Bank and Terrace Condition by Reach Figure 55a Figure 55b Figure 56a Figure 56b WILDCAT CREEK Total Percent Length of WILDCAT CREEK Total Percent Length of Percent Length of Bank Condition per Reach Different Bank Percent Length of Bank Condition per Reach Different Bank Conditions Upper Alluvial Plain Segment - 1998 Conditions for Entire Lower Canyon Segment - 1999 for Entire Lower Canyon (* Right and left banks and terraces combined) Upper Alluvial Plain (* Right and left banks and terraces combined) Segment Segment 100% 100% 100% 100% 5.0% 16% 90% 90% 90% 24% 90% 33% 80% 40% 80% 41% 80% 43% 80% 70% 70% 55% 54% 61% 59% 27% 58% 70% 61% 60% 70% 61% 60% 44% 62% 62% 50% 74% 74% 50% 60% 28% 60% 78% 24% 40% 40% Percent length Percent length 50% 30% 50% 30% 27% 25% 60% 20% 40% 40% 20% Percent length 32% 34% Percent length 20% 13% 21% 11% 10% 10% 30% 21% 57% 30% 0% 0% 46% 43% Entire length of Upper Entire length of Lower Canyon 20% 20% 39% Alluvial Plain Segment = 38% 37% Segment = 5.33 miles 33% 32% 2.55 miles 29% 28% 25% 25% 26% 26% 10% 10% 20% 22% 16% Stable Stable (threshold = 0.3' of (threshold = 0.3' of Eroding bank retreat) Eroding bank retreat) 0% 0% Revetted Trestle Rumrill Playfield 23rd Van Ness Church Vale San Pablo Hwy 880 Revetted Alvarado McBryde Dry Reach Perennial Rifle Range Kensington School Dam Reach Name of Reach Reach Road Reach to Jewel Name of Reach Lake mounts of eroding, revetted, and stable banks were measured ing bank than the Upper Alluvial Plain. The Lower Canyon has 2% and graphed for the Upper Alluvial Plain and Lower Canyon more stable banks than the Upper Alluvial Plain. If the areas that are A Segments. Bank erosion was measured wherever there was now revetted in the Plain were assumed to be eroding in the past, then evidence of at least 0.25 ft of bank retreat, as indicated by exposed roots, the relative amounts of stable and eroding bank are quite similar. The the freshness of bank sediments, shape of the bank in plan view, and small percentage of stable natural bank is indicative of incising chan- historical records. Note that even if the banks are shown as stable, the nels that are actively adjusting their hydraulic geometry. channel may be unstable if its bed is degrading or aggrading. The per- The reach based analysis shows that Church Reach has twice the cents reported represent the total for four banks: right and left banks percentage of eroding banks of any other reach on the Upper Alluvial above and below bankful. Continuous bank conditions are shown in the Plain and the least amount of stable natural bank. The erosion of its Appendix Streamline Graphs. In Figures 55a and 56a, the data are sum- banks may relate to the change in gradient from Vale Reach to Church marized for individual reaches within each of the two respective seg- Reach (Figure 88, page 69). In the Canyon, Kensington Reach has the ments. In graphs 55b and 56b, the percent length of bank erosion is to- greatest proportion of eroding banks. The abundance of landslides along (Photo 38) A revetted bank and a natural bank oppose each other along the taled for each segment. the banks in this reach might be a plausible explanation for its erosion. Alluvial Plain. Bed incision within the last 50 years is apparent along the base of the concrete and at the exposed roots on the right bank. About 35% more revetments exist in the Upper Alluvial Plain than McBryde Reach has the greatest percentage of stable banks (46%). in the Lower Canyon, whereas the Canyon has 33% more length of erod- 52 WILDCAT CREEK — A SCIENTIFIC STUDY Left and Right Bank Conditions by Segment Figure 57 Figure 58 WILDCAT CREEK WILDCAT CREEK Percent Length Right and Left Bank Conditions Percent Length Right and Left Bank Conditions Upper Alluvial Plain Segment - 1998 Lower Canyon Segment - 1999 100% 100% Bank Condition Bank Condition 90% 90% Stable Stable 80% 80% Eroding Eroding 70% (threshold = 0.3' 70% (threshold = 0.3' 64.6% of bank retreat) of bank retreat) 60% 58.1% Revetted 60% Revetted 50% 50% 41.8% 40.0% 39.1% 40% 38.0% 40% Percent length Percent length 34.1% 29.4% 30% 30% 24.1% 21.0% 20% 20% 10% 6.0% 10% 4.0% 0% 0% Left Bank (West) Right Bank (East) Left Bank (Southwest) Right Bank (Northeast) he percent lengths of eroding bank on the left side (south In the Lower Canyon, about (Photo 40) west) and right side (northeast) of the mainstem channel 6% more of the left bank (west side) Non- are plotted for the Upper Alluvial Plain and Lower Can- is eroding than the right bank (east engineered T revetment is yon Segments in Figures 57 and 58. For the Alluvial Plain Seg- side). This slightly greater amount failing into ment, the percent length of bank erosion is about 13% greater for of erosion on the west side could Wildcat Creek. the southwestern side than the northeastern side, even though there be due to the greater abundance of is a similar amount of revetment on both banks. We suggest that large complex earthflows on the the greater length of eroding bank on the south side results from steeper Berkeley Hills. channel migration southward across its alluvial fan. Perhaps the northern portion of the fan is being tectonically tilted toward the south. Alternatively, right-lateral creep along the Hayward Fault (Photo 39) The waning flood flow of January 1997 could be moving the fan northward, against the westward creek exposes an eroding left terrace bank near Vale flow, such that the south bank is eroding as it creeps into the creek. Road. SAN FRANCISCO ESTUARY INSTITUTE 2001 53 Types of Revetment by Reach Figure 59a Figure 59b Figure 60a Figure 60b WILDCAT CREEK WILDCAT CREEK Length of Different Length of Different Revetment Types per Reach Length of Different Length of Different Revetment Types per Reach Revetment Types and Upper Alluvial Plain Segment - 1998 Revetment Types and Lower Canyon Segment - 1999 Percent of Total Length Percent of Total Length of All Types for Entire 4,500 of All Types for Entire 4,750 Lower Canyon Segment 4,250 Other (wood, cyclone Sackcrete Upper Alluvial Plain 4,500 fence, debris, etc.) 274 Segment Other (wood, cyclone Rosgen Root Wad (In each white box, number on top is 4,000 Gabions Riprap 4,250 fence, debris, etc.) length of revetment (feet); number on 259 Revetment 4,000 Gabions bottom is the percent of total length) 3,750 Brick Concrete (In each white box, number on top is length of revetment (feet); number on Rosgen Vortex 3,500 3,750 838 Brick 211 82 Sheet Metal bottom is the percent of total length) 4% 1% 3,500 Rock Weir 3,250 Sheet Metal 121 3,250 3,000 670 Vandevere Vortex 1% 679 1117 514 3% 3,000 Sackcrete 2,750 3% Rock Weir 838 20% 769 2,750 15% 2,500 4% Riprap Vandevere Root 2,500 1512 2,250 Wad Revetment 513 1405 2,250 Concrete 2,000 7% 113 343 3746 2,000 1569 27% 1,750 487 1,750 28% 4981 1,500 12891 574 23% 1,500 59% 2579 600 Length of Revetment (feet) Length of Revetment (feet) 1,250 528 1,250 1114 61 118 1967 1,000 1% 2% 1897 1,000 113 750 446 750 2% 1203 1128 500 965 951 500 Total length of revetments = 639 Total length of revetments = 250 514 about 40% of Upper Alluvial 250 473 5% of Lower Canyon 0 Plain Segment which totals 0 Segment which totals 5.33 2.55 miles Alvarado McBryde Dry Reach Perennial Rifle Range Kensington School Dam Reach miles Trestle Rumrill Playfield 23rd Van Church Vale San Hwy 880 Reach Road Reach to Jewel Ness Pablo Lake Name of Reach Name of Reach igures 59a and 60a show the lengths of different types of revetment is concrete. From Figure 59a, we can see that nearly 3/4 revetment per reach along the Upper Alluvial Plain and the of a mile (3,740 ft) of the banks in San Pablo Reach are covered (Photo 41) Lower Canyon. Note the difference in vertical scale of the with concrete. Riprap is the second most common form of revet- A new wire basket F gabion and apron two graphs. Figures 59b and 60b show the total length and percent- ment, as shown in Figure 59b. Trestle reach is the only reach where revetment in age of each type of revetment per Segment. Concrete is the most riprap exceeds concrete. About 1,000 ft of riprap has been applied McBryde Reach, January 1998. common material used in Wildcat for bank revetment. Box culvert to the banks near the railroad trestle (photo 29, page 46). Much of it structures, poured concrete retaining walls, barriers that consisted is undersized and has been transported by high flows. of stacked fragments of broken concrete, and mortared banks are In the Lower Canyon, only 5% of the total length of the banks some of the ways that concrete is used to revet the banks of Wildcat is revetted (Figure 56a, page 52). Riprap exceeds the amount of con- Creek. In many cases these revetments have accelerated erosion at crete by 8% (Figure 60b) in the Canyon. About 69% of this revet- their downstream ends or on opposite banks. ment is located in Alvarado Park (Figure 60a), where much was Based upon Figure 55b on page 52,we know that 40% of the put in after a restoration project was conducted to remove two small banks are revetted.