Sedimentation from Unpaved Roads in the San-Geronimo sub-Watershed.

gayoldMécanique

21 févr. 2014 (il y a 3 années et 8 mois)

68 vue(s)








Sedimentation from Unpaved Roads in the San-Geronimo sub-Watershed.

(Spring/Summer 2002)











Reuven Walder - Watershed Biologist





SALMON PROTECTION AND WATERSHED NETWORK

P o s t O f f i c e B o x 4 0 0 • F o r e s t K n o l l s, C A 9 4 9 3 3
P h o n e: 4 1 5 - 4 8 8 - 0 3 7 0 • F a x: 4 1 5 - 4 8 8 - 0 3 7 2
s p a w n @ s p a w n u s a.o r g • www.s p a w n u s a.o r g
Summary


Crews surveyed a total of 11,241 feet (2.13 miles) of dirt and gravel 'Non Maintained County
Road' and private road and 22 stream crossings in the San Geronimo sub-Watershed between
March and June 2002. Based on these surveys, an estimated 21,097 Yds
3
of sediment have been
delivered to the creek from these roads while calculations estimate that 758 Yds
3
will be
delivered to the creek system in the next 10 years. Of the 22 stream crossings, 11 are in need of
repair. Failure of all 22 crossings would result in an estimated additional 6539 Yds
3
delivered to
the creek system. Since the Regional Water Quality Control Board has officially listed this
watershed as 'impaired' for pathogens, nutrients and sediment, it is critical to address these roads
and prevent further unnecessary degradation to habitat of threatened salmonid populations.
Before this process commences we recommend completion of the ~50% of roads still in need of
survey. Local agencies have engaged in a process to address sedimentation from their roads.
Yet these 'Non Maintained County Roads' and private roads are not included in this process. We
recommend that a collaborative process between gove rnment agencies now gaining expertise in
road maintenance and repair to reduce sedimentation, SPAWN and any other local community
organizations interested in this problem, begin to work with local landowners to begin a process
to remove this source of sedimentation.







2
Introduction:

Soil erosion and sedimentation are recognized as si gnificant contributing factors to the decline of
salmonids in the Lagunitas Creek Watershed, and unpaved roads are a major contributor to the
problem.

A grant from the National Fish and Wildlif e Foundation provided funding to conduct a
preliminary assessment of approximately half of the unpaved roads (> 2miles) suspected to be
contributing excessive amounts of sediment to the stream system.

Sites were ranked for priority of repair based on the total sediment delivery (in Cubic Yards).
These data provide the preliminary framework for addressing sedimentation issues.


Methods:

Based on professional judgement and discussi ons with long-time residents, unpaved, non-
maintained county roads and private roads consider ed to be in poor condition were surveyed by
walking the road length noting all gulli es, rills and roadside drainages.

The following parameters were collected at each site:
1) Road Length and Width

2) Road composition dirt, gravel, dirt w/gravel, gravel w/dirt etc.) and presence of water
bars.

3) Location

4) Slope (Insloped, Outsloped, Neither); Incline (Flat, Slight, Moderate, Steep)

5) Estimated past Sediment Delivery - The volume (yds
3
) of past sediment delivery of soil
contributed by gullies, rills, roadside drainages and surfaces was calculated by measuring the
length, width and height of each feature.

6) Estimated future Sediment Delivery - The volume (yds
3
) of soil contributed by gullies, rills,
roadside drainages and road surface was calculated using the following formula in the California
Salmonid Stream Habitat Restoration Manual - Upslope Assessment and Restoration Practices:

Q
S
= (A*E)/27 * T*D

Where Q
S
= sediment delivery (yds
3
) from surface erosion
A = exposed area (l x w of eroded area in ft
2
),
E = erosion or lowering rate (ft/yr), - see below
T = time (years, usually 10 to 30 yrs - 10 yrs for these calculations)
D = delivery ratio (% of erosion that is delivered to the stream)

"E" was calculated as the erosion rate based on the following recommended categories in
the Salmonid Restoration Manual which account fo r different rates of erodibility depending
on the composition of the road bed material.
3

Cutbanks and continually bare soil areas (Low, Moderate, High).0.01, 0.03, 0.05
Native surfaced (unimproved, dirt) roads 0.03
Rock surfaced roads ....0.02

7) Stream Crossings condition and relevent data were recorded and included, Type (CMP, SSP,
Plastic, Cement), Length, Diameter, Inlet and Outlet Status (open, plugged, compressed
or crushed) and Potential Blow Volume (calculated as the volume, L x W x H of
sediment around crossing, that would be delivered to the creek system if the crossing
were to fail).

