urban erosion potential risk mapping with gis · 1. investigate the important parameters of soil...

Urban Erosion PotentialRisk Mapping with GIS

ESRI Water ConferenceSan Diego, CA Jan 29-Feb 1, 2018

Dr. Randy Dymond, PE, F.ASCE, D.WRECo-investigators: Amanda Weikmann, MS StudentDr. Clay Hodges, PE – Research Asst Prof

OUTLINE

1.Introduction

2.Methods

3.Results

4.Conclusion

“The Nation that destroys its soil destroys itself”

Franklin D. Roosevelt, 1937

2

HISTORY OF SEDIMENT REGULATIONS

1933

1973

1972 1987

Soil Erosion Service (SES)Then SCS, NRCS

Maryland Sediment Control Regulations

The Clean Water Act(CWA)

Virginia Erosion &Sediment Control Law

(VESCL)

The Water Quality Act(WQA)

1938

Virginia Soil &Conservation District Law

1948

The Federal WaterPollution Control Act

1970

Maryland Sediment Control Law

1957

Introduction | Methods | Results | Conclusion

3

SEDIMENTATION AND EROSION

http://catawba.naturalresources.anthro-seminars.net/sedimentation/

https://earthobservatory.nasa.gov/IOTD/view.php?id=89003

Deposition• Alter channel dimensions• Landlock ports• Smother aquatic organisms• Deposit bound pollutants

Suspension• Alters aesthetics (turbidity)• Blocks sunlight in water column• Transport bound pollutants


4

STORMWATER RUNOFF REGULATIONS & CONTROL

https://www.epa.gov/npdes/stormwater-discharges-municipal-sources


He, J. (2017). Sedimentation [Lecture notes]. Retrieved from https://canvas.vt.edu

5https://www.ofallon.org/stormwater/pages/stormwater-facts-information

SOIL EROSION PROCESSESIntroduction | Methods | Results | Conclusion

Splash Erosion

Transport Erosion

6

SOIL EROSION PROCESSESIntroduction | Methods | Results | Conclusion

Splash Erosion

Transport Erosion

7

https://www.slideshare.net/AmrithaKTK/soil-profile-soil-erosion-soil-conservation-control-on-floods-69527117

http://passel.unl.edu/Image/siteImages/UrbanRillErosion‐NRCS‐LG.jpg

Sheet Erosion

Rill Erosion

SOIL EROSION MODELSIntroduction | Methods | Results | Conclusion

Figure from Mattheus et al., 2013

Figure from DeRoo et al., 1994

Erosion Map output from LISEMErosion Map output from USLE

8

USLE (Wischmeier and Smith, 1978)

LISEM (DeRoo et al., 1994)

OBJECTIVESIntroduction | Methods | Results | Conclusion

9

1. Investigate the important parameters of soil erosion

2. Develop a method for determining Erosion Potential (EP) through GIS and computational analysis

3. Interpret results of the methodology

4. Generate final erosion potential risk maps for Central Stroubles watershed in the Town of Blacksburg, VA

5. Create a procedure for municipal governments to produce EP risk maps

IMPORTANT PARAMETERSIntroduction | Methods | Results | Conclusion

10

From Literature:• Runoff Volume• Slope• Land Cover• Soil Erodibility• Rainfall Intensity

IMPORTANT PARAMETERSIntroduction | Methods | Results | Conclusion

11

Site Component• Runoff Volume (VR )• Local Slope (SL )• Land Cover (LC)• Soil Erodibility (Kf )

Transport Component• Distance to nearest stormwater

conveyance point (D)• Slope along surface flow travel

path to nearest stormwater conveyance point (SA )

Rainfall Intensity Excluded• Homogenous across watershed • Relative EP ranking

EROSION POTENTIALIntroduction | Methods | Results | Conclusion

EP = Erosion potentialVR = Accumulated runoff volumeSL = Local slope of the cell LC = Land cover Kf = Soil erodibility D = Distance to inletSA = Average slope to inlet

Site Component Downstream TransportComponent

Minimum Score Maximum ScoreSite Component 1 10,000

Downstream Transport Component

1 100

Erosion Potential 2 10,100

12

CENTRAL STROUBLES WATERSHEDIntroduction | Methods | Results | Conclusion

Case Study: Central Stroubles10 x 10 meter raster analysis(smaller gave major runtime problems)

Land Cover Types• Residential• Commercial• Urban

Data Used• 2-ft Contours lines to DEM• Stormwater Infrastructure points• Detailed Land Cover Database

(DLCD)• Web Soil Survey (WSS) polygon• National Hydrography Database

(NHD) Flowlines • Aerial Imagery 13

Old Blacksburg High School

WestviewCemetery

DEM VS WATERSHED DELINEATIONIntroduction | Methods | Results | Conclusion

14

Digital Elevation Model• 2 ft contours• Not infrastructure

corrected

Watershed Delineation• Infrastructure corrected

Issues with DEM crossing Watershed delineation when finding flow paths

DEM VS WATERSHED DELINEATIONIntroduction | Methods | Results | Conclusion

15

Digital Elevation Model• 2 ft contours• Not infrastructure

corrected

Watershed Delineation• Infrastructure corrected

Issues with DEM crossing Watershed delineation when finding flow paths

EVALUATING LAND SURFACE EROSIONIntroduction | Methods | Results | Conclusion

16

Stream Locations Excluded• Streambank erosion not

addressed by this procedure

• Based on non-weighted flow accumulation

• Threshold values established by NHD flowlines, aerial photo and channel cross sections

