1. Hydrology: Discharge, Hydrographs, Floods, and Sediment Transport Unit 1: Module 4, Lecture 2

2. Developed by: Merrick, Richards Updated: August 2003 U1-m4-s2 Objectives  Students will be able to:  interpret hydrographs.  explain the effects of urbanization on storm hydrographs.  describe factors that influence overland flow of water.  describe patterns of deposition based on particle size in a stream bed.  explain how sediment load is related to discharge.

3. Developed by: Merrick, Richards Updated: August 2003 U1-m4-s3 Hydrology  Exhibits wide variation across watersheds  Related to  Precipitation  Geology (including topography)  Landuse & land cover  Hydrology is one of the primary factors influencing the physical and biological characteristics of streams

4. Developed by: Merrick, Richards Updated: August 2003 U1-m4-s4  Q - Volume of water passing a point per unit time.  Q=VA or WDV modified from www.usda.gov/stream_restoration/chap1.html Figure 1.18 Discharge

5. Developed by: Merrick, Richards Updated: August 2003 U1-m4-s5 www.aquatic.uoguelph.ca/rivers/chphys.htm Discharge and hydrographs

6. Developed by: Merrick, Richards Updated: August 2003 U1-m4-s6 Annual hydrographs

7. Developed by: Merrick, Richards Updated: August 2003 U1-m4-s7 www.usda.gov/stream_restoration/chap1.htmlFigure 1.14 Storm hydrograph

8. Developed by: Merrick, Richards Updated: August 2003 U1-m4-s8 http://www.usda.gov/stream_restoration/Images/scrhimage/chap1/fig1-15.jpg Figure 1.15 Effects of urbanization on a storm hydrograph

9. Developed by: Merrick, Richards Updated: August 2003 U1-m4-s9 Flow paths www.usda.gov/stream_restoration/chap1.html Fig. - 2.10

10. Developed by: Merrick, Richards Updated: August 2003 U1-m4-s10 Overland flow  Occurs when soils are  saturated (after snow melt or heavy rain)  have low permeability (e.g., clay)  Strongly influenced by landform and land use  Coarse textured glacial deposits are highly permeable; bedrock & ancient lake bottoms are impermeable or have low permeability  Impervious surfaces (parking lots, structures) create impervious surfaces;  Forest harvest practices and agricultural practices affect stream flow

11. Developed by: Merrick, Richards Updated: August 2003 U1-m4-s11 www.mmsd.com/stormwaterweb/Volume1B.htm Overland flow and development

12. Developed by: Merrick, Richards Updated: August 2003 U1-m4-s12 www.aquatic.uoguelph.ca/rivers/chphys.htm Flooding  We tend to have a biased view of floods as unpredictable, disastrous events, while in reality they are predictable and necessary occurrences.  How does impervious surface affect the likelihood of flooding?

13. Developed by: Merrick, Richards Updated: August 2003 U1-m4-s13 Flood probabilities  Recurrence interval  “1 in 100 year flood”  = probability of 0.01 or 1%  Also referred to as the recurrence interval  Defined as P = 1 / T, where:  P = Flood probability  T = Recurrence interval

14. Developed by: Merrick, Richards Updated: August 2003 U1-m4-s14  Rapid runoff into channelized streams increase flood frequency and enhance downstream peaks in flood hydrographs. www.aquatic.uoguelph.ca/rivers/chphys.htm Human influence on floods

15. Developed by: Merrick, Richards Updated: August 2003 U1-m4-s15 Sediment transport

16. Developed by: Merrick, Richards Updated: August 2003 U1-m4-s16 Sediment transport earthsci.org/teacher/basicgeol/stream/stream.html#Erosion%20by%20Streams Current Direction Bed load particles moving by saltation Stream Bed

17. Developed by: Merrick, Richards Updated: August 2003 U1-m4-s17 CategoryDia (mm)Wentworth scale Boulder Cobble > 256< -8 Large Small 128 - 256 64 - 128 -7 -6 PebbleLarge Small 32 - 64 16 - 32 -5 -4 GravelCoarse Medium Small 8 - 16 4 - 8 2 - 4 -3 -2 SandVery Coarse Coarse Medium Fine Very Fine 1 - 2 0.5 - 1 0.25 - 0.5 0.125 - 0.25 0.063 - 0.125 0123401234 Silt< 0.063> 5 The transportation of materials

18. Developed by: Merrick, Richards Updated: August 2003 U1-m4-s18 Erosion Forms and directions of erosion by running water. H = headward erosion V = vertical erosion L = lateral erosion www.aquatic.uoguelph.ca/rivers/chphys.htm

19. Developed by: Merrick, Richards Updated: August 2003 U1-m4-s19 Erosion in action Fig. - 7.23 Fig. - 7.28

20. Developed by: Merrick, Richards Updated: August 2003 U1-m4-s20  Deposition resulting in multiple channels  Deposition within a single channel aquatic.uoguelph.ca/rivers/chphys.htm Deposition aquatic.uoguelph.ca/rivers/chphys.htm

21. Developed by: Merrick, Richards Updated: August 2003 U1-m4-s21 www.usd.edu/esci/figures/158401.JPG Sediment deposition and current velocity

22. Developed by: Merrick, Richards Updated: August 2003 U1-m4-s22 Sediment load increases with discharge www.usda.gov/stream_restoration/chap1.html Fig. - 8.58

23. Developed by: Merrick, Richards Updated: August 2003 U1-m4-s23 Variation in sediment transport

24. Developed by: Merrick, Richards Updated: August 2003 U1-m4-s24  2001 Minnesota River at St. Peter, MN daily average flow and tss samples (draft) State of the Minnesota River: Summary of Results 2000 and 2001 (Mn River Basin Data Center) Landuse/seasonal affects on sediment delivery to the Minnesota River

25. Developed by: Merrick, Richards Updated: August 2003 U1-m4-s25 Longitudinal profile of a river  As discharge increases:  Channel Width increases  Channel Depth increases  Mean velocity is stable  Bed Material size decreases  Slope decreases  Sediment storage increases www.usda.gov/stream_restoration/chap1.html Fig. - 1.28r