Phytoplankton blooms and nitrogen productivity in San Francisco Bay

San Francisco Bay has been considered an HNLC or HNLG (high nutrient low chlorophyll or low growth) region with nonlimiting concentrations of inorganic nutrients yet low standing stocks of phytoplankton. Most of the studies leading to this conclusion come from the South Bay and little is known about nutrient processes and phytoplankton productivity in the northern and central parts of the estuary. Data collected over 3 yr (1999–2003) in Suisun, San Pablo, and Central Bays describe the availability of dissolved inorganic nitrogen (DIN), silicate, and phosphate and the seasonal variability in phytoplankton abundance. Rate measurements of fractionated nitrogen productivity provide the relative contributions of different forms of DIN (ammonium and nitrate) and different sized phytoplankton to the development of seasonal phytoplankton blooms. Regional differences in bloom dynamics are observed with Suisun Bay, the least saline, highest nutrient, most turbid region having less phytoplankton biomass and productivity than San Pablo and Central Bays, except in the abnormally wet spring of 2000. Spring blooms in San Francisco Bay are driven primarily by high rates of nitrate uptake by larger phytoplankton cells following a period of increased ammonium uptake that depletes the ambient ammonium. The smaller occasional fall blooms are apparently flueled mostly by ammonium uptake by small sized phytoplankton. The data suggest that the HNLC condition in the northern and central parts of San Francisco Bay is due primarily to light availability modulated by the interaction between ammonium and nitrate, and the relative amounts of the two forms of the DIN pool available to the phytoplankton.     

Likely Population-Level Effects of Contaminants on a Resident Estuarine Fish Species: Comparing <Emphasis Type="Italic">Gillichthys mirabilis</Emphasis> Population Static Measurements and Vital Rates in San Francisco and Tomales Bays

Gillichthys mirabilis population static measurements (abundance, age, and size class structures) and vital rates (growth, mortality, recruitment) were monitored on an annual basis from 2002 to 2007. Population-level metrics were used to gauge habitat quality at two study sites (a contaminated site and a reference site) in two large northern California estuaries (San Francisco and Tomales Bays). San Francisco Bay populations exhibited slower growth and higher mortality rates and contained higher amounts of contaminants than Tomales Bay. Recruitment rates were highest at contaminated sites (Stege Marsh and Walker Creek) in 3 years out of 5 years, suggesting low adult survival. This study suggests that population-level effects on a residential fish may be attributed to estuarine contamination on the US Pacific coast.     

The effects of the San Francisco Bay plume on trace metal and nutrient distributions in the Gulf of the Farallones

The distributions of particulate elements (Al, P, Mn, Fe, Co, Cu, Zn, Cd, and Pb), dissolved trace metals (Mn, Fe, Co, Cu, Zn, and Cd), and dissolved nutrients (nitrate, phosphate, and silicic acid) were investigated in the Gulf of the Farallones, a region of high productivity that is driven by the dynamic mixing of the San Francisco Bay plume, upwelled waters, and California coastal surface waters. Particulate metals were separated into >10 and 0.4-10 μm size-fractions and further fractionated into leachable (operationally defined with a 25% acetic acid leach) and refractory particulate concentrations. Dissolved metals (< 0.4 μm pore-size filtrate) were separated into colloidal (0.03-0.4 μm) and soluble (<0.03 μm) fractions. The percent leachable particulate fractions ranged from 2% to 99% of the total particulate concentration for these metals with Mn and Cd being predominantly leachable and Fe and Al being predominantly refractory. The leachable particulate Pb concentration was associated primarily with suspended sediments from San Francisco Bay and was a tracer of the plume in coastal waters. The particulate trace metal data suggest that the leachable fraction was an available source of trace metal micronutrients to the primary productivity in coastal waters. The dissolved trace metals in the San Francisco Bay plume and freshly upwelled surface waters were similar in concentration, with the exception of Cu and Co, which exhibited relatively high concentrations in plume waters and served as tracers of this water mass. The dissolved data and estimates of the plume dynamics suggest that the impact of anthropogenic inputs of nutrients and trace metals in the San Francisco Bay plume contributes substantially to the concentrations found in the Gulf of the Farallones (10-50% of estimated upwelled flux values), but does not greatly disrupt the natural stoichiometric balance of trace metal and nutrient elements within coastal waters given the similarity in concentrations to sources in upwelled water. In all, the data from this study demonstrate that the flux of dissolved nutrients and bioactive trace metals from the San Francisco Bay plume contribute to the high and relatively constant phytoplankton biomass observed in the Gulf of the Farallones.     

Quaternary crustal deformation along a major branch of the San Andreas fault in central California

Deformed marine terraces and alluvial deposits record Quaternary crustal deformation along segments of a major, seismically active branch of the San Andreas fault which extends 190 km SSE roughly parallel to the California coastline from Bolinas Lagoon to the Point Sur area. Most of this complex fault zone lies offshore (mapped by others using acoustical techniques), but a 4-km segment (Seal Cove fault) near Half Moon Bay and a 26-km segment (San Gregorio fault) between San Gregorio and Point Ano Nuevo lie onshore.At Half Moon Bay, right-lateral slip and N—S horizontal compression are expressed by a broad, synclinal warp in the first (lowest: 125 ka?) and second marine terraces on the NE side of the Seal Cove fault. This structure plunges to the west at an oblique angle into the fault plane. