caliifornia geology magazine nov-dec 1993

8/7/2019 Caliifornia Geology Magazine Nov-Dec 1993

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RUNOFF AND EROSION AFTER THEOAKLAND FIRESTORM _.. _ _ _ _ _ _ 159EMERGENCY LANDSLIDE HAZARD EVALUATIONFOLLOWING THE TUNNEL FIRE, OCTOBER 19-23, 1991 174DMG SPECIAL PUBLICATION 113 RELEASE _ _ 179TEACHER FEATURE _ __ _ 180CALIFORNIA'S ROCKS, MINERALS, AND DECORATIVESTONES USED BY NATIVE AMERICANS 182DMG PUBLICATIONS REQUEST FORM _ 183CALIFORNIA GEOLOGY SUBSCRIPTION AND CHANGEOF ADDRESS FORM _ _._ _ _ _ 184CONFERENCE NOTES ._ _ _ 184INDEX TO VOLUME 46 - 1993 _ _ _.._.. 185LITERARY PROSPE:CTS _ _ _ _ 186

CALIFORNIAGEOLOGY

A PUBLICATION OF THEDEPARTMENT OF CONSERVATIONDIVISION OF MINES AND GEOLOGYState 01 California PETE WILSONGovernorThe Resources Agency DOUGLAS P. WHEELERSecretary for ResourcesDepartment of Conservation EDWARD G. HEIDIGDirectorDivision 01 Mines 1\ Geology JAMES F. DAVISState Geologist

I I e

CALIFORNIA GEOLOGYEditor:Art Director:Publications Supervisor:

Elise MattisonPeggy WalkerJeff Tambert

British Geological Survey (BGS)Hosts Conference

April 1994Division Headquarlers:801 K Street. 12th Floor. MS 12-30Sacramento. CA 95814-3531(916) 445-1825Publications and Information Olt,ce:801 K Street. 14th Floor. MS 14-33Sacramento. CA 95814-3532(916) 445-5716Southern Cahlornia Regional Ofhce:107 South Broadway. Room 1065Los Angeles. CA 90012-4402(213) 620-3560Bay Area Regional Office:185 Berry Street. Suite 3600San Francisco. CA 94107(415) 904-7707CALIFORNIA GEOLOGY (ISSN 0026 4555) Is p u b l i s ~ e d bimonthly by the Department of Conservation, Division of Minesand Geology. The Records Office is at 1059 Vme Street. SUite103. Sacramento. CA 95814. Second class postage IS paid atSacramento. CA. Postmaster: Send address changes to CALiFORNIA GEOLOGY (USPS 350840). Box 2980. Sacramento.CA 95812-2980Reports concerning Division of Mines and Geology proJects,and articles and news items related to the anh sciences inCaJlforma. are Included in the magazine. Contributed articles.photographs. news lIems, and geological meet' g announcemen1s are welcome.THE CONCLUSIONS AND OPINIONS EXPRESSED IN ARTICLES ARE SOLELY THOSE OF THE AUTHORS AND ARENOT NECESSARILY ENDORSED BY THE DEPARTMENTOF CONSERVATION.Correspondence should be addressed to: Edl or.CALIFORNIA GEOLOGY. 801 K Street. MS 1433.Sacramento, CA 95814-3532SUbscriptions: SlO.OOil yr. (6 ,ssues); 519.0012 yrs. (12 issuesl:$28.003 yrs. ( 8 Issues). Send subscnptoon orders andchange of address information to CALiFORNIA GEOLOGY.P. O. Box 2980. Sacra ento. CA 95812-2980.

NOVEMBER;DECEMBER 1993 Volume 46fNumber 6CGEOA 46 (6) 157-188 (1993)

The e meeting are organized by the Inst i tu t ion of Mining and Metallurgyand associated with the International n ion o f Geological Sciences ( lUGS)/U ESea Deposit Mo d lIing Program. Th e will be held in Keywor th.lo tt ingham. United Kingdom. Th conference will focus on the hypothesistha t pat ia l assoc ia tion of ore depos it s a re t o some exten t d ic ta ted by theinhomogeneous di t r ibut ion of elements in the ear th 's crust. Where ore-formi ng e lements are of lov natura l abundance 10 ppm). evaluat ion of crustalre ervoirs relatable to areas of potential enhanced mineralization will requireassessment of the varia tion in background levels.Models for M ineral Depos i ts in Sedimentary Basins: Apr il 1 3 and 14 , 1994BGS Mineral s Indus tr y Forum II: Apr il 15. 1994BG S Short Courses : Mul tidataset analys is methods for m inera l explorationand deposit model l ing; Indus tr ial m inera l deposit evaluat ion; Environmenta l geochem ist ry and m ine deve lopmen t : moni to ri ng and remediat ion :Apr il 12, 1994For more info rmation. contact:

The Conference OfficeThe Inst itut ion of Mining and Metallurgy

44 Portland PlaceLondon W1 N 4BR. United Kingdom'fi" (071 5803802FAX: 071 4365388

Some copie of the September/October issue of CALIFOR IAGEOLOGY were printed with blank or overprinted page . If youreceived a copy and have not had it replaced. please call the Publi-cations and Information Office, (916) 445-5716. and it will bereplaced free of charge.

Cove r Pho to : Residential area after the Oakland Hills fire.Photo by Harold Adler. Berkeley, California.

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Figure 1. San Francisco Bay Area. Orange rectangle apprQ)umates area In Photo 1.

most expensive post-fire erosion controlproject in California's history.Urban growth and nre suppressionhave led to a high potential for destructive fires at the urban/wildland interface. With the continued expansion ofurban lands into the highly flammablewildlands of California. the potential forsuch nre is il1creasing. The BerkeleyFire of 1923. which swept down towardSan Francisco Bay on a similar day ofhot dry winds from the Central Valley.destroyed 584 homes and served as awarning. More recently. the SantaBarbara Paint Fire in 1990. which

burned 4.900 acres (1.980 hectares)and destroyed 641 homes. and SantaBarbara's 1977 Sycamore Fire. whichburned 804 acres (325 hectares) anddestroyed 234 homes. illustrate therisk of living at this interface. Whilemuch discussion and planning is underway to provide better fire response andreduce the risk of catastrophic fire. littlehas been done to assess the need andeffectiveness of costly post-bum temporary erosion-control measures. Thisproblem is not. of course. limited to the

urban/wildland interface. California hasextensive forest fires. such as the onethat burned 600.000 acres (242.915hectares) in 1987The issue of accelerated erosionaffecting downstream resources israised following each fire. There is agrowing trend toward intervention. ofimplementing engineering solutions tocontrol natural processes. Althoughstate and federal laws require immediatepost-fire erosion control elfons to bedeveloped on public lands. there is agrowing debate about the need andeffectiveness of such commonly used

measures as grass seeding and temporary straw bale check dams like thoseused after the Oakland fire. In fact.some evidence suggests that grass seeding can be counterproductive (Krammesand Hill. 1963: Rice and others. 1969:Rice and Foggin. 1971: Conrad. 1979:Gautier, 1983; Nadkarni and Odion.1986: Barro and Conard. 1987: Milesand others. 1989: Taskey and others.1989; Conard and others. 199 L Libbyand Rodrigues. 1992: Booker and others. 1992),

We presenl an analysis 01 expecta-tions. and observations of the runoffand erosional response to the Oaklandfirestorm as modified by erosion controlmeasures. Our goal is not to second-guess the measures taken under emergency conditions. but rather to offero b ~ r v a t l o n s and recommendations thatcould prove useful in deciding appropri-ate responses to inevitable fires. Ourfundamental point is that erosionalresponse to fire varies greatly in a rec-ognizable way based on lactors such asgeology. topography. climate. and landuse. Costly temporary erosion controlmeasures in some cases 01 wildland lireappear unnecessary and may even becounterproductive.

THE SOUTHERNCALIFORNIA MODEL

The erosional response 01 burnedlands to winter storms in canyon landsin southern California has been welldocumented (Barro and Conard. 1991;Rice. 1982: Wells. 1981. 1987). andhas commonly been referred to as the~ f i r e f l o o ( r sequence. Immediately aftera fire. and in son1e cases during thefire. as organic debris dams are incinerated. debris and coarse sedimentsllow downslope into channels. washes.and gullies accentuating a processcalled'dry raver (Anderson and others.1959: Wells. 1981: Rice. 1982). Theprocess 01 dry rawl is most closely associated with very steep slopes underlainby granitic rocks or coarse-grainedsandstones in areas that are tectonically active and undergoing rapid upliftresulting in background erosion ratesas high as 0.06 to 0.09 inches (14 to2.3 mm) per year (Wells. 1986; ScOlland Williams. 1978). [n parts 01 southern California. the process of dry ravel.independent of fire. accounlS lor halfof all hillside erosion (Anderson andothers. 1959: Krammes. 1965: Rice.1974. Howard. 1982). Ongoing studiesin the Calilornia chaparral wildlandsdemonstrate that dry ravel and. to alesser extent. the formation of extensiverill networks account lor most of theincreased sediment production follOWinga nre (Wells. 1986).

Fires can also vaporize organic compounds within the burning vegetation.The vapor moves through the soil to adepth where il will condense. forming

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Figure 2 Predicted hillSide response: hydrophobIc SOilspromoting excessive overland !low, the development of afill network. and a large increase in the sediment toad.

a water repellent layer. or hydrophobicsoH (DeBano. 1981. Savage. 1974).This water repellency is strongest incoarse soils (DeBano. 1981), and canproduce increased runoff and sedimentloading through the development of anextensive rill network (Wells. 1986)(Figure 2). The increased flow to channels during periods of intense rainfallcan mobilize sediment and debrisslored in the channel. as a debris now.or what was originally thought of asa debris flood. hence the term ~ f i r e flood" sequence. However. work doneby Florsheim and olhers (1991). following the 1985 Wheeler Fire nearSanta Barbara. sug-gests Ihat

of fire history and post-fire erosionalresponse in the East Bay Hil ls. howcould we assess the likelihood of possible catastrophic response to theOctober 20.1991 Oakland fire?

We could start by looking lo r similaritiesin landscape between southern California and the Oakland Hills that suggest adebris flow/"fire-llood" response couldbe possible (Table 1).

