopes are more flood prone
• Geology and soil features
• Hydro-geological conditions
• Vegetational features

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2. Built‐environment Characteristics

– Urbanization increases total impervious area – Decrease infiltration, increase runoff –Shorter time of concentration (Rain Run

• ff)

– Wetland alteration

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• 1. The problem of flooding: what exactly

is flood risk ? R = P x V

• If one of these elements is zero there is no flood risk
• The decision makers must know both the value of

the two elements that quantify the risk

• Risk of flooding is not an abstract concept: is a number

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• 3. Approach to flood mitigation:

Water Framework Directive

• Directive of the European Parliament and of the Council
• n the assessment and management of flood risk
• Art. 1: …to establish a framework for the assessment and management
• f the flood risk, aiming at the reduction of the adverse consequences for

human health, the environment, cultural heritage and economic activity associated with floods in the Community. The Directive requires: Preliminary risk assessment Flood hazard mapping and flood risk mapping Flood risk management plans

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3.Approach to flood mitigation:

structural and non structural measures

• Structural:

 Aimed at flood protection  Permanent  Hydraulic Engineering works

• Non-Structural

 Considered soft measures  Focus on changing the natural conditions of the catchment, the channel or the flood plain  Aimed at monitoring, detecting and forecasting floods

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Structural Measures: Levees

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Structural Measures: Detention basins

Water levels Flow directions Water velocity

Hydrodinamic 2D model of the poject solution

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Non Structural Measures

• Environmentally sensitive area protection

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• 4. Virtuous international models:
• SUDS (Suastainable Urban

Drainage System)

• BMP (Best Management Practices)
• LID (Low Impact Development)

MYANMAR – ITALIAN TECHNICAL SYMPOSIUM

SUDS (Suastainable Urban Drainage System)

Sustainable Urban Drainage Systems a new approach to water management in urban area.

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THANKS FOR YOUR ATTENTION