Fluvial Driven Alluvial Fans

Transcription

1 Fluvial Driven Alluvial Fans Restoration Project Evaluations - Examples from the Russian and Napa River Watersheds Mia Docto Masters Thesis UC Berkeley

2 1. Basic Fan Description 2. Fluvial Driven Fan Characteristics 3. Restoration Project Evaluations 4. Key Lessons Learned presentation outline

3 Alluvial fans are gently sloping, fan-shaped landforms created over time by deposition of eroded sediment fan description 1

4 Debris Flow alluvial fans alluvial fans 2

5 Death Valley Fan alluvial fans 3

6 Fluvial Driven alluvial fans alluvial fans 4

7 Erosion Sediment Transport Deposition 1.) Stream flow carriers sediment through canyon. 2.)Stream leaves canyon dispersing water and sediment. 3.) Area below canyon forms a cone of deposited material. fan formation 5

8 zone of deposition zone of transportation zone of erosion fan formation 6

9 Alluvial Fan Creeks & Channels 7

10 fan channel fan channels are different from river valley channels river valley channel fan characteristics 8

11 Alluvial Fan Typical River fan characteristics 9

12 distributary channels: disperse water away from main channel sheet flow: thin sheet of water flowing over surface of fan fan characteristics 10

13 rock transport - powerful streamflow flow waters move boulders, cobble and gravel along fan channel rock deposition rocks are deposited at various points on the fan fan characteristics 11

14 In high flows mainstem river would cut into fan deposits. Alluvial fan deposits are an important source of coarse sediment. fan characteristics 12

15 unconsolidated material - drains easily Loosing stream dry channel Bedrock gaining stream fan characteristics 13

16 alluvial fan channels have seasonal flows fan characteristics 14

17 Fan apex Channelized zone Braided zone Sheet flow zone fan characteristics 15

18 (Parson s Creek, Sonoma County) fan characteristics 16

19 1942 Braided Channel Wetland Oak Savanna Distributary Channels fan characteristics 17

20 Alluvial Fans are unique types of creeks 18

21 Selby Creek Watershed Parsons Creek Watershed Morrison Creek Watershed Ritchie Creek Watershed Sulfur Creek Watershed Redwood Creek (Upper) Watershed case study sites 19

22 In the Napa Valley alluvial fans line the valley floor. In some locations fans merged together at the toe creating a bajada. The largest fans are located on the western side Miles lidar analysis 20

23 Fans push river across valley lidar analysis 21

24 Relic channel at fan head Channels at fan toe Miles Miles lidar analysis 22

25 relic channels current channel lidar analysis 23

26 current channel Fan Head relic channel Mid Fan Fan Toe lidar analysis 24

27 current channel distributary channels lidar analysis 25

28 scars from flooding scars from flooding distributary channel oblique aerial 26

29 Understanding Alluvial Fan Channel Restoration and Management 27

30 selby creek 28

31 1940 Distributary Channels No Continuous Riparian Corridor Remnants of Oak Savanna Distributary Channels (photograph from SFEI) historic aerial photograph 29

32 SELBY CREEK CONCEPTUAL MODEL (As described in project documents) IDENTIFIED PROBLEM SITE CONSTRAINTS OVERALL PROJECT OBJECTIVES RESTORATION ACTIONS OBJECTIVES Culvert blocks fish passage through creek Channel lack riparian vegetation Poor instream habitat conditions Unstable banks Legacy trees undercut project limited to current width of channel Create series of pools for fish passage and habitat Increased riparian vegetation and associated reduction in sediment input. Decreased water temperatures. Increase bank stability. Create a low flow meandering channel. opposing deflectors log boulder wing deflectors cross channel v-weir boulder wing deflectors boulder stream bank protection armored banks hand rocked trees reconnected stream to floodplain removal of mid channel willows live willow mattresses live willow baffles enhance low flow channel to develop meanders increase resting areas, pools, and large woody debris stabilize eroding banks reduce sediment inputs to main stem river rehabilitation of instream habitat limit channel incision decrease water temperatures protect existing trees increase native vegetation live willow brushes riparian vegetation enhancement remove invasive vegetation increase riparian canopy selby creek conceptual model 30

33 UNDISTURBED ALLUVIAL FAN SYSTEM high erosion in mountainous areas PROJECT SPECIFIC OBJECTIVES NEW TYPE OF ALTERED SYSTEM stream flows at high velocities carrying sediment through canyon stream exits canyon change in slope causes stream to deposits sediment channel migrates back and forth over thousands of years forming a fan shape of deposited rocks channel form is braided with distributary channels or entrenched fan head channel enhance low flow channel to develop meanders increase resting areas, pools, and large woody debris stabilize eroding banks reduce sediment inputs to main stem river rehabilitation of instream habitat limit channel incision decrease water temperatures protect existing trees Single channel, with stabilized banks, pool habitat, and vegetated with willow trees fan vegetated with oak savanna andromous fish use channels to seasonally migrate to spawning habitat in headwaters increase native vegetation remove invasive vegetation increase riparian canopy conceptual model comparison 31