The immediate evidence. especiallyin the critical areas of slope. solis. background erosion rate. and most importantly rainfall intensity. suggests thatthese two areas are very different. It

does not suggest that processesthought to be common to landscapes in southern California should apply 10 a verydifferent landscape in

the Oakland Hills.A reconnaissance of the

OaklandHills burnarea on

normal fluvial transport 01 these sediments is more l ikely. According toRorshcim and olhers (1991). moderatestorm events Ihal CQuld mobilize sediments aTe far more l ikely to occur thanthe large magnitude. high intensitystorm events that would generate largedestructive debris flows. More recently.the 14.900 cubic yards (I 1.400 m 1of sediments deposited in debris basinsfollowing the 1990 Santa Barbara PaintFire were also a result of normal fluvialtransport of ravel derived sediments.rather than debris flow (David Valentine.U.c. Santa Barbara. oral communication. 1993),

WILL THE "FIRE-FLOOD"SEQUENCE OCCUR

IN THE OAKLAND HILLS?Although at least 14 wildfires haveoccurred In the East Bay Hil ls since

1923. no written record or fieldevidence of catastrophic erosionalresponse to fire has been found. If weapproach Ihe problems of hazard andrisk assessment without any knowledge

Table' Warershed Parameters for Southern Callforma and rhe Oak.land HillsPARAMETER COASTAL SOUTHERN OAKLAND HILLS

CALIFORNIA ~ F I R E F L O O D " FIRE AREA WATERSHEDSWATERSHEDS

Max. Relief 9,184 feet (2.800 m) 1.100 feet (335 m)Slope Ave: 65%; Max: >100% Ave: 35%: Max: 90%(Wells, 1981)Watershed 1 km 2 " 13 km2


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October 22. 1991. immediately afterthe fire. and again on October 25.1991. after the first storm of the season.showed lillie evidence of natural rillingexcept from road runoff. Significantpiles of ravel OIl the bases of slopes orin the channels were not evident.

At a weather station 3 miles (5 km)south of the fire area. rain for theOctober 25 storm was reported as75 mm (2.96 inches) during 13 hours(a 10-year return interval [Rantz. 1971 I)wilh maximum intensities of 30 mm perhour (1.2 inches/hour) for a 6-minuteinterval. A stalion 1.2 miles (2 km) northof the fire area reported 34 mm (1.34inches) (a 2-year return intervallRantz.19711) during 13 hours of rainfall andmaximum intensities of 7 mm (0.28inches) per hour for a 7-minule interval.Raveling and rill development are usuallyinitiated early on. and if they are notevident after the first significant storm.the likelihood that they will developdecreases as the winter progresses(Wells. 1986).

The 1985 Lexington Are burned13.800 acres (5.585 hectares) about6 miles (10 km) south of San Jose.Although this fire is closer geographically to Oakland. geomorphology andclimate are still very different. Runofffrom early winter storms developed arill network in the poorly consolidatedhighly fractured shales and interbededsandstones. Most of these rills developedduring storms between October andDecember 1985. after about 12 inches(300 mm) of cumulative rainfall. This isabout 30 percent of the mean annualrainfall for Ihe area (30 to 48 inches[760 to 1.220 mml depending on elevation) (Rantz. 1971). Few rills developedafter December. despite an additional51 inches (1.300 mm) of rain in early1986 (Keefer and others. 1986).The total rainfall of 63 inches (1.600mm) is about 300 percent of normal forthe Oakland Hills area (22 inches or560 mm per year). Despite the largeamount of runoff. burned slopes yieldedlillie sediment. In fact. Ihe response wascontrary to the popular notion of howa burned landscape should respond following a fire; there was no evidence ofa Mfire_floodMresponse. or of significantlandsliding (Keefer. and others).

ESTIMATION OF EROSIONPOTENTIALSlope response similar to the southern California "fire-flood" sequenceoutlined In Figure 2 was predicted because of the identification of hydrophobic soils in the Oakland Hills lire area'and the belief that rainlallintensities of2 inches (50 mm) per hour for as longas 3 hours (>1OO-year storm) were possible for the Oakland fire area (U.S.Department of Agriculture. Soil Conservation Service video of post-fire conditions. Octoher 24. 1991). Water repellency was evaluated by lhe SCS usingIhe standard water drop test. The limerequired for a large drop of water 10soak into the soil detennlnes its class ofhydrophobicity." Of the six wildland sites

tested. five showed evidence of hydro-phobicity. Hydrophobicity was mostpronounced in intensely burned eucalyptus groves. with slight 10 strong hydrophobicity evident in burnt stands ofMonterey pine, Subsequent tests showthese two vegetation types to be relatively equal in hydrophobic developmentbeneath healthy (unburned) stands.As a result of an anticipated increase

In runoff and erosion. an estimate ofpossible soil loss for the Oakland Hillswas 75 cubic yards per acre (142 m3/hectare) (unpublished Interagency TaskForce soil erosion treatment meetingnotes. October 24.1991). Conversely.geologists from the U.S. GeologicalSurvey (USGS) and the CaliforniaDepartment of Conservation's Divisionof Mines and Geology (DMG) (TomSpittler. oral communication) felt waterrepellent soils were discontinuous andthere was not a serious erosion hazardin the fireslonn area (see Spittler. thisissue).

MITIGATION EFFORTS AFTERTHE FIRESTORM

As a result of potential erosion estimates. 1.800 acres (720 hectares) ofthe bum area were Initially seeded by air(29 pounds per acre or 32 kg!hectare)on October 23 and 24. 1991. The seedmixture consisted of six species. three ofwhich are not natives: California softchess (Bromus mollis). Hykon rose"ow Howell. 5011 Consllrvat,on $efVll;e,Wflnen communication. 1991,

clover (Trifolium hirfum). and Zorroannual fescue (Festuca mega/ura).The three native species are Berkeleyblue wildrye (Elymus glaucus). California poppy (Eschscholzia cali/ornico).and native blue lupin (Lupinus ssp.)(Libby and Rodrigues. 1992). The firsts torm of the season was on October 25.1991. The burn area was reseeded aspart of a hydromulch application during November and December. 1991.Hydromulch was applied 10 morethan 500 acres (200 hectares) ofburned wildlands." Each acre received29 pounds (13 kg) of seed. 1.000pounds (455 kg) of paper mulch. 500pounds (227 kg) of wood fiber. and110 gallons (4161) of acrylic copolymerglue. at a cost of approximately $1.750per acre ($4.325/hectare) (InternationaiErosion Control Association. 1992).

In addition. 1.700 straw bale checkdams were placed in gullies. channels.hollows. and landslide features in anallempt to moderate channel flow andhillside overland flow. Roadside areaswere treated with seed. straw mulchand the copolymer glue (lnlernationalErosion Control Association. 1992).Over 35 acres (14 hectares) of steephillsides overlooking buildings that survived the fire were treated with straw,fiber. and monofilament erosion blankets. and additional roadside areas weretreated with straw mulch (InternationalErosion Control Association. 1992). It isimportant to note that these Ireatmentshave only one purpose: to prevent Ihesurface loss of so il by overland flow. notmitigate the larger effects of landslides.

Additional engineered features suchas concrete and steel debris racks andsilt fences were installed. but these features were designed to mitigate erosion.nOI prevent it. Two small drainagebasins of 12 acres (5 hectares) or fewerwere extensively engineered. Slopeswere laid back. all remaining vegetationwas removed. and the incised channelswere filled with soil and then resurfaced.one with monofilament erosion mats."The nU"Tlber 01 acres l,eated w,th Ilydromulch 'san a ~ t r a p o l a l l o n denVfld trom lOtal quantll,es otproducts (Woodward Clyde Col'lSUlUlnts Inc..1992. YKleo about erosion control response).and the reCIpe tor hydromulch used '1'1 theOakland fire response (International ErOSiOnConlrol ASSOCIation. 1992).

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Photo 2. Old landslide anddebris flow scars shown byarrows (some associatedWithroad runoll) are revealed following the loss of vegetativecover in the Oakland Hills lireThese slopes have beentreated with a hydromulchapplication of seed. mulchedpaper. wood tiber. and acryliccopolymer glue.

SLOPE FAILURE AND FIREAfter the fire. the vegetation-freelandscape offered a dear view of thenumerous landslide scars that hadformed during previous years (Photo 2).These landslides. mostly slides. slumps.and flows. contrast with the ~ f i r e - f 1 o o d ~debris flows that are generated in steepcanyon bottoms in freshly depositedravel. Most are relatively shallow slopefailures that occur following increases inground saluration. Shallow soil slides candevelop into fast moving debris flows ofsaturate

fire plants resprouted. The dominantbrush species. coyote brush {BacharrispHu/arisJ. was able to crown sproutfollowing the fire. Bluegum eucalyptustrees. introduced to the Oakland Hillsin the early 19005. are being cut downby homeowners and public agenciesbecause many think they are responsiblefor the rapid spread of fire. The stumpsare starting to resprout so it is notknown how their root strength will beaffected. Monterey pines. which wereintroduced at the same lime, did notsurvive the fire, and their root deterioration will continue over several years.

In the event of a severe loss of rootstrength in fire-damaged plants. reseeding Oakland hillsides with grasses wouldnot prevent landsliding. The shallowlandslide features common to the Oakland Hills typically have failure planesbelow the rooting zone of grasses. Wethink that heavy densities of reseededgrasses would only increase infiltration.and therefore soil moisture.

LANDSLIDE MAPPINGAND REBUILDING

Consultants contracted by the Cityof Oakland counted 184 scarps or othergeomorphic features thought to be associated with landslides within the burnarea. prompting city employees to mapexisting and potential failure sites. The

consultants issued a draft report. inwhich the probability and consequenceof a landslide failure were evaluated ateach identified feature. and a relativemeasure of risk was calculated for eachaffected area in terms of the probabilityof significant damage to public or private properties. This report was usedby the City of Oakland in the development of a management plan to revisebuild-ing permit policy in order to address these landslide risks. Although themapping and assignment of hazardprobability can be debated. the City ofOakland deserves credit lor developinga planning 1001 of this kind. Eventhough development of the plan wasfacilitated by the exposure of the landscape by fire. this type 01 managementplan is beneficial at any time. becauseof the chronic landslide hazard in theOakland Hills.

BURN AREA OBSERVATIONS:MONITORING PROGRAM

To evaluate the effectiveness of theerosion control measures and to analyzehow wild/ires influence runoff and erosion processes in the Oakland Hills. wemonitored winter runoff and erosion onseveral small erosion plots established inthe upland areas of the bum. During lhesummer of 1992. the number of erosion plots was increased. and runoff anderosion were measured during several

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controlled artificial rainstorm experiments, Sprinkler experiments allowed amore detailed analysis of runoff anderosion mechanisms and provided abroader range of rainfall intensities thanoccurred in a normal winter (Meyer andMcCune. 1958: Selby. 1970; Birk andothers. 1979: Dunne and others. 1980;Imeson and others. 1992).

Given the emergency status and timeconstraints of the project. it was notposSible to install and monitor a largenetwork of observation points, Instead.we focused on collecting field data andunderstanding processes at representative sites. These observations weresupplemented by extensive inspection ofthe burn area during storms.

Seven plots were established onslopes of 30 to 40 degrees for wintermonitoring in four drainage basins inwildland areas of the Oakland Hills,Sleeper than average slopes wereselected because they are typical ofslopes found in southern California,and because erosion will be greatest onthese steeper slopes. Five plots were inthe lire area. and two in an unburnedcanyon adjacent to the burn. Plots wereestablished on soils Irom the two predominant parent materials. chert andsandstone (gravelly loam and loamsoils), and on hydromulch-treated anduntreated slopes. The pre-fire vegetationtypes for these plots were predominantlyeucalyptus and Monterey pine. whichare associated with the water repellentsoils found in the fire area. Plots wereapproximately 15 feet (4.5 mllong by5 feet (1.5 m) wide. with sheet metalboundaries. A covered trough at thedownslope end trapped sediment anddirected overland flow to a storage container (Photo 3), Seven additional plotswere constructed on sites with similarconditions during the summer of 1992for the simulated rainfall experiments.Winter of 1991-92

Rainfall for each plot was monitoredusing rain gauges at each site, Rain-fall intensily was monitored throughthe Alameda County Flood ControlDistrict's ALERT network. and reportedin I-mm- (0.04-inch-) per-minute increments, Two stations were used. one 1.2miles (2 km) north of the bum area. anda new stalion established in the fire area.

There were 14 storms between Januaryand April. 1992. with none el


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Table 2 Runoff for Seven Sites Followmg the Fire January-Apri l 1992SITE VEGETATION SOIL TEXTURE HYDRO. MEAN MAX.MULCHED RUNOFF RUNOFFMJ Monterey pine loom 00 11.4% 23%

and brushM2 Monterey pine loom ye, 1.4% 3%

and brushVNI eucalyptus loom 00 13.8% 24%GWI eucalyptus gravelly 100m ye, 2.9% 5%GW2 eucalyptus gravelly loom 00 4.9% 7%(VI eucalyptus gravelly loom control 1.8% 5%unburnt(V2 hardwoods gravelly loom control 1.0% 3%and eucalyptus unburnt

surface-lowering of about 0.004 inch(0.1 mml during the winter. Thisamount is much smaller than the equivalent soil loss of 0.6 inch (14 ntm)predicted by the interagency task force(l991) (Figure 3).

There was an overall decrease insediment loss on all plots (treated. untreated. and control) through the winter.even though the largest Storm eventscame later in the season. Similar resultswere noted In Colorado by Morris andMoses (1987). This observation suggeststhat sediment loss in the Oakland Hillsis a function of sediment availability.rather than solely of potential runoff.Artilicial Rainlall Experiments

Because the winter immediately afterthe fire did not provide an opportunityto study the impact of a large storm onthe Oakland firestorm area, we decidedto simulate a lOO-year storm. Artificialsprinkler experiments simulating I-hourstorms. of between 1 and 2 inchesper hour (25 and 51 mm/hour) of rainfalL were conducted between July andOctober, 1992. Twenty artificial stormswere applied to 11 plots: three controlplots and eight burn plots. four of whichhad been monitored the previous win-

ter. It could be argued that site conditions the following summer would bevery different from those immediatelyafter the Oakland fire However. waterrepellent soils can be long lasting(DeBano. 1981). and we were able tofind sites that still had ash layers andwater repellent soils. and lacked understory vegetation. These additional sitesincluded two plots in a eucalyptus groveprescribe-burned during the 1992 summer, and had simllar soils and slopes tothose of the Oakland fire area.

Our sprinkler experiments wereconducted using two low-pressurenozzles mounted on trolleys and suspended from rails in a tubular aluminumframe. The frame stood about 10 feethigh by 6 feet wide by 20 feet long(3 m x 2 m x 6 m) and was centeredover the runoff and erosion plot (Photo4). 1lle nozzles were moved back andforth rapidly along the length of therails using a pulley system. so that asone nozzle was pulled up the plol. thesecond nozzle descended. Nozzles werechosen that best simulated natural rainstorm drop sizes and produced a precipitation intensity of between 1 and2 inches (25 and 51 mm) per hour. andhad the ability to cover the plot with arelatively even distribution of spray.

To estimate the average drop size forstorms here in the East Bay Hills. wecollected eight samples of natural raindrops using sifted white flour in a panduring three separate storms. The pansof flour were then baked. and the hardened raindrops sifted for size.Two artificial storms were appliedto most plots. and all vegetation wasremoved prior to the second sprink-ler experiment. Runoff as a result ofincreased precipitation intensities neverexceeded the winter maximum valuefor plots in the burn area. There was

in fact a decrease in runoff for all plotsIn reseeded areas. This decrease in runoff can be attributed to an increase ingopher activity providing additional subsurface flow paths. and to increasedinfiltration provided by the grass cover(Photo 5).

Sediment loss as a result of increasedprecipitation intensities was minimalwhen compared to the SCS estimatedequivalent soil loss of 0.6 inch (14 mm).The maximum sediment loss for a single1OO-year storm was about 50 per centof the lotal soil loss for the winter of1991. The cumulative net soil loss forall winter storms monitored and a singlesimulated 100-year event was only0.006 inch (0.15 mm). two orders ofmagnitude less than the equivalent maximum soil loss estimated by the SCS.Bioturbation

During the winter. a lattice of deertrails developed across the slopes. Animal tracks and disruption of soil androck fragments occasionally appeared inthe plots. When cleaning out sedimenttroughs after storms. it was obvious fromthe large particle size of some of thestored sediment. that some of the malerial was a result of this disturbance.As vegetation increased from thereseeding effort. gopher activity andtotal sediment flux within the plotsincreased. Previously undisturbed soliswere churned up. with mounds of loosesoil spilling downslope. and in somecases filling sediment troughs that hadremained empty during the previouswinter. This disturbance was most obvious in those areas that had a cover ofreseeded grasses. The measured sediment loss as a result of this bioturbation

CALIFORNIA GEOLOGY N O V E M B E ~ O E C E M B E R 1 ~'"


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Photo 6 Straw bale check dams or dikes are paced II I rows on an old landslide featureIn the foreground the hillSide has been trealed With lhe seed and hydromulch applicatlOflwhich was eventually sprayed over the enllre area

Photo 5, Reseeded plOI alter two Simulated storms (4 Inches Of 10 em of applied ramlall),The saturated surface hOrizon overlies a hydrophobic layer that IS mterrupted by verticallIow paths created by roots and gophers

The volume of sediment capturedbehind each straw bale check dam wasmeasured at the end of the winter rains.

Throughout the winter. we observedthe condition of 438 straw bale checkdams throughout gullies in two drainagebasins: Claremont Canyon RegionalPark (CCRP). which drains into Claremont Creek and then into San Francisco Bay; and the North OaklandSports Center (NOSC) watershed.which drains into Lake Temescal (PhotoIl. The CCRP watershed is a relativelynalurallandscape with a few hikingtrails and an urban boundary along itsupper perimeter with a continuousgully network emanating from urbanstonn drains. The NOSC watershedhas a similar urban boundary andstonn drain related gully network, butthe otherwise natural landscape is dis-sected by approximately a mile (2 km)of dirt roac:!.

bale dams on landslides and in hollowswere designed to trap sediment andincrease infiltration. thus furthering theopportunity for saturation. During sev-eral tours of the burn area. v.'e observedvery little sediment stored behind thesedams, supporting our estimates of mini-mal sediment transport by overlancll1owon these slopes.

Straw Bale Check DamsSeventeen hundred straw bale checkdams were placed in gullies and hol-lows. and on landslide scars and depos-its to moderate overland 1I0w and 10store sediment temporarily. The straw

sample was used to compare sites.Except for the first sampling period inJanuary. sites treated with hydromulchand the grass seed mixture always hada higher soil moisture content Ihanuntreated sites, By the end of March1992. soil moisture contents at treatedsiles (26 percent soil moisture) were.on the average. 23 percent higherthan those at sites with similar soilsthat received no treatment (t 9 percentsoil moisture), While the increased mois'ture content in the treated sites pointsto the success of the treatments in re-taining water and thus reducing over-land flow and potential surfaceerosion. il raises another issue. Manyareas thaI had landslide scars. or weresteep enough to generate landslides.received treatments of hydromu1ch.erosion mats. or straw bales. and pre-sumably would have had elevated soilmoisture conlents (Photo 6). Althoughthe moisture increase is relatively small.increasing soil moisture in potential slideareas decreases the amount of precipi-tation needed to cause landsliding, Ithas even been argued by some (Morton.1989) that burned slopes may be lesssusceplible to IandsIiding where signifkant overland 110w due to shallowwater repellency reduces soil moisturecontent,

CALIFORNIA GEOLOGY NOVEMBER,DECHABER 1993 ",


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CLAREMONT CANYON REGIONAL PARK The results of the straw bale analysisare shown in Figures 4a and 4b. If filledand unfilled dams are combined asMfunctioning properly." then by lateFebruary only 43 percent of the eCRPdams and 46 percent of the NOsedams were moderating sediment transport. By the end of March only 43 percent and 37 percent. respectively. werefunctioning. At the eCRP site. laborcrews repaired most of the dams afterFebruary storms. which most likelyaccounts for the consistent numberof functioning bales at this site. In theNOse watershed. no maintenance wasperformed on check dams within theupland gullies. However. several strawbale dams were replaced or repaired onan alluvial fan at the base of the uplandwatershed. Because the broad flat fanis a natural deposition zone. it was oneof the few sites where sediment couldbe quantified in subsequent winters.

Failedco. .U"d"'"NORTH OAKLAND SPORTS CENTER

,

"--..:=::===::====;---==-. FEB '92; N = 180 MAR '92; N = 191

..