Sites were sorted and ranked for priority of repair based on the total sediment delivery (Q
S
) from
rills, gulies, drainages and road surfaces. Sediment delivery from stream crossings were not
included in the ranking but are listed in Appendix I.


Results:

A total of 11,241 feet (2.13 miles) of dirt and gravel road were surveyed in Woodacre, Forest
Knolls and Lagunitas between March and June 2002 (Figure 1-5). Based on these surveys, an
estimated 21,097 Yds
3
of sediment have been delivered to the creek (Table 1). Each site was
sorted based on the amount of future sediment delivery (Q
S
) and is listed in based on their
priority (Table 1). Without repair of these road surfaces we estimate the total sediment delivery
(total Q
S
) will be 758 Yds
3
(Table 1) in the next 10 years.

A total of 22 stream crossings were inventoried on these roads. Eleven of these crossings were
either partially or totally plugged or compressed. Failure of these 11 crossings would result in an
additional estimated 3042 Yds
3
of sediment delivered to the creek system. Failure of all 22
crossings, would result in 6539 Yds
3
of sediment delivered to the creek system. See Appendix I
for a listing of the data at each site.


Discussion:

The Regional Water Quality Control Board has officially listed the Lagunitas Watershed as
'impaired' for pathogens, nutrients and sediment and it is no surprise that unpaved roads
contribute significantly to sediment input into stream systems in this hilly region. Local
government agencies including Marin County Open Space, Marin Municipal Water District and
State and National Park Services located in the watershed have begun to assess the impact of
roads on their land and and have entered into a memorandum of understanding, which has begun
a process to reduce sedimentation from these sources (Todd Steiner, member, Lagunitas Creek
Sediment and Riparian Management Technical Advisory Committee - TAC, pers. comm.).

Unfortunately, these positive agency activities ar e not addressing the considerable amount of
roads on private lands or are classified as 'Non Maintained County Roads'. Our findings
demonstrate that many of these roads are in need of major repair and have and continue to
contribute significant sediment loads to local streams. All of these roads should be repaired to
minimize sedimentation and other impacts to salmoni d populations. Before that process begins,
we recommend a completion of the ~50% of roads that still needed to be surveyed and combined
4
with the information presented here to determine a prioritization schedule for repair. Lastly we
recommend that a collaborative process between gove rnment agencies now gaining expertise in
road maintenance and repair to reduce sedimentation, SPAWN and any other local community
organizations interested in this problem, begin to work with local landowners to begin a process
to remove this source of sedimentation. Such a process is likely to have additional benefits for
salmonids beyond reducing sediment load from roads by educating local landowners about
sedimentation of streams as related to landowner practices.


Literature Cited

Upslope Assessment and Restoration Practices, Ca lifornia Salmonid Stream Habitat Restoration
Manual. Chapter 9. 97 pp., Califor nia Department of Fish and Game.


Acknowledgements:

The success of this project is based on the following committed volunteers who participated in
the effort, David Ford, Christine Keyser, Yoav Potash, Todd Steiner and Dick Webster. Rich
Koehler, Geologist for William Lettis and Associ ates in San Rafael, provided valuable support
and guidance in this project. We acknowledge the financial support of the Bella Vista
Foundation, National Fish and Wildlife Foundation and the dedicated members of SPAWN.























Table 1. Rank of roads losing the greatest amount of sediment in total cubic yards.