SITE COMPONENT: PARAMETERSIntroduction | Methods | Results | Conclusion

17

Runoff Volume, VRRelative Rank

Local Slope, SLAbsolute Rank

Soil Erodibility, KfAbsolute Rank

Land Cover, LCAbsolute Rank

Rank 2 Yr. Runoff Volume(ft3)

1 4422 1,1733 2,3454 4,3115 7,0626 10,7577 15,7898 22,8599 33,916

10 48,898


18





Rank 2 Yr. Runoff Volume(ft3)

1 4422 1,1733 2,3454 4,3115 7,0626 10,7577 15,7898 22,8599 33,916

10 48,898

Rank Local Slope

(degrees)

1 6

2 12

3 174 21

5 276 31

7 358 39

9 4210 >= 45


19





Rank Land Cover

1 Impervious2 ~ not assigned~3 Dense Forest4 Light Forest/Tree Canopy5 Brush/Bush6 Open Space (Lawn)7 Gravel8 Light Bush/Dirt/Mulch9 ~ not assigned~

10 Dirt


20





Rank Land Cover

1 Impervious2 ~ not assigned~3 Dense Forest4 Light Forest/Tree Canopy5 Brush/Bush6 Open Space (Lawn)7 Gravel8 Light Bush/Dirt/Mulch9 ~ not assigned~

10 Dirt

Rank Soil Erodibility∗ ∗

∗ ∗

1 0.072 0.143 0.214 0.285 0.356 0.427 0.498 0.569 0.63

10 0.7

TRANSPORT COMPONENT: PARAMETERSIntroduction | Methods | Results | Conclusion

21

Distance to Nearest Inlet, DRelative Rank

Average Slope, SAAbsolute Rank

Rank Distance to Inlet

(feet)1 74.12 128.33 182.54 236.65 290.86 3457 404.88 470.49 553.1

10 727

TRANSPORT COMPONENT: PARAMETERSIntroduction | Methods | Results | Conclusion

22

Distance to Nearest Inlet, DRelative Rank

Average Slope, SAAbsolute Rank

Rank Average Slope

(degrees)1 62 123 174 215 276 317 358 399 42

10 >= 45

DEFINING NEAREST INLETIntroduction | Methods | Results | Conclusion

Conveyance Point Layer• Infrastructure nodes• Stream network points

23

PYTHON SCRIPTIntroduction | Methods | Results | Conclusion

Source Cell ElevationFrom DEM

Select Inlets whereRim < Cell Elevation

Run Near Analysis

24

http://pro.arcgis.com/en/pro-app/tool-reference/analysis/near.htm




Run Near Analysis

Compare Near_Dist To Flow Length

Set Near_Dist as Near_DistSet Rim Elev as Rim Elev

Flow Length > Near_Dist

25




Run Near Analysis



Flow Length > Near_Dist

26




Run Near Analysis



Set Near_Dist as Flow LengthSet Rim Elev as Elevation - dElevToOutlet

Flow Length < Near_DistFlow Length > Near_Dist

27




Run Near Analysis





28




Run Near Analysis




Average Slope = Elevation – Rim Elev / Near_Dist


29

EVALUATING FLOW PATH LENGTHSIntroduction | Methods | Results | Conclusion

30

Near Distance (ft) Measured Distance (ft)

360.45 388.95

EVALUATING FLOW PATH LENGTHSIntroduction | Methods | Results | Conclusion

31


360.45 388.95


229.08 374.89

EROSION POTENTIAL RISK MAPIntroduction | Methods | Results | Conclusion

32

Site Component

Transport Component

EROSION POTENTIAL RISK MAPIntroduction | Methods | Results | Conclusion

33

Site Component

Transport Component

EP FREQUENCY DISTRIBUTIONSIntroduction | Methods | Results | Conclusion

Median ScoreSite Component 30

Transport Component 8Erosion Potential 38

Erosion Potential

Transport Component Site Component

34

01,0002,0003,0004,0005,0006,000

27 51 79 110

142

173

214

270

410

618

Freq

uenc

y

Erosion Potential

0

5,000

10,000

15,00027 51 79 110

142

173

214

270

410

618

Freq

uenc

y

Erosion Potential

01,0002,0003,0004,0005,0006,000

27 51 79 110

142

173

214

270

410

618

Freq

uenc

y

Erosion Potential

INFLUENCE OF TRANSPORT COMPONENTIntroduction | Methods | Results | Conclusion

35

Areas of high imperviousness and low slope

In 14% of the cells, transport was > 50% of the EP.

Only 25% of the cells contribute <10%

Median contribution is 18%

ADAPTATIONS to EP EQUATIONIntroduction | Methods | Results | Conclusion

36

• Unbalanced influence between site [10,000] and transport [100] component

A B

• Equal weighting within components for each parameter • Is slope as or more important than the rest?• How much influence does land cover have?

C D E F G H

• Comparisons between neighboring watersheds• Absolute rankings for ALL parameters

CONCLUSIONSIntroduction | Methods | Results | Conclusion

37






GIS

Python

EP


38






GIS

Python

EP


39






GIS

Python

EP

FUTURE WORKIntroduction | Methods | Results | Conclusion

40

• Improvements to infrastructure corrected DEMs

• Incorporation of downstream land cover influence on transport erosion

41

QUESTIONS?

https://www.ofallon.org/sites/ofallonil/files/u71/stc_kids_stormwater-_color.pdf

Contact: [email protected]

urban erosion potential risk mapping with gis · 1. investigate the important parameters of soil...

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