40U.o ">-ZW( )a: "w"-

" ~ = = = = = : : : ; - - " " ' - - I FEB '92; N . 258 MAR '92; N = 248"

~ ::'u. "o>-zW oo( )a:W"-

..

,

Following the end of the first rainyseason. sediment volume behind thestraw bale check dams in gullies of theeCRP site was conservatively estimatedto be 73 cubic yards (56 m'" For theNOSe site. the volume 01 stored sediments within the gullies was about 71cubic yards (54 ml). and an additional162 cubic yards (124 m') was stored inthe alluvial fan for a total volume of 233cubic yards (178 m " The volume ofsediment deposited on the alluvial fanduring the second winter was estimatedto be 30 0 cubic yards (230 m'. an increase over the preceding winter eventhough slopes were fully vegetated withreseeded grasses. This change represents a 30 percent increase in sediment[fable 3) for the watershed and resultsfrom increases in rainfall during thesecond winter following the fire. gullying

CONDITION OF STRAW BALE CHECK DAMSFigures 4a and 4b. Percentage of functlomng and non-functionmg straw bale checkdams in two watersheds.

The dams were evaluated once duringFebruary 1992 and again at the end ofMarch 1992. Their condition was ratedas: 1) sidecut (water flowed around thedam thereby minimizing sediment storage): 2) undercut (water flowed beneaththe dam thereby minimizing sedimentstorage): 3) filled but cut (dam may havepartially or totally filled with sediment

but was subsequently undercut orsiclecut. so stored sediment is subsequently mobilized): 4) moved (dam isusually blown out by flows exceedingI cubic foot [0.03 mll per second. nosediment storage): 5) filled (unable tostore any additional sediment but stillallowing water to flow over the dam);6) unfilled (functioning properly).

Table 3. Volume of Stored Sed,ment In TwoGully Ne'works.Parameters CCAP Site NOSe SIteNllmber 01 dams '" N'D'oolOooge a,ea 40 aa&s 77 aeles

(016 km'J (031 km')Check dams 7J yd 71 yd '199192 (56 m (54 m])AlluvIal Ian 162 yd]199192 (124 m' lAlluvIal Ian 301 y


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Photo 7. Construction Imllated rilling and gullying. There was no erosion control at thiSsite in the burn area.

Table 4. 5011 Loss for Natural Slopes and Urbanized Watersheds In theOakland Hills

Site Undisturbed WatershedsSlopes Affected by

UrbanizationBackground erosion rate 0.08 mmlyr(Reneau. 1988) (0.003 irvyr)Erosion plots 1991-92 O.t mmlyr(0.004 inJyr)ErOSion plots 199t-92. plus 0,15 mmlyrSimulated 100 year storm (0,006 mtyr)NOSC straw bale SIIe 1991-92 0.6 mfTlJyr (0.024 in yr)NOSe straw bale site 1992-93 0.7 mmlyr (0.028 inlyr)Lake Temesca119071979 0.7 mmlyr (0.028 Inlyr)(Mahoney and others. 1979)MaXimum construction site 46.0 mm (1.8 in ) per sitesoitless (East Bay Regional Parlr.Distnct.1981)

post-fire reconstruction. In the secondwinter after the fire. construction andgrading operations were unabatedthroughout the burn area. Rilling wascommon. and many small failuresoccurred on freshly cut slopes. Duringrain storms. we observed streams ofsediment-laden water leaving construction sites and entering storm sewersand drainage channels (photo 7). Basedon estimates reported by the EaSI BayRegional Park District (EBRPD) in1981 for construction'induced erosionwithin the Lake Temescal watershed.sediment loading as a result of reconstruction following the Oakland fire isprobably 10 to 100 times greater thanbackground erosion rates (Table 4).Effectiveness of ErosionControl Procedures

The identification of the soil erosionhazard of hydrophobic soils follOWingthe fire served as the basis for a predicted hillside response-the -firef 1 0 0 d ~ sequence. However. the practiceof using the water drop test to determine the hydrophobic nature 01 thesoil yields information about infiltrationand water repellency at test points only.Several points at each site must betested to acquire useful information.The test also does not reflect the trueflow paths or the runoff processmechanisms for an area larger thana water drop, Hydrophobicity in theOakland Hills was spatially discontinu-

In partially urbanized watersheds likethose in the Oakland Hills. acceleratederosion due to fire may be dominated by

(61.560 m ') 01 sediment has beenremoved from the lake. yet the volumeof the lake in 1979 was still only 20percent 01 its 1907 volume (Mahoneyand others. 1979). Using the sedimentation of Lake TemescaJ. we determinederosion due to urbanization within the2.4-square-mile (6.2-km2j watershed tobe at a rate of 0.028 inch (0.7 mm) peryear lo r the last 72 years.

of the dirt road network. and sloughingalong the cut and fill embankments.Interestingly. no erosion conlrol measures were applied to the road networkduring either winter following the lire.even though dirt roads are known to bemajor contributors of sediment.

Using the total volume of storedsediments and drainage area. we canestimate an equivalent hillside surfaceerosion rate for the NOse watershedof between 0.024 and 0.028 inch(0.6 mm to 0 .7 mm) per year. valuesthat reflect the impacts of urbanization(Table 4).Elfects of Urbanlzallonand Rebuilding

Although one of the concerns following the fire was protection 01 downstream water bodies. the pre-fire effectsof urbanization on sediment productionin the Oakland Hills has been great.Concentrated road runoff has causedsignificant gullying of hillsides andscouring 01 the channel network. leaving little sediment in storage. and delivering much sediment to downstreamwater bodies such as Lake Temescaland San Francisco Bay (Mahoney andothers. 1979). Lake Temescal. thereceiving water body for approximately50 percent of the bum area. wasdredged three times between 1963 and1979. A total of 80.520 cubic yards

CALIFORNIA GEOLOGY N O V E M B E ~ D E C E M B E R 1 ~ "9


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Between October1991 and July 1993.building permits for1.094 homeswere approved(39 percent ofthe losthomes) and1.540 homeown-ers contacted Ihe Cityof Oakland about rebuilding (55 percentof the lost homes). Unfortunately. noneof the erosion control measures appliedto the firestorm area were deSigned tomitigate erosion caused by reconstruction activities. A year after the fire. LakeTemescal is experiencing increasedsedimentation and a decrease in waterquality (Freestone. 1993) as a result 01construction and the deteriorallon oftemporary straw bale sediment-monitoring structures in channels and gullies(which allowed the stored sediment tobe flushed into Lake Temescal and SanFrancisco Bay).

reduce overall establishment of vegetation. The germination of seeds in thesehydromu1ched areas did not occur unlilafter heavy rains in March. 1992.when the winter was essentiallyover (Photo 8).

......

hydromulching was completed. indicates that slopestreated with the hydromulchhad much lower vegetationdensities than untreatedslopes During the winter.germination of seeds withinthe hydromulch did not occurin many cases unlilthe hydromulch wasdisturbed by animals. leaving islands ofgreen in an otherwise gray landscape.Burgess Kay (1976) at the Universityof California Agricultural ExperimentStation at Davis has noted that acryliccopolymers of the type used in thehydromulch application follOwing theOakland lire often delay and reducetotal germination of seros. and may

Figure 5. Observed slope response. wherevertical now paths predominate.

ous. Areas that were typed as highlywater repellent did not generate thepredicted response because of the predominance of flow paths into thedeeper soil horizons (Figure 5).There is no record of how the estimated soil loss of 75 cubic yards peracre (142 m'/hectare) (unpublished

Interagency Task Force soil erosiontreatment meeting notes. October 24.1991) following the Oakland fire wasderived. but it is thought that the SCSused the Universal Soil Loss Equation(USLE). In the development of theUSLE. much of the work characterizingstorm erosion and raindrop impact onsoil detachment was performed on disturbed soils. namely agriculture andrangeland (Goldman and others. 1986).Such soils have been affected by activities that weaken and break up soil structure and particle cohesion. In fact. it isgenerally considered appropriate toapply the USLE to construction sites toestimate soil loss due to erosion However. the undisturbed urban wildlandsoils of the types found in the OaklandHills should not be considered highlyerosive. especially when subjected onlyto low intensity storms.

A comparison of aerial photographstaken on March 12. 1992 with thosetaken in De


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Photo 9. In March 1992, after an average rainfall season, 63 percent of all straw balecheck dams In the North Oakland Sports Center watershed had failed.

Standard erosion control manualsstate explicitly that straw bale checkdams should not be placed in areas thatreceive more than 1 cubic foot per second (1.7 ml/minute) flow; that the damshave a useful life of about 3 months:and that if they fail there is frequentlymore damage than if no barrier hadbeen installed (Goldman and others.1986) These assenions were reconfirmed in the Oakland fire area. Thestraw bale check dam data suggests thatsediment storage is less than 50 percenfeffective for average winter rainfall conditions. and much less effective for theextreme rainfall event for which planners were preparing (Photo 9). Addi-tionally. much of the sediment caughtbehind the dams may have come fromkeying or benching the bales into gullywalls. Because many gullies are at least10 feet (3 m) deep. the sediment thatwas excavated to install the bales wasnot removed from the active channel.Sediment was thereby provided to thenext downstream dam.

