FLOOD MAPPING

Menaxhimi i rezikut te permbytjeve

Objektivat Gjenerale

General Objectives

1. Protect people and goods2. Preserve river capacity and flood plants3. Conserve ecological equilibrium

To reach these objectives, a regulation of land use in the floodplain is necessary:

– Forbidding new construction in high risk areas,

– Controlling urban extension in floodplain,

– Limiting embankment to minimum.

Example of flood risk mapping

• Zone 1 - Little / no risk• Zone 2 - Low to Medium risk (light blue)• Zone 3 - High risk (dark blue)

Principe of flood risk analysis

– Flood hazard assessment: three hydraulic parameters considered

1. Water depth,2. Flow velocity,3. Duration of inundation

Flood risks analysis

Flood hazard classification

Depth Velocity

Low velocity (Plain flood)

Medium velocity

High Velocity(Flash flood)

Depth < 0.5 m Moderate Moderate Moderate to high

0.5m < depth > 1.0m

Moderate High High

Depth >1.0m High High High

Flood risk assessment

Vulnerability classification by distinguishing

urban / non urban areas

Flood risk mapping

Flood plain Urban areas

High flood hazard High risk High risk

Moderate flood hazard

Low risk High risk

Flood hazard + vulnerability,

Vulnerability mapping

EXAMPLE Land use regulation

Nature of time construction

TypeNon

urban Zone

Urban Zone

Moderation hazard

High flood hazard

Habitation, Industries, activities

New X Prescriptions X

Reconstruction X X X

Extension Prescriptions Prescriptions Prescriptions

Modification Prescriptions Prescriptions Prescriptions

Public equipment All kinds Prescriptions Prescriptions Prescriptions

CampingNew X X X

Extension X X X

OthersNew X X X

Extension X Prescriptions X

Modification Prescriptions Prescriptions Prescriptions

Where are we now ?

Methodology

Flood

Flood Hazard / Flood Risk

• Different scales

– Preliminary flood risk assessment• Drini River Basin

– Local flood risk map• Pilot area : Skenderaj

Preliminary flood risk assessment DATA GATHERING AND PROCESSING

• Topographical and hydrological data

– SRTM 90 DEM– Contour lines (10m)– Historic floods etc.

• Problems and accuracy– SRTM DEM : 90m x 90m, dZ~10m – Shifting between different maps

DEM from contour lines

SRTM DEM

Shifting between different maps

What are we going to do ?

Improving preliminary delineation of flood areas

– Send questionnaires for the most sensitive towns

– Process with available satellite imagery

– For sensitive areas assess flood hazard with simplified hydraulic calculations and fields visits

– Georeferencing all data

Remember past flooding events (2004-2008)

Skenderaj flooding zone

Local flood risk map Pilot area: Skenderaj

Work completed:• Field visits • Questionnaire prepared • TOR for topographic survey

Next steps• Hydraulic modelling• Flood risk mapping• Discussing about a pilot flood risk management plan

A quick presentation of

the technology

Floodplain Mapping Approach

Watersurfaceprofiles

ArcGIS

Geometricdata

ParametersSchematic

Flowdischarge

Hydrology Hydraulic model

ArcGIS

HydraulicHydrology

Floodplain Mapping Approach

ArcGISInput Data

DEM

HydrologyFlood

discharge

HydraulicWater

surfaceprofiles

ArcGISFlood

plain maps

Flowdischarge

Geometricdata

ParametersSchematic

ArcGIS

HydraulicHydrology

Hydrology

Hydrology

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Digital Terrain Model: DTM

ArcGIS

HydraulicHydrology

• Observed points and break lines for constructing

a triangular irregular network (TIN).

•TIN components:- nodes- edges- triangles

Triangular Irregular

Network : TIN

ArcGIS

HydraulicHydrology

DTM -

• 3D display

of a TIN.

DTM – TIN 3 D display of topography

ArcGIS

HydraulicHydrology

DTM – TINDisplay of buildings

• Embedding Buildings into the TIN.

ArcGIS

Hydraulic

Hydrology

Topographic survey:

Cross Sections

• Stream centerline.• Banks.• Flow paths.• Cross sections.

ArcGIS

HydraulicHydrology

Hydraulic Modelling

• stream geometry.

• Cross-sections extracted from the TIN.

ArcGIS

HydraulicHydrology

Hydraulic Modelling

• Water surface elevations.

ArcGIS

HydraulicHydrology

Floodplain Mapping

• Floodplain

ArcGIS

HydraulicHydrology

Floodplain Mapping

• 2-D floodplain animation.

ArcGIS

HydraulicHydrology

Floodplain Mapping

• 3-D floodplain animation.