Past
Sediment
Delivery in
Total CuYds
Past
Sediment
Delivery in
Total
Future
Sediment
Delivery
in Total



Rank based
5
Site # Village Road CuYds/Ft
CuYds (
Q
S
)
on (
Q
S
)

20 Forest Knolls Aztec Rd. 2107 1 102 1
17 Lagunitas La Vuelta Rd. 77 0.19 85 2
15 Lagunitas Rodeo Ave. 1529 1 70 3
13 Lagunitas East Cintura Ave. 553 0.53 66 4
12 Woodacre Hill Rd. 2362 2 63 5
5 Woodacre Conifer Rd. 3307 5 47 6
16 Lagunitas Rodeo Ave. 326 0.40 45 7
19 Lagunitas Potrero Rd. 6062 3 42 8
18 Lagunitas East Cintura Ave. 134 0.28 35 9
9 Woodacre Upper Carson Rd. 407 1 35 10
1 Woodacre Park Rd. 1820 5 29 11
14 Lagunitas Rodeo Ave. 253 1 24 12
6 Woodacre Sylvan Rd. 1034 2 24 13
7 Woodacre Salix Rd. 359 0.97 24 14
8 Woodacre Upper Carson Rd. 351 0.50 21 15
10 Woodacre Conifer Rd. 63 0.31 16 16
3 Woodacre Conifer Rd. 0 0 13 17
2 Woodacre Conifer Rd. 353 2 11 18
11 Woodacre Conifer Rd. 0 0 6 19
4 Woodacre Conifer Rd. 20

Grand Total 21097 26 758







6

Figure 1. Map of San Geronimo Creek and its tributaries.
7





Figure 2. Road sediment delivery survey sites 1-6 and 8-11.


8





Figure 3. Road sediment delivery survey sites 7 and 12.


9





Figure 4. Road sediment delivery survey sites 13-19.



10




Figure 5. Road sediment delivery survey site 20.


11Appendix I
Road Name: Park Rd. Village: Woodacre Site Number: 1
Location: From intersection of Park and Redwood uphill 484 feet.
Road Composition: Dirt (w/some pavement) Water Bars?: None
Length: 484 Width: 10
Slope
(Insloped, Outsloped, Neither):
Neither

Incline
(Flat,Slight,Moderate,Steep):
Slight


Estimated Past Erosion:
Total Erosion
Total Yds
3 Yds
3/Foot
1820.25 5.17


Estimated Future Erosion:
Area Erosion Rate Delivery Percentage Sediment Delivery
(A) (E) (D) in Yds
3 (Q
s)
193.40 0.02 1.00
29.40

Rank Priority Based on Future Erosion (Q
s): 11


Stream Crossings:
Crossing
#
Type: Length: Diameter: Inlet Open?
(OCPR):
Outlet Open?
(OCPR):
Estimated Fill
Prism (Blowout)
in Yds
3
:
SX1A-1 cement 20 10" O O 71.99

12
Road Name: Conifer Rd. Village: Woodacre Site Number: 2
Location: From intersection of Park and Conifer uphill to the right 100 feet
Road Composition: Dirt w/some Bedrock Water Bars?: None
Length: 100 Width: 10
Slope
(Insloped, Outsloped, Neither):
Mostly Outsloped

Incline
(Flat,Slight,Moderate,Steep):
Steep


Estimated Past Erosion:
Total Erosion
Total Yds
3 Yds
3/Foot
352.50 1.76


Estimated Future Erosion:
Area Erosion Rate Delivery Percentage Sediment Delivery
(A) (E) (D) in Yds
3 (Q
s)
75.00 0.03 1.00
11.11

Rank Priority Based on Future Erosion (Q
s): 18


13
Road Name: Conifer Rd. Village: Woodacre Site Number: 3
Location: Adjacent to site 2 uphill 134 feet
Road Composition: Dirt w/Gravel Water Bars?: None
Length: 134 Width: 10
Slope
(Insloped, Outsloped, Neither):
Neither

Incline
(Flat,Slight,Moderate,Steep):
Slight/Moderate


Estimated Past Erosion:
Total Erosion
Total Yds
3 Yds
3/Foot
0.00 0.00


Estimated Future Erosion:
Area Erosion Rate Delivery Percentage Sediment Delivery
(A) (E) (D) in Yds
3 (Q
s)
67.00 0.03 .90
13.40

Rank Priority Based on Future Erosion (Q
s): 17


14
Road Name: Conifer Rd. Village: Woodacre Site Number: 4
Location: Stream Crossing located about 90' UH of site 3
Road Composition: NA Water Bars?: None
Length: NA Width: NA
Slope
(Insloped, Outsloped, Neither):
NA
Incline
(Flat,Slight,Moderate,Steep):
NA