RECOMMENDATIONSOur analysis suggests that. even ifheavy winter rains had arrived. therewould not have been a higher landslidepotential on burned lands. and erosion

by overland flow would have been minimal. Contradictions between expectations and observations suggest thefollowing:1) Geology. topography. geomorphology. climate. and historical records

can be analyzed in advance to predictwhether the - f i r e - f l o o d ~ sequenceapplies. Landscape response is sitespecific: processes that occur in thesteep mountains of southern Californiaas a result of fire are not necessarilythe processes that will occur in otherlandscapes2) The water drop test is useful intesting for local hydrophobicity. hut itmay not be a reliable method for estimating potential runoff or subsequenterosion. Improved field testing. perhaps

involving a simple portable sprinkler.is needed.3) Sediment flux is largely a functionof availability and transport. The SCSsoil erosion index and the USLE appearin this case to overestimate the erosionpotential for undiSlurbed wildland soils.Application of these empirical procedures for estimating soil erosion involvesconsiderable uncertainties when theyhave not been calibrated with local

quantitative field measurements, Methods that do not rely on uncalibrated soilerosion indexes for estimating soil erosion for undisturbed wildland soilsshould be considered.4) Reseeding burn areas and theheavy application of hydromulch

appear to be inappropriate responseson burned slopes not having severeground disturbance. The most appropriate response after a similar urban/wildland burn may be to do nothing. How-ever. intense public pressure to -actmay not permit this response. evenwhen it is correct.5) On-site erosion and sedimentcontrol measures that increase infiltration and subsequently soil moistureshould not be used on slopes thaI havea high probability of landslide failure.6) Ground disturbance by fire suppression and post-fire reconstructionactivity may be the primary source ofaccelerated erosion. Perhaps the erosion control effon should be focused onthese specific areas rather than on thewholesale effects of the bum.7) The receiving water bodies in theOakland fire area (Lake Temescal andSan Francisco Bay) are sediment sinks:

all available sediment will find its wayinto the sinks. and will remain thereuntil removed. Money spent on hun-dreds of temporary straw bale structuresthaI decayed and then released theirstored sediments did not prevent sedimentation In these water bodies. Thisremedial measure was not cost-effective. A better solution would be longterm sediment retention basins at roadcrossings that can and should be easilycleaned. or permanent measures thatInvolve preventing gully erosion.8) In many environments. panicularly at the urban/wikiland interface.shallow landsliding may constitute themost significant hazard. and slope stability mayor may not be affected byfire, Maps developed by the City ofOakland even without hillside exposureby fire. as pan of a land-use management plan. should identify landslidefeatures and hazards. This informationin conjunction with the use of systemssuch as the USGS real-time storm

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BIOGRAPHIES

Bill Dietrich is a professor in the Department of Geology and Geophysicsat the University of Califomia at Berkeley. He r ~ e i v e d his Master's and PhD.degrees at the University of Washington. Bill is a geomorphologist who hasworked on hillside and fluvial processes around the wor ld

l aure l Collins received her undergraduate degree in geologyat the University of California at Berkeley where she is now a researcher inthe Department of Geology and Geophysics. At the t ime of the fi re. Laurelwas the geologist for the East Bay Regional Parks. pans of which were in thefire area.

Fred Booker received his undergraduate degree in geology at HumboldtState University. He is currently a graduate student in geology at the University of California at Berkeley. His Master's thesis evolved follOWing the lossof his home in the Oakland fire. Fred's thesis addresses the impacts of theOakland fire on hillside erosion and hydrology.

Cannon. S.H .. and Ellen. S.D.. 1988, Rainfal1that resulted in abundant debris-flowactivity dUflrlg the storm. In Stephen D.Ellen, and Gerald F. Wieczorek, editOIS.Landslides, floods. and marine ellectsof the storm of January 3-5. 1982, mthe San Francisco Bay regIOn; U.S.Geological Survey Professional Paper1434, p. 17-27.

Conard, S.G., Regelbrugge. J.C.. and Wills.R.D., 1991, Prelimmary ellects 01 ryegrass seeding on postfire establishmentof natural vegetatIOn in two Calilornlaecosystems; A paper presented at thet 1th conference on lire and forestmeteorology, April 16-19, 1991,Missoula. Montana.Conrad, C.E.. 1979. Emergency post-fireseedmg USing annual grass: CaillornlaDepartment 01 Forestry, ChaparralResearch and Development ProgramNewsletter (CHAPS). p. 58.DeBano. l. F .. 1968. Observations on waterrepellent soils In the western U.S.,

In Leonard DeBano. and John Letey.editors: Symposium in Water RepellentSolts, Proceedmgs. UnIverSity of California, Riverside, p. 17-30.DeBano. l. F.. 1981. Water repellent SOils.a state-ol-the-art: U.S. Departmentot Agriculture, Forest Service. PacilicSouthwest Forest and Range Experl'ment StatIon, Berkeley, Califorma,General Technical Reporl PSW46.21 p.Dunne. T .. Dietrich, W.E., and Brunengo.M.J .. 1980. SImple. portable eqUipmentfor erosion experiments under artiticlalramfall: Journal 01 Agricultural Englneenng Research, v. 25, p. 161-168.East Bay Regional Park District. 1981,Assessment of Impact ot development

01 vacant tand in the Temescal watershed, OCtober 15, 198 t. 7 PFlorsheim. J.L.. Kelter, EA. and Best.D.W., t991. Fluvlat sediment transportin response to moderate storm flowsfollOWing chaparral wlldhre. VenturaCounty. southern Califorma: GeologicalSociety of America Bulletm, v t03. p.504-511-Freestone, J.. 1993, Construction runolfpolluting Lake Temescal: PhoemxJournal. Oakland. Califorma, v. 2. no 9.May3.p.l .Gauller, C.R .. 1983. SedimentatIOn mburned chaparral watersheds: Is emergency revegetatIon lustlhed?: WaterResources Bulletm. v. 19, no. 5,p.793-802.Goldman, S.J., Jackson, K.. andBurszlynsky. T.A.. 1986. Erosion andsediment control handbook: McGrawHIli, San FranCISCo. California. 360 p

Florsheim. Ron Taskey. BlytheMickelson. Suzanne Anderson. andNelson Fernandes for their insightfulcomments and thoughtful review of thismanuscript.

REFERENCESAflderson. H.W .. Coleman. G.B.. andZinke. PJ .. 1959. Summer slides andwinter scour....dry-wet erosion In southern California mountains: U.S. Department 01 Agriculture, Forest Service,Pacllic Southwest Forest and RangeExpenment StallOn. Berkeley. Calilornla, General TechnIcal Report PSW-18.12 p.Barro. S.C., afld Conard, S.G., 1987. Useof ryegrass seeding as an emergencyrevegetation measure in chaparralecosystems: U.S. Department ot Agriculture. Forest Service, Paclhc Southwest Forest and Range ExperimentStatIOn. Berkeley. Callforrlla. GeneratTechmcal Report PSW-102. t2 p.Batro, S.C., and Conard. S.G .. 1991, Fireeffects on California chaparral systems:an overview: Envlronmentallnternatlonal. v. 17, P 135-149.Blrk, R.D. Wagoner, Ora. and Green.Pattlck. t979, Ralrttalt Simulators: U.S.Department 01 the Intenor. Bureau otLand Management Techmcat Note 326.51 p.Booker. FA. Pess. George. and Dietrich,W,E., 1992. Runort and erOSIOn in the

Oakland Hills. follOWing the hrestormot OCtober 20. 1991!abstract): EOS.Transactions o f the American GeophySIcal Union. v 73. no. 43, p. 202.

ACKNOWLEDGMENTS

Special thanks to PeterWohlgemuth. Tom Spittler. Joan

This research was funded in part byNSF Grant BCS-9207383. Our thanksto Chris Johnston. George Pess. andBob Potter for all their help and ideasduring the last year and a hal f. BethGier and Jordan Destabler for their laband winter field work. and to our fulltime summer field crew of StephanieHoeft and Nghia Le for their diligenceand above all their attention to detail.Thanks also to Suzanne Anderson.Nelson Fernandes. Darryl Granger. IanProsser. Juan Somoano. and RaymondTones who braved the poison oak andthe long days to help set up and conduct the summer and fall rainfall simulations.

warning system (Keefer and others.1987). could be used to predict debrisflow occurrence and pathways.

9) Erosion control efforts should bemotivated by the value of downsloperesources. and evaluated in the contextof the predominant processes that arepotentially detrimental to that resource.[n following this approach. agenciesneed to reassess how money is allocated for erosion control following fires.Money spent on temporary and limiteduse erosion control efforts is not necessarily cost-effective.

", CALIFORNIA GEOLOGY NOVEMB.R.OECEMBER 1993


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Howard. R.B. 1982, Erosion and sedImentation as part of the nalural system:U.S. Department of Agnculture. ForestservICe. Pacllic Southwest Forest andRange Experiment Slallon, Berkeley.California. Research NOle psw-sa.p.403-408.

Imason. A C .. VerSltalen, J M. vanMulltgan. EJ. and Sevlnk. J" 1992.The effects altire and water repellencyon In'lltrallon and runotl under MedIterranean forest: Catena, v 19:3.4 .p.345-362.

International ErOSIOn Control ASSOCIallon,1992. An uphill battle to save the soil:W,nter Bollelln. v 23'4. P 9-27.Kay. B l. 1976, Hydroseeding, straw,and chemlCaJs'lor eroslOfI control:

UC California at DaVIS AgnculturaJExpenment SlaMn Agronomy Progress Report no 77. June 1976. 14 p.Keeler. D.A . Harp. E.l.. and latkm. RS ..1986. FormatIon 01 ntis by debns flows

on burned. chaparral-coyered slopesIn the San FranciSCO Bay regIon.Cahlorma Geologteal Sooety ofAmerICa Abstracts with Programs.November 10-13, 1986,

Keefer. D.A .. Wilson. AC .. Mark. AK ..Brabb. E.E" Brown III , W.M.. Ellen,S.D.. Harp. E.l.. Wieczorek, G.F .. Alger,CS" and Zatkln. AS" 1987. Real-tImelandslide warning dUring heavy rainfall:Science, v. 238, p. 921-925.

Krammes. J.S.. 1965, Seasonal debrismovement from steep mountainsideslopes in southern California. In Proceedings of the Federal Inter-AgencySedimentation Conference. Jackson,MISSissippi. 1963: U,S. Department ofAgriculture Miscellaneous Publication.v. 970, p. 85-88.

Krammes, J.S" and HIli. L.W.. 1963. "Firstaid- for burned watersheds: U.S. Department of Agnculture. Forest Service,Pacllic Southwest Forest and RangeExperiment Station, Berkeley. Cahlorma.Research Note PSW-29. 7 P

Libby, W.J., and Rodrigues, K.A., 1992.Revegelatlng the 1991 OaklandBerkeley hillS burn; Fremontla. v. 20.no. 1. p. 12-18

Mahoney. Don, Rada, EA. and Roby. K.B..1979, Lake Temescal, pollutJon identif icat ion and source control program-acase study In urban runoH and erOSIoncontroL East Bay RegIonal Park DlstrlCl.Oakland, CaMornla, August 1979. P 23.McPtJee. JA , 1989. The control 01 nature:

Fanar, Slraus and GlrOlJx. New yort


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4 _ ~ ~ Y LANDSLID


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EVALUATIONFollowing the Tunnel Fire

October 19-23, 1991Oakland and Berkeley, California


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Photo 2. Hiller Highland area of Oakland. Calilornla.