34 Quantity Techniques and Structures 18 Boulder streambank protection sites - totally V-weirs 102 Boulder wing deflectors (including opposing boulder wing deflectors) 4 Log/boulder wing deflectors 145 Live woven willow wall 50 Live willow brush mattress 281 Live willow brush mattress 26 Live willow siltation baffles, totalling Live willow brushes, totalling Live willow cluster sites, totalling 552 sq ft. 3 Boulder armor sites, totalling 35 yards 96 Gabion basket repaired (NRCS site) 6 Boulder wing deflectors repaired (NRCS site) 2 Undercut pines, hand rocked 23,956 ft Grading Misc. Removal of mid-channel willows causing disturbance selby creek 32

35 Digger Log To create pool habitat ground photograph comparisons 33

36 Opposing Boulder Wing Deflectors To create pool habitat & improve fish passage ground photograph comparisons 34

37 Rip Rap To stabilize bank ground photograph comparisons 35

38 Willow Baffles To increase native vegetation ground photograph comparisons 36

39 Benefit/ Goals Improved in-stream habitat - including pools, resting areas, shelter and large wood. Increased riparian vegetation and associated reduction in sediment input. Decreased water temperatures. Increased bank stability Improved fish passage Success Evaluation Low success Low success, majority of willow plants died No data - undetermined Success varies No data, culvert still fish barrier selby creek 37

40 project 2 project 1 redwood creek 38

41 1942 Braided Channel Wetland Oak Savanna Distributary Channels historic aerial photograph 39

42 Braided Channel No Continuous Riparian Corridor 1942 Gravel Bar historic aerial photograph 40

43 REDWOOD CREEK PROJECT 1 CONCEPTUAL MODEL (As described in project documents) IDENTIFIED PROBLEM SITE CONSTRAINTS OVERALL PROJECT OBJECTIVE RESTORATION ACTIONS OBJECTIVES Need for project not stated in project documents. 0.4 miles of channel available for restoration project Enhance 1,500 feet section of Redwood Creek for salmonid species. Create habitat for rearing juveniles. Enhance stream for Coho migration boulder deflectors upstream facing boulder weirs mid-stream boulder cluster with large woody debris pool enhancement boulder deflectors with willows erosion control vegetative plantings sediment recruitment willow cluster plantings cover redwood creek 1 conceptual model 41

44 UNDISTURBED ALLUVIAL FAN SYSTEM high erosion in mountainous areas PROJECT SPECIFIC OBJECTIVES NEW TYPE OF ALTERED SYSTEM stream flows at high velocities carrying sediment through canyon stream exits canyon pool enhancement change in slope causes stream to deposits sediment channel migrates back and forth over thousands of years forming a fan shape of deposited rocks channel form is braided with distributary channels or entrenched fan head channel erosion control sediment recruitment cover Single channel, with stabilized banks, pool habitat, and vegetated with willow trees fan vegetated with oak savanna andromous fish use channels seasonally to migrate to spawning habitat in headwaters conceptual model comparison 42

45 3 7 9 A REDWOOD CREEK Knights Valley, Sonoma County, California field survey construction zone END OF SURVEY N W wp 2 A Cabled boulders on RB, but instream boulders covered in cobble Plan called for weir, j-hook installed. 3 CABLED J HOOK cabled CONSTRUCTED LEVEE 5 5a 5b 5c B Three pairs of boulder deflectors found. Pools formed along LB 5b and 5c. Three more boulder clusters found on RB, about 285 upstream. No cables, unclear if part of project According to as-built map, three deflectors on RB and four on LB. 5 BOULDER DEFLECTORS ACCESS ROAD 5d N W e 5f F 5 wp 7a Six cabled clusters, mid-channel along 258 feet of channel. Pool excavated. 7 INSTREAM BOULDER STRUCTURES 7b No cabled boulders found mid-channel. Found three boulder clusters/deflectors on LB. Pools formed at two upstream clusters. 7c C 7 LEVEE 10a LEVEE 9 B 9a cabled 10b 9 C 10c Four stuctures found on RB. Unclear if these were deflectors or weirs Five structures in plan, four installed along 113 feet of channel. Treatment placed on BFC (bankfull channel?). No photos. 10 BOULDER DEFLECTORS N W D 10 9 D cabled 10d 11 ACCESS ROAD wp START OF SURVEY (fence) flow C 11 11c 2 CABLED J HOOK No vestige found. Location approximated Plan called for weir, j-hook installed. 6 RIP RAP No vestige found Installed 40 feet of riprap along left bank, parallel to stream. From 2005 report: Riprap not called for in plan. Appears that excess material used for riprap would have been more appropriately used to create another deflector. 9 WEIRS One weir (9A) remains intact. Unclear if other boulder structures along RB were part of Feature 9: instream Weirs or Feature 10: Boulder Deflectors Series of four weirs along 414 feet of channel. From 2005 report: All weirs exceed 1 height called for in plan. 11 BOULDER DEFLECTORS Six structures found Series of six boulder deflectors along 150 feet of LB. From 2005 report: No boulder deflectors called for at this site in the plan. Extra work poorly implemented, need to be restacked for correct functioning. N waypoints based on NAD27 surveyed project features 100 ft wp X estimated location of as-built feature Base aerial from Google Earth, image dated 10/24/2009 redwood creek 1 project map 43

