FLOOD MAPPING Menaxhimi i rezikut te permbytjeve Objektivat Gjenerale
Jan 20, 2016
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.