Photo 3. Pallial burning 01 trees and shrubs indicates moderate fire intenSities.

Remoual of woody structural sup'port from stream channels or ripar'ian uegelatfon where sediment isstored in or adjacenl to the channels.Riparian vegetation was substantiallydamaged in the watersheds immediately upstream from the site 01 theParkwood Apartments and aboveRuthland Road (map; Photo 5). Sediment stored in these channels couldhave mobilized as stream channelderived debris flows. also called debristorrents. The volume of sediment inthe channel above the ParKwoodApartment site was estimated to be

(Photo 4). These field tests suggestedthat hydrophobiC development wasdiscontinuous. This discontinuity isconsistent with a low intensity burn.Up to 2 inches (5 cm) of rain lell in thearea 5 days after the fire was declaredunder control. Field work during andafter the rain revealed that only one ofthe areas identified as having a highburn intensity. the Claremont Creekwatershed. experienced rill erosionassociated with a continuous hydropho-bic soil layer (see map). The rilling andmicro debris flows were caused by run-off from fire suppression activitles andoccurred prior to Ihe storm (FredBooker. U.c. Berkeley. oral communi-cation. 1993).

Development of a continuouslayer of walerrepellenl soil. Initialfield assessment during the first weekfollOWing the fire included testing manyin-situ soil samples for hydrophobicity

these slopes and deposited in streamchannels were small.

Concentrations of dry ravel fromSleep slopes In stream channels. Onlya few dry ravel sites were observed inthe Tunnel Fire area (see map). Thevolumes of sediment transported from

Tunnel Fire area. The special studieszone lor the active Hayward Faulthas been legally defined by the StateGeologist under the provisions 01the Alquist-Priolo Special StudiesZones Act (Division of Mines andGeology. 1982).TUNNEL FIRE AREA SITE

CONDITIONSDMG investigated the followinggeomorphic and geologic factors thatcontribute to p o s t ~ f i r e channeJ-deriveddebris flows. Observations made byfield mapping (see map) and aerial photograph interpretation of the TunnelFire area are:Long regular slopes inclined moresteeply than 65 percent that arecleared of lIegelation. Although thereare several places in the Tunnel Fire

area where slopes exceed 65 percent.these slopes are not long and continuous, Steep slopes are broken bybenches along bedding planes and byold landslide benches. roads. driveways.and house pads.

'" CALIFORNIA GEOlOGY NOVEMBER DECEMBER 1993


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Areas with apparent high temperalUfeDry ravelAreas with observed hydfophobocsoil and rill erosiOnStream chanrlel wth npananvegetation damageGully (lxsexlstlllg) ...

Figure 2. Map ollhe Oakland Tunnel Fire area showlI lg areas of high burn IntenSllles, dry ravel, hydrophobic 50115. nparian damage. andpre-ellis\lng gullies. TopographIC map base by U.S. Geological Survey

CALIFORNIA GEOLOGY NOVEMBER DECEMBER t993 m


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Photo 4. Field testing for hydrophobic soils. Photo by Michael W. Manson.

Photo 5. Stored sediment along stream channel that couldmobilize. Rulhland Road watershed.

Recent Geologic Historyof Alluvial Fans

less than the storage capacity of a basinabove the site. The sediment stored inthe Ruthland area was substantiallygreater than the carrying capacity ofthe culvert beneath Ruthland Road thaIdrains the area. Had sediment mobilizedthere, it would have plugged the culvertand flowed down Ruthland Road,Because the houses that survived thefire are well above the road. mobilizedsediment would have been more of anuisance than a hazard. The unsupported stream channel sediments wereremoved by the City of Oakland following the fire.

Even though the immediate dangers of the Tunnel Firehave passed. the ever-present hazard of debris flows mustnot be forgotten. As woody vegetation is replaced by grassesthat were seeded-in during the emergency revegetation. thestrong. deep root systems may die. In addition. the grasseswill enhance the ability of rain to infiltrate. These processesmay increase the hazard of hillside-derived debriS flows.Removal of eucalyptus and Monterey pine trees in the firearea. as well as in other portions of the Oakland and Berkeleyhills may also increase landslide hazards unless suitable. deeprooted. woody vegetation is planted to hold the soil. Analysisof the Tunnel fire burn area by Springer and others (1992)suggests that 34 percent of 184 identified areas with geomorphology indicative of potential slope failure have a high risk.

SUMMARY AND CONCLUSIONS

The degree of development of soilon the alluvial fans gives information onthe hazard of debris flow activity. Southern California fans are steeply inclined.contain coarse boulders. and havepoorly developed soil. The undividedQuaternary deposits below the Oaklandand Berkeley hills are f1aHying. and 95 to 100 percent of thedeep loam to clay loam soils pass through a No.4 sieve (lessthan 3/16 of an inch 14.8 mml in diameter) (Welch. 1981).These observations take into account the horizontal offset ofthe fans along the Hayward Fault.

No areas were observed where the effects of the TunnelFire posed an immediate hazard to life or property from postfire debris flows. The potential for mobilization of sediment inthe watershed above Ruthland Road was reduced by the removal of the material following the fire. Other than in this onearea. emergency erosion control activities in the fire area maynot have been necessary. Because of the number of peopleand structures affected by the Tunnel Fire. emergency revegetation and mulching activities may have provided additionalprotection (Libby and Rodrigues. 1992). However. not everyone agrees that post-fire revegetation is appropriate (Gautier.1983: Taskey and others. 1989).

,,J,

,

"e CALIFORNIA GEOLOGY NOVEMBER DECEMBER 1993


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[ DMG SPECIAL PUBICATION 113 RELEASE]

ACKNOWLEDGMENTSDrafts of this paper were reviewedby Bradley E. Valentine (CDF) and

Michael W. Manson (DMG). Robert H.Sydnor (DMG) compiled the information on the geology of the Tunnel f irearea. The author wishes to thankStephen D. Ellen of the U.S. GeologicalSurvey (U.S.G.S.) for providing a draftof his work on hillside materials in thefire area.

Discussions of the effects of theTunnel Fire with Frederick A. Booker(U.c. Berkeley). William E. Deitrich(U.c. Berkeley). Laurel M. Collins (EastBay Regional Parks District). StephenD. Ellen (U.S.G.5.) and Raymond Wilson (U.5.G.5.) were helpful and informative.

REFERENCESDivision of Mines and Geology. 1982.Oakland East Quadrangle SpecialStudies Zones: AlqUist-Priolo FaultEvaluation Program. Revised OfficialMap (scale 1:24,000).Gautier, C.A., 1983. Sedimentation inburned chaparral watersheds: Is emergency revegetation justified?: WaterResources Bulletin, v, 19. no. 5,p.793-802.Libby, W.J .. and Rodrigues. K.A .. 1992,Revegetating the 1991 OaklandBerke

ley hills burn: Fremontia. v. 20. no. 1.p.12-18.Radbruch. D.H .. 1969. Aerial and engineerIng geology of the Oakland East quadrangle. California: U.S. GeologicalSurvey Geologic Quadrangle Map ofthe United States. Map GQ-769 (scale1:24.000).Smith. T.C.. 1980. Hayward Fault, Oaklandsegment: Division of Mines and Geology Fault Evaluation Report FER102.30 p.. 5 plates.Springer. James; Kulkarni, Ram; Huntsman. SCOll: and Frltas. Mark. 1992,Assessment of landslide risks after the

OCtober. 1991 firestorm. Oakland, California: Proceedings of the 35th AnnualMeeting of the ASSOCiation of Engineering Geologists. p. 188193.Stelnbrugge, K.V., Bennen, J.H .. Lagono,H.J .. DaVIS. J.F.. Borchardt. Glenn.and Toppozada. T.A., 1987. Earthquake planning scenano for a magnitude 7.5 earthquake on the HaywardFault In the San Francisco Bay Area:DIVIsion ot Mines and Geology SpecialPublication 78. 243 p.

Taskey, A.D., Curtis. C.L.. and Stone, J..1989, Wildfire, ryegrass seeding,and watershed rehabilitation: U.S.Department of Agriculture, ForestService. Pacihc Southwest Forest andRange Experiment Station, Berkeley,California, General Technical ReportPSW-109. p. 115-124.

PROCEEDINGS OF THE SECONDCONFERENCE ON EARTHQUAKEHAZARDS IN THE EASTERN SANFRANCISCO BAY AREA, SpecialPublication 113. Chief Editor. GlennBorchardt. 1992. $22.00.

The papers in this volume werepresented at the Second Conferenceon Earthquake Hazards in the EasternSan Francisco Bay Area on March25-29. 1992. at California StateUniversity. Hayward. More than 400earth scientists, engineers. and planners attended.

The proceedings of the first conference (DMG Special Publication62. available at a reduced price of$11.00) served as a focal point formuch of the earthquake hazard research conducted in the last decade.SP113 should serve a similar functionleading to the saving of lives and themitigation of hazards and structuraldamage. As reOected in this volume.two recent and significant events haveincreased awareness and rejuvenatedresearch in earthquakes in the EastBay: the 1988 earthquake forecastsby the Working Group on CaliforniaEarthquake Probabilities and the 1989Lorna Prieta earthquake.

SP 113 contains 72 papers and 16abstracts. most of which are summaries of more detailed technical worksmentioned in the references. Many ofthe questions asked at the first conference are answered in this volume;many are not. Among the reviews andupdates at this conference are: Estimates of the Holocene slip ratesof the Hayward. Rodgers Creek.and northern Calaveras faults (allabout 83 mm/yr). In 1982. thesedata were nonexistent. Guessesranged f rom 3 to 20 mm/yr.

Welch. L.E .. 1981, Soil survey of AlamedaCounty. California. western part:U.S. Department of Agriculture. SoilConservation Service. 103 pWorking Group on Califorma EarthquakeProbabilities, 1990. Probabilities 01large earthquakes occurnng In the San

Francisco Bay region. Califorma: U,S,Geological Survey Circular 1053. 51 p.

Estimates of future probabilities formajor earthquakes on the northernHayward. southern Hayward. andRodgers Creek faults (all about 0.25.or one chance in four. over the next30 years). In 1982. probabilityestimates were not possible. partly because the Holocene slip rate data werenot available.

