HYDRAULIC GEOMETRY OF STREAMS & INTRODUCTION OF ELEVATION AS THE NEW STREAM CLASSIFYING PARAMETER

1. HYDRAULIC GEOMETRY OF STREAMS & INTRODUCTION OF ELEVATION AS THE NEW STREAM CLASSIFYING PARAMETER RAJAN JHA, EIT, VIRGINIA TECH ADVISOR : Dr PANOS DIPLAS

2. Outline • Hydraulic Geometry of streams - An Overview • Stream classification system- An Overview • Compilation of hydraulic geometric field data- UK, US & Canada streams • Grain size (D50) based statistical analysis of the field data • Elevation based statistical analysis of the field data • Overall conclusion of this study

3. Hydraulic geometry of streams – An overview • Hydraulic geometric equations describe the quantitative variations of stream properties with changing discharge. [Ferguson, 1986] • Leopold and Maddock (1953) established following hydraulic geometric relations in power form: w = aQ.5 d = cQ.33 v = kQ.17 • Hydraulic geometric variables considered in this study : Aspect ratio, channel slope & Sinuosity (All dimensionless)

4. Defining the hydraulic geometric terms • Aspect Ratio (Ar)– For any channel or stream, it is defined as the ratio of bankfull width to bankfull depth

5. Defining the hydraulic geometric terms • Channel gradient (Sc) – For any channel or stream, it is defined as the ratio of drop in the elevation per unit horizontal length

6. Defining the hydraulic geometric terms • Sinuosity (P) – For any stream reach, it is defined as the ratio of actual sinuous length (channel length) to the shortest straight line distance (valley length).

7. Compilation of hydraulic geometric field data

8. Stream classification system –An overview • More than 20 different stream classification systems have been proposed till date • Streams have been classified on the basis of bed material, patterns, age, sediment inputs, orders etc • Rosgen (1994, 1996) developed a new approach to channel classification system where he divided the channels into four hierarchical levels • Even with the existence of so many available classification systems, none of them have been accepted universally till date

9. Research Objectives • Calculating most probable values of Ar, Sc & P occurring together in nature for each stream type : sandy, gravel and cobble • Introducing “elevation above mean sea level” as the new parameter for stream classification system • Identifying trends existing in the behavior of stream variables (Ar, Sc & P) while moving upstream

10. Median grain size (D50) based analysis of hydraulic geometry of streams Brief Outline: • Dividing field data into sandy, gravel & cobble groups • Application of joint probability distribution on Ar, Sc, P of each group • Finding MPVs of the hydraulic variables for each group occurring together • Analyzing 3-Dimensional plots

11. D50 based distribution of cumulative data

12. Sandy, Gravel & Cobble streams Sandy streams Cobble streams

13. Modal values of Ar, Sc & P for each stream type • Probability density functions of hydraulic geometric variables were estimated for each stream type and modal values were calculated

14. Joint probability distribution of Ar, Sc & P • Using kernel density estimation and smoothing on a fine grid in statistical software R, joint probability plots in 3 dimensional forms were also obtained for each stream type • The peak in the plots represent the most probable values (MPVs) of the three variables [Ar, Sc, P] occurring together in the nature for each stream type

15. Joint probability 3-D plots for sandy streams

16. Joint probability 3-D plots for gravel streams

17. Joint probability 3-D plots for cobble streams

18. Most probable values of Ar, Sc & P occurring together

19. Elevation based analysis of hydraulic geometry and establishing it as the new stream classifying parameter Brief Outline: • Dividing complete field data into 14 fine elevation ranges • Calculation of Modal values of Ar, Sc & P for each range • Formation of final fine elevation zones and calculating MPVs for each zone • Classifying sandy, gravel and cobble streams on the basis of the 5 elevation zones

20. Grouping of data into 14 fine elevation zones

21. Modal values calculated for 14 elevation ranges

22. Formation of final 5 elevation zones

23. MPVs calculated for each of the 5 zones

24. 3 Dimensional Probability density plots • Presented for highest elevation zone : 5000 ft & above • Rest all zones followed similar distribution behavior

25. Elevation based classification of sandy, gravel and cobble streams

26. Summary & Conclusion • Statistical analysis is a strong tool in understanding the co-relation and interdependency existing amongst the stream variables • Elevation provides a consistent framework for grouping streams on the basis of its hydraulic characteristics. Thus elevation based classification can be considered as the new morphology based stream classification system.

27. Summary & Conclusion • Elevation based classification provides a logical progressive expression of trends occurring in channel characteristics . • MPVs can be very useful for engineers while designing canals, channels and obtaining representative dimensions for laboratory and numerical modeling

28. Acknowledgement • Dr Panayiotis Diplas- Professor & Department Chair, Civil & Environmental Engineering, Lehigh University , (Previously at Virginia Tech) • Dr Shrey K. Shahi- Stanford University • NCHRP – National Cooperative Highway Research Program (Funding Agency)

29. Dedicated • Dedicated to those who lost their lives in the tragic incident called “Himalayan Tsunami”, June 2013, India. • More than 5700 people died and many still missing

35. Questions

36. Thank you