Estimated Past Erosion:
Total Erosion
Total Yds
3 Yds
3/Foot
NA NA


Estimated Future Erosion:
Area Erosion Rate Delivery Percentage Sediment Delivery
(A) (E) (D) in Yds
3 (Q
s)
00.00 0.00 .00
0.00

Rank Priority Based on Future Erosion (Q
s): 20


Stream Crossings:
Crossing
#
Type: Length: Diameter: Inlet Open?
(OCPR):
Outlet Open?
(OCPR):
Estimated Fill
Prism (Blowout)
in Yds
3
:
SX4-1 CMP 35' 16" Partially
Plugged
O 700

15
Road Name: Conifer Rd. Village: Woodacre Site Number: 5
Location: Located Adjacent to site 4 and extends 534 feet to 100 Conifer
Road Composition: Dirt w/Gravel Water Bars?: None
Length: 534 Width: 10
Slope
(Insloped, Outsloped, Neither):
Slightly Outsloped

Incline
(Flat,Slight,Moderate,Steep):
Steep


Estimated Past Erosion:
Total Erosion
Total Yds
3 Yds
3/Foot
3307.42 4.80


Estimated Future Erosion:
Area Erosion Rate Delivery Percentage Sediment Delivery
(A) (E) (D) in Yds
3 (Q
s)
287.40 0.03 0.85
47.25

Rank Priority Based on Future Erosion (Q
s): 6


Stream Crossings:
Crossing
#
Type: Length: Diameter: Inlet Open?
(OCPR):
Outlet Open?
(OCPR):
Estimated Fill
Prism (Blowout)
in Yds
3
:
SX5A-1 CMP 35 16" Totally
Plugged
O 700

16
Road Name: Conifer Rd. Village: Woodacre Site Number: 6
Location: From 100 Conifer to Stream Crossing at sign the says "End of County Maintained Road
Road Composition: Dirt w/Gravel Water Bars?: None
Length: 470 Width: 9
Slope
(Insloped, Outsloped, Neither):
Neither

Incline
(Flat,Slight,Moderate,Steep):
Flat/Slight


Estimated Past Erosion:
Total Erosion
Total Yds
3 Yds
3/Foot
1033.82 2.21


Estimated Future Erosion:
Area Erosion Rate Delivery Percentage Sediment Delivery
(A) (E) (D) in Yds
3 (Q
s)
1226.30 0.03 1.00
24.07

Rank Priority Based on Future Erosion (Q
s): 13


Stream Crossings:
Crossing
#
Type: Length: Diameter: Inlet Open?
(OCPR):
Outlet Open?
(OCPR):
Estimated Fill
Prism (Blowout)
in Yds
3
:
SX6A-1 No
Culvert-
Drainage
flows over
road
17' 6" NA NA 2.81
17
Road Name: Salix Ave Village: Woodacre Site Number: 7
Location: Salix Road from the residences at #11 to #2
Road Composition: Pavement (25-30% degraded) Water Bars?: None
Length: 283 Width: 12
Slope
(Insloped, Outsloped, Neither):
Slightly Outsloped

Incline
(Flat,Slight,Moderate,Steep):
Slight/Moderate


Estimated Future Erosion:
Area Erosion Rate Delivery Percentage Sediment Delivery
(A) (E) (D) in Yds
3 (Q
s)
82.71 0.02 1.00
24.01

Rank Priority Based on Future Erosion (Q
s): 14


Stream Crossings:
Crossing
#
Type: Length: Diameter: Inlet Open?
(OCPR):
Outlet Open?
(OCPR):
Estimated Fill
Prism (Blowout)
in Yds
3
:
SX7B-1 Plastic 17' 3'3" O O 1785
18
Road Name: Upper Carson Rd. Village: Woodacre Site Number: 8
Location: Top of Carson Rd at open space gate downhill for 550 feet to short section of pavement.
Road Composition: Partial pavement & partial dirt Water Bars?: None
Length: 550 Width: 9
Slope
(Insloped, Outsloped, Neither):
Insloped w/small section that is neither