Vast improvement in the measurement precision of creep rates. strain.and geodesy along most East Bayfaults. In 1982. the Antioch Fault wasthought to be creeping. It is not

BASIX (Bay Area Seismic Renec-tionImaging eXperiment), In 1982. faultoffsets of young sediments on the SanFrancisco Bay floor were only suspected. Preliminary results presentedat the conference clearly show offsetsin the sediments near Pillsburg andbetween the Rodgers Creek andPinole faults

Progressive state and local programs toabate seismic hazards of unreinforcedmasonry buildings and public buildingson East Bay faults. In 1982 the publicidentification of seismically hazardousstructures was nearly unheard ofToday. it is becoming commonplace.SP113 and SP62 are available for

reference and purchase at all three DMGoffices. For mail order. see the Publications Request Form on page 183

Publlcallons and Information Office801 K Street. MS 14-33Sacramento. CA 958143532(916) 4455716Bay Area Regional Ollice185 Berry Street, SUite 3600San Francisco. CA 94107(415) 904-7707

Southern California Regional Office107 South Broadway, Room 1065lo s Angeles. CA 90012-4402(213) 6203560

CALIFORNIA GEOLOGY NOVEMBER,DECEMBER 1993'"


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1. Eruption o f C er ro Negro,an active stratovolcano inNicaragua. A stratovolcanoor composite volcano is builtof alternating layers of lavaand pyroclastic deposits.These deposits accumulatearound the central vent in acone-shaped pile. Thesemassive cones ar e fre-quently cut by manydikes and sills.Lava may flowfrom fissuresradiating fromthe central vent.whereas the multisized pyroclastic materials are ejectedfrom the main vent.

2. Steam an d o th e r vaporsrising f ro m la rg e volcanicblocks erupted from themain crater recently. Compare with the older. coolervolcanic blocks at the endsof the tracks or furrows thatrun down the slope of themain cone. These tracksor furrows were plowed bythe rolling blocks. Somehouse-size blocks now lieloosely at the bot tom of theslope.

3. The c r a te r o f a d o r m a n tp a r as i ti c v e n t occurs onthe side of the larger coneand is subsidiary to it. Th eparasitic and main craters

may have a common sourceof magma. The parasitic crater faces the viewer.

4. Erupting parasitic vent.possibly a smaller s t r a t o v o l ~cano in an earlier stage ofdevelopment than the maincone.

5. C o n ta c ts b e tw e en lavaflows that emanated fromthe parasitic vent (4). Theseflows ar e small enough to beeasily distinguished. Thelarger lava flows from CerroNegro (left and right foreground) coalesce making itdifficult to distinguish i n ( l i ~vidual flows.

6. L a rg e c lo ud o f pyroclasticdebris (ash or ejecta), steam,

and other vapors eruptedfrom Cerro Negro. Th elarger, heavier fragments fallback on the cone while thesmaller, lighter ash fragmentsar e carried great distancesbefore they settle.

7. A smaller cloud o fd a r k e r material indi-cates that a localized eruption hasjust occurred.

8. Cloud ofvapors from th e volcanois mostly steam and ash. butalso contains chlorine, fluo-rine. sulfur. and their acids.

9. S h ad ow c a st by th e as ha nd va por cloud fromth e volcano (6) carried byturbulent hot gasses andwinds. When the volcanicash settles. the pyroclasticdeposit that forms is calledan ash fall.

10. A d o r m an t volcanic coneis old enough to have developed a soil profile and luxurious vegetation on its slopes.Th e crater rim has a visiblebreach at (B) where lavapoured from the cone. Th elava flow turned at the baseof the cone an d formedlevees (L) at the sides of theflow.

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Cerro Negro, December 4, 1968. Cerro Negro erupled again in early 1972. Photo by R.L. Williams, courtesy of Of, Ian Campbell.

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California's Rocks, Minerals, and Decorative Ston( M A T E R I A L TRIBE OR REGION USE J"

AgateAgatized woodActinoliteAlabasterAmazonsloneAmethystAmphibolite schistBasaltic rocksBiotiteCalciteCarnelianChalcedonyChalcopyriteChertCinnabarChlorite schistChrysocollaChrysolile asbestosChrysopraseDolomiteFeldspar. whileFeldspar. pinkFlintFluoriteGalenaGamelGilsoniteGypsumGraniteGraphiteHaliteHematiteJasperLimoniteMagnesian micaMagnesiteMalachiteManganeseMoss agateMuscoviteObsidianOnyxOpalPorphyryPumicePyriteOuartz crystalsQuartz, roseQuartz, smokySandstoneSchist (micaceous)SteatiteSerpentineTourmalineTurquoislincblende (sphalerite)

Southern CaliforniaSan Diego and Imperial CountySan Francisco Bay regionCentral CaliforniaSanta Barbara Channel regionSacramento Valley regionUniversalSacramento Della regionSan Diego, Imperial CountySouthern CaliforniaUniversalSan Jose, New Almaden Mine. Death ValleySan Francisco Bay regionSan Bernardino CountySacramento Valley regionSouthern San Joaquin ValleyImperial County

Southern CaliforniaSanta Catalina Island, Owens ValleyImperial CountySanta Barbara CountySouthern CaliforniaUniversalSouthern California desertUniversalUniversalSouthern and central CaliforniaUniversalSanta Barbara, Sacramento Valley regionsPomo tribe of Lake CountySacramento Valley regionImperial and San Diego counties and Mono lakeSan Francisco and Drakes Bay areasUniversalSouthern CaliforniaSouthern CaliforniaUniversalCentral and southern CaliforniaSan Diego and Imperial countiesUniversalSouthern CaliforniaUniversalSan Francisco Bay regionMesa Grande, San Diego CountySan Bernardino, [nyo countiesSacramento Valley region

ArrowpointsArrowpointsCharm stones, ceremonialCharm stones, ceremonialBeadsCeremonial plummetsMetates and mortarsOrnamentsBeadsArrowpoints, scrapersArrowpoints, scrapersPaint pigmentCharm stonesUnknownCeremonialUnknownMortar

ArrowpointsCeremonial amulets, paintUnknownCeremonial (1)OrnamentsMortars and pestlesBody paintFoodPaint pigmentArrowpoints, scrapersPaint pigmentBowls and jarsMoney and decorationPaint pigmentPaint pigmentOrnamentsArrowpoints and chipped toolsArrowpointsSpeatpointsAbrasiveCeremonial, arrowpointsArrowpointsMetates, mortars, abrasiveArrow straightenersVessels, pipes, ornaments, arrowstraightenersCharm stonesOrnamentsOrnamentsCeremonial

'"CALIFORNIAGEOLOGY NOVEMeERiOECEMBER 1993


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A CHECK ORMONEY ORDER MUSTACCOMPANY THIS ORDER. All nonU.S. orders must be padWith an international money order or draft payable in U.S. dollars and made out to DIVISION OF MINESAND GEOLOGY Send order to: DIVISION OF MINES AND GEOLOGY, P. O. B o 2980. Sacramento,Cel,fornla 95812-2980.

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Eanhquake planning scenano for a ma\lnitude 8.3 eanhquake on theSan Andreas Fault in the San Francisco Bay Area. Caltfornla. t982.Proceedrngs conference on earthquake hazards rn the eaStern SanFranCISCO Bay Area. California. t982 .. ..Eanhquake planning scenano for a ma\lnitude 7.5 eanhquake on theHayward Fault rn the San Franc,sco Bay Area. Cahfomla. t987 ....Proceedings 01 the Second Conterence on Eanhquake HalardsIn the Eastern San FranciSCO Bay Area. t992. (NEW) .

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List of Available Publications ....

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RGM001A Geologic map of the Sacramento quadrangle (set of four sheets), t982 $t600RGM002A GeolO\llC map of the Santa Rosa quadrangle (sel ot five sheets)_ 1982 _._._ $1600RGM003A Geologic map of the San Bernardino quadrangle (set ot frve sheets). 1987 .. $16,00RGM004A Geolog,c map of the Weed quadrangle ( set of tour sheets). 1988 $16,00RGM005A Geologic map of the San FranciscoSan Jose quadrangle(set of !rve sheeIS). 1990 .. $18_00RGM007A GeologiC map ot the ChiCO quadrangle (set of five sheeIS)_ , 992 .. $22,00CALIFORNIA GEOLOGY

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SPECIAL REPORTSR153 Minerai Land Class,Ilcation: Aggregate Materials In the Western San DiegoCounty Proc!uction--Consumpllon legion 1982. Reprinted 1993 .

SPECIAL PUBLICATIONS

I - - - - - - - - - - - - - - - - - - - - - - - ~ - I DIVISION OF MINES AND GEOLOGYI Publications Request FonnIIIIIIIIIIIIIIIIIIIIIIII: NAME _I STREET ----------------------L CITY============

The Native Americans' conservationof natural resources is exempliliedby the Maidu flint miner at TableMountain, Bulle County. He wasprohibited from removing more flintIhan he could delach with one blowof a stone hammer.

Mines and quarries belonged not toIndividuals. but 10 the group thatlived in the area. VisItors usuallyhad 10 ask permissIon to use theresources, but were nol necessarilyrequired to pay lor them. Many minesites were neutral ground, placeswhere warring tribes were expectedto be peaceful.

Most Native American mining wasof outcrops. although there weresome large open-pi!and underground workings, Mined sub-Slances were altered by evaporalion. leaching, and oxidization. Forinstance. al Akwurawawa ("redplace") in Imperial County. theCocopa made a bright red pigmentby burning dull reddish hematiteood ,oak;,. it ;, wateno ,ott"". - ,1 ' ~ . . ; .and leach oUllhe salt. .....,."1:"" ,- .

,., . ~ , . -- - - - - ~ ~ " " - " ' S : .".. > ~ ~ " ' ~ ,f _ ~ _ r : .. '"Native Amencans used asphalt . ,for caulkmg plank canoes. wa te r_ " f i r I -' I : -/' !: l 'proofing baskets, mending, and - .joining 1001 components. Clays w &used to make pottery and bake : 'fballs when rocks were unavaifablfor Slone boiling (heating liquidswith hoI rocks). Acorn meal wasmixed with a red clay and baked.The iron oxide In the clay convertedthe tannic acid in the acorn meal toan insoluble compound. Salt wasmIned for food, slate was made intopendants, picks, and chisels, andchalk was used as paint.

