Boggs Mountain Demonstration State Forest Draft ... - Cal Fire

Boggs Mountain Demonstration State Forest Draft Management Plan, June 2008
Upper Spikenard Creek:
The crossing at Upper Spikenard Creek has a 36” (3’) culvert, and measures 4’ from the base of
the culvert to the headwall, and 5’ to the road grade. The headwater depth is 1.7 culvertdiameters.
A=96 acres L= 1100 feet (.2 miles) H= 500 feet
Tc= [11.9(.2) 3 /500] .385 = .037 hours (2.2 minutes)
Q= .4(1.86)96
= 71.4 cfs
The suggested culvert size for Upper Spikenard Creek was determined to be 38”.
Malo Creek:
The crossing at Malo Creek has a 36” (3’) culvert, and measures 14’ from the base of the culvert
to the headwall as well as to the road grade. The headwater depth is 4.7 culvert-diameters.
A= 96 acres L=2484 feet (.47 miles) H= 460 feet
Tc= [11.9(.47) 3 /460] .385 = .102 hours (6.1 minutes)
Q= .4(1.86)96
= 71.4 cfs
The suggested culvert size for Malo Creek was determined to be 29”. Since the present culvert
size is 36”, and there is a very high headwall, the crossing at Malo Creek is probably adequate to
withstand the 100-year flood flow.
Houghton Creek:
The crossing at Houghton Creek has a 24” culvert (2’).
A= 134 acres L= 1000 feet (.2 miles) H= 80 feet
Tc= [11.9(.2) 3 /80] .385 = .07 hours (4.5 minutes)
Q= .4(1.86)134
= 99.7 cfs
84