Terrain Based Flood Inundation mapping

David TarbotonUtah State University

dtarb@usu.edu

Acknowledgements: David Maidment, Nazmus Sazib, Xing Zheng, Solomon Vimal, US Army Corps of Engineers (SWWRP, ERDC, HEC), National Science Foundation (XSEDE, CyberGIS, OpenTopography, CI-WATER), William Penn Foundation (Stroud Water Center Model My Watershed)

http://hydrology.usu.edu/taudem

Concept

• WRF + NOAH-MP + RAPID/SPRNT produce flows at reach scale

• Need a way to obtain reach level hydraulic properties for inputs to these models

• Need a way to map from reach scale stage to flood inundation depth

• Exploit high resolution topography and 1:1 relationship between reaches (Hydro) and Catchments (Ele)

Height above the nearest stream (HANS) flood mapping

• Each stream reach has a water depth hw (e.g. from SPRNT)

• Each stream reach has an ID• Each grid cell has the ID of the reach it connects to and

the height above the nearest stream hs

• Evaluate approximating inundation using hw-hs If(hw(id) > hs(id))

Inundation depth = hw(id) - hs(id)

ElseInundation depth = 0

Mapping Flood Extent and Depth by Reach

Flowlines

Catchments

Height above stream(relative elevation of land surface cell above cell in stream to which it flows)

Inundation map

Reach Scale Flood Depth

Comid Depth (ft)5781365 8

5781381 9

5781405 10

5781401 15

5781399 14

5781383 12

5781933 11

Height above the nearest stream background

TauDEM (http://hydrology.usu.edu/taudem)Tesfa, T. K., D. G. Tarboton, D. W. Watson, K. A. T.

Schreuders, M. E. Baker and R. M. Wallace, (2011), "Extraction of hydrological proximity measures from DEMs using parallel processing," Environmental Modelling & Software, 26(12): 1696-1709, http://dx.doi.org/10.1016/j.envsoft.2011.07.018.

Nobre, A. D., L. A. Cuartas, M. Hodnett, C. D. Rennó, G. Rodrigues, A. Silveira, M. Waterloo and S. Saleska, (2011), "Height Above the Nearest Drainage – a hydrologically relevant new terrain model," Journal of Hydrology, 404(1–2): 13-29, http://dx.doi.org/10.1016/j.jhydrol.2011.03.051.

Nobre, A. D., L. A. Cuartas, M. R. Momo, D. L. Severo, A. Pinheiro and C. A. Nobre, (2015), "HAND contour: a new proxy predictor of inundation extent," Hydrological Processes, http://dx.doi.org/10.1002/hyp.10581.

Comid H A R P T V Ab As

5781175 3

5781175 4

Wetted Bed Area

Reach Scale River Hydraulic Properties

L

As

Ab V

T

PA

𝐴=𝑉𝐿

T

P

Cross Section Area

Wetted Perimeter

Top Width

h

Surface Area

Volume

Depth

• A table with reach hydraulic parameters as keyed to hydrography

• Derived from DEM, LIDAR or HEC RAS cross sections

R Hydraulic Radius

SPRNT Model – flow and water depth on large networks

Very Large Scale Integrated (VLSI) design of computer chips – solve 100 million equations each night to check on effects of design changes on electricity flow in chip

Dynamic wave routingCompute water flow by analogy with electricity flow in chips

Open source code in Github

Ben Hodges, Slide from David Maidment

http://hydrology.usu.edu/taudem/

TauDEM • Stream and watershed delineation• Multiple flow direction flow field• Calculation of flow based derivative surfaces• MPI Parallel Implementation for speed up and large

problems• Open source platform independent C++ command line

executables for each function• Deployed as an ArcGIS Toolbox with python scripts that

drive command line executables

D

Representation of Flow Field

D8

6756

5248

50.030

5267

Steepest single

direction

Tarboton, D. G., (1997), "A New Method for the Determination of Flow Directions and Contributing Areas in Grid Digital Elevation Models," Water Resources Research, 33(2): 309-319.)

Flowdirection.

Steepest directiondownslope

1

2

1

234

5

67

8

Proportion flowing toneighboring grid cell 3is 2/(1+

2)

Proportionflowing toneighboringgrid cell 4 is

1/(1+2)

TauDEM Parallel Approach

• MPI, distributed memory paradigm

• Row oriented slices• Each process includes one

buffer row on either side• Each process does not

change buffer row• Improved runtime

efficiency• Capability to run larger

problems

TauDEM generalized terrain flow surfaces

Dinfinity contributing area Distance to stream (vertical) Decaying accumulation

hs hr

vr

vs

Point of interest

Ridge

pr

psss

sr

hs hr

vr

vs

Stream

pr

psss

sr

Distance Down and Distance Up

Generalized Flow Accumulation (“Flow Algebra”)

Pki Pki Pki

i

Flow Accumulation

𝐴𝑖=𝑤𝑖∆+ ∑{𝑘 :𝑃 𝑘𝑖>0 }

𝑃𝑘𝑖𝐴𝑘

Generalized Flow Accumulation (upslope)

¿Generalized Flow Accumulation (downslope)