Information on these pages is fromMines and Quarries of the Indiansof California by Robert F. Heizerand Adam E. Treganza. published In1944 by the Division of Mines in theCalifornia Journal of Mines and Geology. v. 40. no. L p. 291-359.T ~ b l e modified from &11. 5 H . 1941. TheMining of Gems and Ornamenlal Sranesby ArnerlCCln IndlClns, Bureau of AmericanEthnology. Bulletin 128. AnthropologicalPaper 13.

by Native Americans

CALIFORNIA GEOLOGY NOVEMBER/DECEMBER t993 '"


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CONFERENCE NOTESSecond Thematic Conference,

Remote Sensing fo r Marineand Coastal Environments

New Orleans. LouisianaJanuary 31-February 2.1994ERIM/Marine Environment Conference1r (313) 994-1200. extension 3234

ISOPE94/PACOMS94Osaka/Kobe. JapanApr il 10-15 . 1994Professor Chung

1I ' (303) 2733673

PACON 94Townsville. AustraliaJuly 4-8 . 1994

1I ' 61 77 814817FAX: 61 77 755429INSMAP '9 4

Hannover. GennanySeptember 19-23. 1994

1I' (703) 2859235SOSC - 94 IPACOM5-94)Beijing. China

April 17-18. 1994Professor Chung

1I' (303) 273-3673

Underwater Intervention 1994San Diego. CaliforniaFebruary 710.1994UI '94 Committee1I' (619)4228918

FAX: (619) 4264421lOA Core Group an d Oceanology

International 94 Exhibitionand Conference

Brighton. United KingdomMarch 8-11.1994

Bob Munlon1I' 4481 5495831FAX: 4481 541 5657

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ADDRESS CHANGE: Send a recent address label and your new address.Allow 60 days to reflect address change.D IIA CHECK OR MONEY ORDER MUST ACCOMPANY THIS ORDER. All nonUS orda's must ba IpaJd With an Internat,onal money order or draft payabla In US dOllars and mada out to DIVISION OF IMINES AND GEOLOGY Sand all orders andlo, address change 10:

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'" CALIFORNIA GEOLOGY NOVEMBER DECEMBER 1993


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GlaciationTHE LAST INTERGLACIAL-GLACIALTRANSITION IN NORTH AMERICA.Edited by Peter U. Clark and PeterD. Lea. 1992. Special Paper 270.Geological Society of America. Inc.,P.O. Box 9140. Boulder. CO 80301.18001472-1988.317 p. $62.50.soft cover.

An outgrowth of the 1988 symposium. Last Interglaciation/GlaciationTransition (122-64 ka) in NorthAmerica. this volume focuses on theresponse of North American ice sheetsand glaciers to climate change followingthe last period between glaciations. Toevaluate and describe this response. 21articles offer geographically significantcoverage providing a continental perspective of former North American icesheets and glaciers_Geologic HazardsTHE CITIZENS' GUIDE TO GEOLOGIC HAZARDS. By Edward B.Nuhfer. Richard J. Proctor. and PaulH. Moser. 1993. The American Institute of Professional Geologists. 7828Vance Drive. Suite 103. Arvada. CO80003-2125. (303) 431-0831. 134 p.$19.95. soft cover.

This book is for non-scientists whowould like to learn more about the geologic hazards they hear about from dayto day. We know when there is a natural disaster. but what about exposureto radon or asbestos? What is aciddrainage and how does it affect us?This is a guide for planners. contractors. home-owners. officials. insuranceunderwriters. lenders and financiers.realtors. sdence teachers. and students.Informed citizens are less likely to purchase unsuitable land and less likely tolose life or property to geologic hazards.

Hazards from reactive minerals.asbestos. and gases are covered as wellas those from geological processes suchas earthquakes. volcanoes. landslides.avalanches. subsidence. floods. tsunamis. storm surge. and coastal erosion.Sources of help from geologists andinsurance professionals are listed inappendices.AntarcticaGEOLOGY AND PALEONTOLOGYOF THE ELLSWORTH MOUNTAINS.WEST ANTARCTICA. Memoir 170.Edited by Gerald F. Webers. CampbellCraddock. and John F. Splettstoesser.1992. Geological Society of America,Jnc., P.O. Box 9140, Boulder. CO80301. (800) 472-1988. 459 p ..three plates. $97.50. hard cover.

The Ellsworth Mountains offer im-portant clues to the Phanerozoic historyof West Antarctica. Discovered in 1935by Lincoln Ellsworth. these rugged.angular peaks spark special interestbecause they are strategically locatedbetween the East Antarctic craton andthe tectonically active zone of coastalWest Antarctica. Memoir 170 contains23 articles. an appendix on mineralresources. and a bibliography.Field SafetyPLANNING FOR FIELD SAFETY. Bythe American Geological Institute. AGIPublications Center. P.O. Box 205.Annapolis Junction. MD 20701. (301)953-1744.197 p .. $14.95 plus $4.00shipping and handling. soft cover.

This hook describes hazards andpitfalls fieldworkers may encounter.suggests ways to avoid them. and tellswhat to do if they occur. The goal is tomake fieldworkers more conscious ofsafety. Topics include pretrip planning,equipment precautions. field safety.transportation. weather. animals andplants, regional hazards, and emergencies. Precautions for group leaders andshipping rock samples are also covered.These guidelines for wilderness safetywere compiled initially for students ofgeology; however. others including hik-ers, backpackers. and fieldworkers in

any profession will lind this informationuseful.GeothermalMONOGRAPH ON THE GEYSERSGEOTHERMAL FIELD. Special ReportNo. 17. Edited by Claudia Stone. 1992.Geothermal Resources Council. P.O.Box 1350. Davis. CA 95617-1350.(916) 758-2360. 327 p .. two plates.$28.50. hard cover.

Through 34 papers. 49 authorspresent a broad sampling of the latesttheory and technology concerninggeothermal development in the UnitedStates. They concentrate on TheGeysers. which is about 75 miles northof San Francisco and the world's largestdeveloped geothermal field.The Monograph papers are groupedinto two major categories: geothermalresources and geothermal technology.The resources section includes the his-torical setting. the geology and geothermal phenomena. and a description ofthe resetvoir. The technology sectiondescribes drilling. steam productionand fluid handling. electric power generation. and environmental issues. Twocase studies are included.

HistoryTHE DISCOVERY OF SAN FRAN-CISCO SAY; The Portola Expeditionof 1769-1770. By Miguel Costans6.1992. Great West Books. P.O. Box1028. Lafayette, CA 94549.(51012833184.215 p. $14.95(California addresses add $1.23 salestax), plus $2.00 shipping, soft cover.

On July 14, 1769 an expeditionled by Don Gaspar de Portola. Governor of the Peninsula of California (BajaCalifornia), started north from SanDiego in search of Vizcaino's MontereyBay. Portola's men were the first Europeans to explore by land what is nowCalifornia. They marched up the coastpast Los Angeles. Santa Barbara, andMonterey. to San Francisco and inlandto Hayward. This book is the diary ofEnsign Miguel Costans6. the expedition's engineer. Most of what Costans6

'"CALlFORNIA GEOLOGY NOVEMBER/DECEMBER 1993


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more prospects .. .

This book isa comprehensivelook at the gemological wealth of EastAfrica. a uniqueregion encompassing what may be theworld's richest gemdeposits. Kenyaand Tanzania aredescribed in theirlull mineralogicalsplendor lor lapidaries. gemologists.collectors. travelers.and anyone withan interest in theworld's gemstones.

Gems

Nearly all knownspecies of importantgems are found inEast Africa. Thegem fields aredescribed usingregional geologicmaps. detailed mapsof mine vicinities.cross sections. andphotographs. Eachgem variety is pho-tographed to show the striking colorand brilliance. The book's final chaptercovers over 20 less important gemsincluding amethyst. beryl. moonstone.

and peridot.

an extensive bibliography. There isalso an extensive map bibliography thatincludes entries back to 1603. as well asall U.S. Geological Survey quadranglesin the county.The entries themselves are interesting and sometimes humorous. Many

ar e followed by quotations from newspapers. magazines. or historical documents. All are highly readable capsulesof local history.

GEMSTONES OF EAST AFRICA.By Peter C. Keller. 1992, GeosciencePress. 12629 N. Tatum Boulevard..Suite 201. Phoenix. AZ 85032. (602)9532330. 144 p. $50.00. hard cover.

Each entry is explained in full.

Place Names

should be in the library of anyone interested in the development 01 this mostscenic and interesting part of California.

MONTEREY COUNTY PLACENAMES: A Geographical Dictionary.By Donald Thomas Clark. 1991.Kestrel Press. P.O. Box Q. Carmel Valley. CA 939240135. (408) 659-2807.737 p. $21.95. soft cover: $29.95.hard cover.This volume is an exhaustive refer

ence on the origin and history ofMonterey County names and. as such.

glimpses of the gold rush are found indescriptions of Rough and Ready, thePelton wheel, the long tom. LolaMontez. J.M. Studebaker. Coyoteville.Humbug City. the Clampers. the BigFour. Hangtown. and many others.

RhodOnite (pink) and manganite (black). Rhodonite is lound in the TrinltyKlamatharea and Sierra Nevada in California. Rhodonite with manganite is a semipreciousgem used chiefly for cabochons or polished slabs.

saw has been transformed beyond beliefand imagination. but from the discoverypoint in San Mateo County. you canstill see Point Reyes. the white cliffs ofDrakes Bay. and the magnificent sweepof San Francisco Bay.

Editor Peler Browning has done afine thing in re-issuing this most important historical account. It has a placein the library ofany student ofearly California.

The Spanish and English texts areprinted on facing pages. so they canbe easily compared. Information fromother historical manuscripts appears infootnotes. After the diary there is amodern account of how the route canbe [raced by car. This is followed by alist of campsites used during the 116days of the Portola expedition.

This is a bookfor anyone interested in the historyof the MotherLode. Armchairtravelers as wellas those on wheelswill enjoy followingthe highways andbackroads ofPlacer. EI Dorado. Sacramento.Nevada. Yuba. Sierra. and Plumascounties. Illustrations. maps. historicalphotos, diary excerpts. and descriptionsof points of interest are interspersed

THE GOLDENHILLS OF CAUFORNIA. VOLUMETWO: ADescriptive Guideto the Mother LodeCounties of theNorthern Mines.By Allan Masri.1983. WesternTanager Press.1111 PacificAvenue, SantaCruz. CA 95060.1408) 425-1111.131 p. $7.95. softcover.

caliifornia geology magazine nov-dec 1993

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