46 J-Hook To create pool habitat ground photograph comparisons 44

47 J-Hook To create pool habitat ground photograph comparisons 45

48 Rock Weir To create pool habitat ground photograph comparisons 46

49 Of the 30 installed rock structures only 11 could be considered functioning. ground photograph comparisons 47

50 project 2 Instream ford removal project 1 redwood creek - project 2 48

51 REDWOOD CREEK PROJECT 2 CONCEPTUAL MODEL (As described in project documents) IDENTIFIED PROBLEM SITE CONSTRAINTS OVERALL PROJECT OBJECTIVE RESTORATION ACTIONS OBJECTIVES Ford (instream road crossing) blocks fish passage through creek 0.6 miles of channel available for restoration project Remove ford across Redwood Creek Rehabilitate channel to allow fish access upper watershed ford removed rock ramps separated by pools remove ford and rehabilitate the channel to allow fish access to upstream areas design for fish passage by swimming rather than leaping armored bank rock ribs prevent thalweg from moving from right to left bank rock barb live willow mattresses make fanhead trench self-maintaining so that sediment is carried through reach rather than deposited rock and willow lifts create riparian cover and protect against bank erosion oak trees planted revegetation of fan redwood creek 2 conceptual model 49

52 UNDISTURBED ALLUVIAL FAN SYSTEM high erosion in mountainous areas PROJECT SPECIFIC OBJECTIVES NEW TYPE OF ALTERED SYSTEM stream flows at high velocities carrying sediment through canyon stream exits canyon change in slope causes stream to deposits sediment channel migrates back and forth over thousands of years forming a fan shape of deposited rocks channel form is braided with distributary channels or entrenched fan head channel fan vegetated with oak savanna design for fish passage by swimming rather than leaping prevent thalweg from moving from right to left bank make fanhead trench self-maintaining so that sediment is carried through reach rather than deposited create riparian cover and protect against bank erosion revegetation of fan Single channel, with stabilized banks, pool habitat, and vegetated with willow trees andromous fish use channels seasonally to migrate to spawning habitat in headwaters remove ford and rehabilitate the channel to allow fish access to upstream areas conceptual model comparison 50

53 Irrigation pipe Step Pools J-hook Rip Rap Boulder Cluster ² 50 ft Rock and willow lifts Boulder Cluster Rip Rap redwood creek 2 project map 51

54 rock structures breaking apart live willow mattress eroding & pools filling in redwood creek - project 2 52

55 XS XS Axis Title Oct. 28, 2011 Apr. 20, 2012 Axis Title Oct. 28, Jun- 12 Feb. 15, Feb. 15, Axis Title Axis Title Channel has aggraded 2-3 feet in 2 years XS- 4 Control cross section XS Axis Title Oct. 28, Jun- 12 Feb. 15, 2013 Axis Title Oct. 28, 2011 Apr. 20, Feb. 16, Axis Title Axis Title redwood creek - project 2 53

56 pools filling in with rock redwood creek - project 2 54

57 live willow mattresses falling apart redwood creek - project 2 55

58 rip rap channel banks falling apart redwood creek - project 2 56

59 boulder cluster - instream structure destroyed redwood creek - project 2 57

60 The feasibility of small scale highly engineered habitat enhancement projects should be reconsidered given the dynamic nature of the system. Large scale management is needed. Site sediment deposition and transport capacity should be assessed to ensure appropriate models and methods are used in the site design. Stream flow and infiltration rates need to be studied to determine the duration of pools in channel. Fish surveys and studies need to be conducted to determine how fish use these channels for migration. key lessons learned 58

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