Large scale floodplain mapping Nardi et al. 1/26

American Geophysical Union (AGU) 2013 Fall Meeting

December 11th, 2013

Session H044. Hydrological change and water systems: feedbacks, prediction, and experimental management

Large scale floodplain mapping using a hydrogeomorphic method

Nardi F.1,*, Yan K.2, Grimaldi S.3, Di Baldassarre G.2

1. University for Foreigners of Perugia, Italy2. Unesco IHE, Delft, The Netherlands3. Tuscia University of Viterbo, Italy

Session H044. Hydrological change and water systems

• Floodplains

• Aim of this work

• DEM-based Hydrogeomorphic

Floodplain Algorithm

• Large scale floodplain analysis

• Applications: The Po and Tiber basin in

Central Italy, the Zambesi basin in

Southern Africa

OUTLINES

Large scale floodplain mapping Nardi et al. 2/26

Session H044. Hydrological change and water systems

FloodplainsRiver basin (landscape) features t- hat are clearly distinguishable from surrounding hillslopes for the different geomorphologic, hydrologic, biogeochemical, ecological properties - representing the trace/effect of ages of water-driven erosion and depositional processes.

Parana floodplain, Brazil

Tiber floodplain, Italy

Rio Salado floodplain, USA

River valleys/Valley Bottoms are the regions where humans have historically developed and keep developing

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River Basins = Floodplains + Hillslopes

FLOODPLAIN

HILLSLOPES

GIS DEM-based hydrologic processing

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Session H044. Hydrological change and water systems

Floodplain topography intrinsically contains information on the hydrogeomorphic signature of past erosional and depositional processes. Digital Topography contains significant information on the floodplain-related physical phenomena

Aim of this work

Investigating on a tool

for large scale

hydrogeomorphic

floodplain

delineation by

looking into

global topography

Water-driven erosion and deposition processes shape

river valleys

DEM implicitly contains the floodplain information

FLOODPLAIN

HILLSLOPES

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Session H044. Hydrological change and water systems

Digital Elevation Models

http://www2.jpl.nasa.gov/srtm/

NASA ASTER/SRTM (30/90 m of resolution) since 2000

Commercial Products (Digital Globe, Quickbird, Ikonos etc)

Landsat and Corine databases since 1975

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Session H044. Hydrological change and water systems

Floodplain delineation algorithm

Bhowmik, N. G. (1984), Hydraulic geometry of floodplains, J. Hydrol., 68, 369 – 374.

Nardi, F., E. R. Vivoni, and S. Grimaldi (2006), Investigating a floodplain scaling relation using a hydrogeomorphic delineation method, Water Resour. Res., 42.

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Session H044. Hydrological change and water systems

Step 1. Floodplain main direction and cross sections

Nardi F., Vivoni E. R., Grimaldi S. (WRR, 2006)

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Session H044. Hydrological change and water systems

Step 2. Inundation depth

Nardi F., Vivoni E. R., Grimaldi S. (WRR, 2006)

River network geomorphic propertiesClimatic conditions (Rainfall)

Local hydrogeomorphic propertiesOf the floodplain (fluvial) cross section

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Session H044. Hydrological change and water systems

Step 2. Inundation depths

Nardi F., Vivoni E. R., Grimaldi S. (WRR, 2006)

b

Variable floodplain flow depths using a scaling (Leopold) law

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Session H044. Hydrological change and water systems

Leopold parameters are estimated

Step 3. Floodplain delineation

Nardi F., Vivoni E. R., Grimaldi S. (WRR, 2006)

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Session H044. Hydrological change and water systems

Step 4. Sample application

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Session H044. Hydrological change and water systems

Nardi et al (Irrigation and Drainage, 2013)

How do the hydrogeomorphic floodplain behave as respect to standard flood/inundation maps?

Step 4. Sample application on a large basin

Nardi et al (Irrigation and Drainage, 2013)

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Session H044. Hydrological change and water systems

Large scale floodplain parsimonious and computational efficient analysisImposing Leopold law scaling parametersand exploring the floodplain method behaviorFixing the intercept and varying the slope

and viceversa

64 Combinationsa = [0.00005 to 0.002]

b = [0.3 to 0.4]

b

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Session H044. Hydrological change and water systems

Po river basin (North Italy)

Area 75,000 km2

Channel flow depths: up to 44 m

Stream network source contrib. area: 500 km2

Floodplain area: 5178 km2 to 14976 km2

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Session H044. Hydrological change and water systems

Po river basin (North Italy)

500 yrs Flood/Inundation maps -> 10,300 km2 Lake areas: 1000 km2

Floodplain area: 5178 km2 to 14976 km2

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Session H044. Hydrological change and water systems

Po river basin (North Italy)Comparing the hydrogeomorphic

floodplain with geomorphologic floodplain

interpretation

Sedimentary Geology (2012) Floods, floodplains, delta plains A satellite imaging approach,

James P.M. Syvitski et al.

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Session H044. Hydrological change and water systems

Tiber river basin (Central Italy)

Area 17,500 km2

Channel flow depths: up to 25 m

Stream network source contrib. area: 500 km2

Floodplain area: 760 km2 to 1455 km2

200 yrs flood maps: 436 km2

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Session H044. Hydrological change and water systems

Tiber river basin (Central Italy)

City of Rome

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Tiber river basin

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Tiber river basin

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Tiber river basin

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Session H044. Hydrological change and water systems

Tiber river basin

HYDROGEOMORPHIC FLOODPLAIN

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Hydrologic-Hydraulic flood maps

Zambesi river basin (Southern Africa)Area 1,390,000 km2

Stream network source contrib. area: 500 km2

Floodplain area: 37,250 km2

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Session H044. Hydrological change and water systems

Zambesi river basin (Southern Africa)

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Session H044. Hydrological change and water systems

Discussion• The automated algorithm accurately captures the

hydrogeomorphic floodplain information from the STRM 90m DEM

• The behavior of the hydrogeomorphic floodplain is investigated by comparing model performances as respect to standard flood maps, demonstrating the capability of looking into DEM data, but for model validation geomorphologic studies for floodplain interpretation shall be considered

• Forcing the model imposing a wide range of Leopold law parameters for scaling channel/floodplain flow depths the potential for the model to automatically delineate the floodplain for large river basins across the globe is investigated

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