Incline
(Flat,Slight,Moderate,Steep): Flat to Steep


Estimated Past Erosion:
Total Erosion
Total Yds
3 Yds
3/Foot
350.70 0.50


Estimated Future Erosion:
Area Erosion Rate Delivery Percentage Sediment Delivery
(A) (E) (D) in Yds
3 (Q
s)
349.60 0.02 0.80
21.37

Rank Priority Based on Future Erosion (Q
s): 15


Stream Crossings:
Crossing
#
Type: Length: Diameter: Inlet Open?
(OCPR):
Outlet Open?
(OCPR):
Estimated Fill
Prism (Blowout)
in Yds
3
:
SX8D-1 CMP 15' 10" O - partly
blocked
O 52.65

19
Road Name: Upper Carson Rd. Village: Woodacre Site Number: 9
Location: From section of pavement to intersection of Carson, Conifer and Upper Carson.
Road Composition: Gravel w/Dirt Water Bars?: None
Length: 433 Width: 10
Slope
(Insloped, Outsloped, Neither):
Insloped w/small section that is neither

Incline
(Flat,Slight,Moderate,Steep):
Flat to moderate


Estimated Past Erosion:
Total Erosion
Total Yds
3 Yds
3/Foot
407.27 1.12


Estimated Future Erosion:
Area Erosion Rate Delivery Percentage Sediment Delivery
(A) (E) (D) in Yds
3 (Q
s)
129.31 0.03 0.80
35.17

Rank Priority Based on Future Erosion (Q
s): 10


20
Road Name: Conifer Rd. Village: Woodacre Site Number: 10
Location: From 189 Conifer downhill 204 feet.
Road Composition: Dirt w/Gravel Water Bars?: None
Length: 204 Width: 9
Slope
(Insloped, Outsloped, Neither):
Neither

Incline
(Flat,Slight,Moderate,Steep):
Moderate


Estimated Past Erosion:
Total Erosion
Total Yds
3 Yds
3/Foot
62.70 0.31


Estimated Future Erosion:
Area Erosion Rate Delivery Percentage Sediment Delivery
(A) (E) (D) in Yds
3 (Q
s)
67.32 0.03 0.80
15.72

Rank Priority Based on Future Erosion (Q
s): 16


21
Road Name: Conifer Rd. Village: Woodacre Site Number: 11
Location: From intersection of Conifer and Fir to end of Mari and Rich's house
Road Composition: Gravel w/Dirt Water Bars?: None
Length: 168 Width: 9
Slope
(Insloped, Outsloped, Neither):
Neither

Incline
(Flat,Slight,Moderate,Steep):
Flat


Estimated Past Erosion:
Total Erosion
Total Yds
3 Yds
3/Foot
0.00 0.00


Estimated Future Erosion:
Area Erosion Rate Delivery Percentage Sediment Delivery
(A) (E) (D) in Yds
3 (Q
s)
1352.00 0.02 0.30
6.36

Rank Priority Based on Future Erosion (Q
s): 19


22
Road Name: Hill Rd. Village: Woodacre Site Number: 12
Location: From intersection of Hill and Central going uphill on Hill.
Road Composition: Dirt w/Gravel Water Bars?: None
Length: 824 Width: 9
Slope
(Insloped, Outsloped, Neither):
Insloped

Incline
(Flat,Slight,Moderate,Steep):
Moderate


Estimated Past Erosion:
Total Erosion
Total Yds
3 Yds
3/Foot
2361.67 1.67


Estimated Future Erosion:
Area Erosion Rate Delivery Percentage Sediment Delivery
(A) (E) (D) in Yds
3 (Q
s)
688.74 0.03 1.00
62.59

Rank Priority Based on Future Erosion (Q
s): 5


Stream Crossings:
Crossing
#
Type: Length: Diameter: Inlet Open?
(OCPR):
Outlet Open?
(OCPR):
Estimated Fill
Prism (Blowout)
in Yds
3
:
SX12B-1 CMP 20' 12" O O 192
23
Road Name: East Cintura Ave. Village: Lagunitas Site Number: 13
Location: From intersection of East Cintura, Rodeo and La Cuesta downhill for 1054 feet
Road Composition: Dirt with Gravel Water Bars?: 4
Length: 1054 Width: 9
Slope
(Insloped, Outsloped, Neither):
Mostly Insloped