¿

TauDEM model for drop to stream

• Could use D8 instead of Dinfinity• Could use Euclidean distances• Premised on good elevation model

and consistent stream raster• Can be applied separately by

catchment • parallelism• Incremental refinement of DEM

i

PikPik

h 𝑖=𝑑 (𝑖 ,𝑘)+∑ 𝑃 𝑖𝑘h𝑘

h 𝑖=0 for i on streamraster

𝑑 (𝑖 ,𝑘)=zi− zk for vertical drop

Drop to Stream from TauDEM for Onion Creek near Austin Texas

1/3 arc second NED DEM

0

1 0 1 2

2 1 0 1 2 3

3 1 0 0 2 2 4

3 1 0 1 1 0 1 2 5

2 1 0 1 2 1 0 1 5

2 0 1 2 2 1 0 3 4

2 0 1 3 3 2 1 0 1 4

2 2 2 3 4 3 2 1 2 4

3 3 2 3 4

Mapping from height above nearest stream to flood extent

1

1 1 1 1

1 1 1 1 1 1

2 2 2 3 3 3 3

2 2 2 2 3 3 3 3 3

2 2 2 2 3 3 3 3 3

2 2 2 2 3 3 3 3 3

2 2 2 2 3 3 3 3 3 3

2 2 2 2 3 3 3 3 3 3

2 3 3 3 3

Reach and Watershed id Height above nearest stream raster hshw(1) = 1.5

hw(2) = 2.5 hw(3) = 3.5

hw=8 ft hw=9 ft

hw=11 ft

hw=12 ft

hw=14 ft

hw=10 ft

hw=15 ft

Reach based height above nearest stream flood map example

Terrain based derivation of “reach scale” hydraulic properties

For each CatchmentFor each height hIdentify cells where hs < h

Bed Area

Surface area

Single Cell Plan Area =dx * dy

Volume = T

PA

𝐴=𝑉𝐿 Cross Section Area

P Wetted Perimeter

T Top Width

Wetted Bed Area L

As

Ab

V

Surface Area

Volume

R Hydraulic Radius

Approximates each cell as sloping plane

Reach Hydraulic Properties Example1 m inundation 3 m inundation

Height (m) As (m2) Vol (m3) Ab L (m) A=V/L (m2) P=Ab/L (m) T=As/L (m) R=A/P (m)1 129878 79466 129948 2975 26.7 43.7 43.7 0.6123 319877 530378 320414 2975 178.3 107.7 107.5 1.655

Terrain Approximated Reach Average Hydraulic Properties

0 1 2 3 4 5

02

46

81

0

R (m)

h (

m)

50 100 200 300

02

46

81

0

T (m)

h (

m)

50 100 200 300

02

46

81

0

P (m)

h (

m)

0 500 1000 1500

02

46

81

0

A (m)

h (

m)

Need to evaluate in Hydraulic Model (e.g. SPRNT)

Hydraulic Radius Wetted Perimeter

Cross-sectional Area

Top Width

Terrain Catchments reconciled with NHDPlus by “seeding” with stream sources

• The approach is predicated on a DEM stream raster consistent with DEM and NHDPlus reaches

• Here stream raster computed using weighted flow accumulation starting from source points

DEM Flowlines challenged by road barriers

Need for hydrography conditioned DEM

DEM Conditioning Options

• Fill pits • Carving• Optimal pit remove• Punch through using

flowlines• Geonet

7 7 6 7 7 7 7 5 7 7

9 9 8 9 9 9 9 7 9 9

11 11 10 11 11 11 11 9 11 11

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15 11 11 11 11 17 17 14 17 17

15 15 15 15 15 18 18 15 18 18

Pit Filling

7 7 6 7 7 7 7 5 7 7

9 9 8 9 9 9 9 7 9 9

11 11 10 11 11 11 11 9 11 11

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13 12 7 12 13 13 13 11 13 13

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15 15 15 15 15 18 18 15 18 18

Pits Pour Points

Original DEM Pits Filled

Increase elevation to the pour point elevation until the pit drains to a neighbor

7 7 6 7 7 7 7 5 7 7

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14 7 6 11 14 14 14 6 14 14

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Carving

7 7 6 7 7 7 7 5 7 7

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13 12 7 12 13 13 13 11 13 13

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15 15 15 15 15 18 18 15 18 18

Pits Carve outlets

Original DEM Carved DEM

Lower elevation of neighbor along a predefined drainage path until the pit drains to the outlet point

Filling

CarvingMinimizing Alterations

Optimally adjusted

Minimizing DEM Alterations

7 7 6 7 7 7 7 5 7 7

9 9 8 9 9 9 9 7 9 9

11 11 10 11 11 11 11 9 11 11

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Pits

Original DEM

7 7 6 7 7 7 7 5 7 7

9 9 7 9 9 9 9 7 9 9

11 11 7 11 11 11 11 9 11 11

12 12 7 12 12 12 12 10 12 12

13 12 7 12 13 13 13 11 13 13

14 7 7 11 14 14 14 12 14 14

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15 15 15 15 15 18 18 15 18 18

Carved

Filled

Decompose computation by catchmentsor River Corridor

• Parallel computation• High resolution in some areas• Incremental improvement

Conclusions• NFIE presents a use case that demands consistency

between elevation and hydrography information at high resolution

• The height above nearest stream approach suggested as way to rapidly approximate real time flood inundation

• Includes an approach to approximate reach scale hydraulic properties

• Need to evaluate versus more detailed (e.g. HEC-RAS) hydraulic model

• Need to evaluate with HRT (LIDAR) vs general (NED) DEM as input

• Need to align and reconcile elevation and hydrography

Are there any questions ?

AREA 1

AREA 2

3

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