Incline
(Flat,Slight,Moderate,Steep):
Moderate


Estimated Past Erosion:
Total Erosion
Total Yds
3 Yds
3/Foot
553.18 0.53


Estimated Future Erosion:
Area Erosion Rate Delivery Percentage Sediment Delivery
(A) (E) (D) in Yds
3 (Q
s)
381.93 0.03 1.00
65.84

Rank Priority Based on Future Erosion (Q
s): 4


Stream Crossings:
Crossing
#
Type: Length: Diameter: Inlet Open?
(OCPR):
Outlet Open?
(OCPR):
Estimated Fill
Prism (Blowout)
in Yds
3
:
SX13C-1 CMP 15' ~8" O - Partially
Compressed
O 900

SX13D-1 CMP 28' 10" O - Partially
Compressed
O 840
24
Road Name: Village: Lagunitas Site Number: 14
Location: From intersection of East Cintura, Rodeo and La Cuesta
Road Composition: Gravel (newly laid down road bed) Water Bars?: None
Length: 391 Width: 9
Slope
(Insloped, Outsloped, Neither):
Insloped and Neither

Incline
(Flat,Slight,Moderate,Steep):
Slight


Estimated Past Erosion:
Total Erosion
Total Yds
3 Yds
3/Foot
252.84 0.66


Estimated Future Erosion:
Area Erosion Rate Delivery Percentage Sediment Delivery
(A) (E) (D) in Yds
3 (Q
s)
122.06 0.02 1.00
24.31

Rank Priority Based on Future Erosion (Q
s): 12


Stream Crossings:
Crossing
#
Type: Length: Diameter: Inlet Open?
(OCPR):
Outlet Open?
(OCPR):
Estimated Fill
Prism (Blowout)
in Yds
3:
SX14B-1 CMP 15' 8" Partially
Compressed
Partially
Compressed
20.1

SX14B-2 CMP 15' 8" Partially
Compressed
O 56.46
25
Road Name: Rodeo Ave Village: Lagunitas Site Number: 15
Location: From intersection of Rodeo and Lucie Lane going downhill for 888 feet.
Road Composition: Dirt Water Bars?: None
Length: 888 Width: 9
Slope
(Insloped, Outsloped, Neither):
Insloped and Outsloped

Incline
(Flat,Slight,Moderate,Steep):
Slight/Moderate


Estimated Past Erosion:
Total Erosion
Total Yds
3 Yds
3/Foot
1528.94 1.10


Estimated Future Erosion:
Area Erosion Rate Delivery Percentage Sediment Delivery
(A) (E) (D) in Yds
3 (Q
s)
360.00 0.03 1.00
69.81

Rank Priority Based on Future Erosion (Q
s): 3


Stream Crossings:
Crossing
#
Type: Length: Diameter: Inlet Open?
(OCPR):
Outlet Open?
(OCPR):
Estimated Fill
Prism (Blowout)
in Yds
3
:
SX15A-1 CMP 19 O O 137.0
SX15B-1 39 O O 175.5
26
Road Name: Rodeo Ave Village: Lagunitas Site Number: 16
Location: Adjacent to site 15 down to Alta
Road Composition: Dirt w/Gravel (pavement on last 67' next to Alta) Water Bars?: 1
Length: 467 Width: 9
Slope
(Insloped, Outsloped, Neither):
Slightly Outsloped

Incline
(Flat,Slight,Moderate,Steep):
Moderate


Estimated Past Erosion:
Total Erosion
Total Yds
3 Yds
3/Foot
326.00 0.40


Estimated Future Erosion:
Area Erosion Rate Delivery Percentage Sediment Delivery
(A) (E) (D) in Yds
3 (Q
s)
338.72 0.03 1.00
45.22

Rank Priority Based on Future Erosion (Q
s): 7


Stream Crossings:
Crossing
#
Type: Length: Diameter: Inlet Open?
(OCPR):
Outlet Open?
(OCPR):
Estimated Fill
Prism (Blowout)
in Yds
3
:
SX16A-1 Storm
drain, with
grate over
top
8 O O 16

27
Road Name: La Vuelta Rd. Village: Lagunitas Site Number: 17
Location: From intersection of Rodeo and La Vuelta downhill for 920 feet.
Road Composition: Dirt with Gravel/Paved Water Bars?: 2
Length: 920 Width: 9
Slope
(Insloped, Outsloped, Neither):
Insloped and Outsloped

Incline
(Flat,Slight,Moderate,Steep):
Slight/Moderate


Estimated Past Erosion:
Total Erosion
Total Yds
3 Yds
3/Foot
76.63 0.19


Estimated Future Erosion:
Area Erosion Rate Delivery Percentage Sediment Delivery
(A) (E) (D) in Yds
3 (Q
s)
272.00 0.03 1.00
84.80

Rank Priority Based on Future Erosion (Q
s): 2


28
Road Name: East Cintura Ave. Village: Lagunitas Site Number: 18
Location: Adjacent to 13D going downhill 570 feet.
Road Composition: Gravel w/Dirt Water Bars?: 3
Length: 570 Width: 9
Slope
(Insloped, Outsloped, Neither):
Insloped and Neither

Incline
(Flat,Slight,Moderate,Steep):
Slight/Moderate


Estimated Past Erosion:
Total Erosion
Total Yds
3 Yds
3/Foot
134.26 0.28


Estimated Future Erosion:
Area Erosion Rate Delivery Percentage Sediment Delivery
(A) (E) (D) in Yds
3 (Q
s)
519.02 0.02 1.00
35.47

Rank Priority Based on Future Erosion (Q
s): 9


Stream Crossings:
Crossing
#
Type: Length: Diameter: Inlet Open?
(OCPR):
Outlet Open?
(OCPR):
Estimated Fill
Prism (Blowout)
in Yds
3
:
SX18A-1 CMP 16 O O 75.84
29
Road Name: Potrero Rd. Village: Lagunitas Site Number: 19
Location: From intersection of East Cintura, La Vuelta and Potrero going uphill on Potrero 746 feet.
Road Composition: Gravel w/Dirt Water Bars?: 1
Length: 746 Width: 9
Slope
(Insloped, Outsloped, Neither):
Outsloped, Insloped & Neither

Incline
(Flat,Slight,Moderate,Steep):
Slight to Steep


Estimated Past Erosion:
Total Erosion
Total Yds
3 Yds
3/Foot
6062.36 2.72


Estimated Future Erosion:
Area Erosion Rate Delivery Percentage Sediment Delivery
(A) (E) (D) in Yds
3 (Q
s)
895.22 0.03 1.00
41.94

Rank Priority Based on Future Erosion (Q
s): 8


Stream Crossings:
Crossing
#
Type: Length: Diameter: Inlet Open?
(OCPR):
Outlet Open?
(OCPR):
Estimated Fill
Prism (Blowout)
in Yds
3
:
SX19A-1 CMP 20' 18" O O 320
SX19B-1 CMP 28' 12" O O 84
SX19C-1 CMP 36' 12" O O 162
30
Road Name: Aztec Rd. Village: Forest Knolls Site Number: 20
Location: From intersection of Guadalupe and Aztec uphill for 2021 feet.
Road Composition: Dirt w/Gravel (Some Pavement) Water Bars?: None
Length: 2021 Width: 9
Slope
(Insloped, Outsloped, Neither):
Neither

Incline
(Flat,Slight,Moderate,Steep):
Flat to Moderate


Estimated Past Erosion:
Total Erosion
Total Yds
3 Yds
3/Foot
2107.76 0.69


Estimated Future Erosion:
Area Erosion Rate Delivery Percentage Sediment Delivery
(A) (E) (D) in Yds
3 (Q
s)
1270.64 0.03 1.00
102.37

Rank Priority Based on Future Erosion (Q
s): 1


Stream Crossings:
Crossing
#
Type: Length: Diameter: Inlet Open?
(OCPR):
Outlet Open?
(OCPR):
Estimated Fill
Prism (Blowout)
in Yds
3
:
SX20A-1 Plastic 57 8 1/2 Plugged O 114
SX20A-2 Plastic 40 8 3/4 Plugged O 80
SX20A-3 Plastic 15 8 O Crushed 30
SX20A-4 Plastic 12 6 Not Visible O 24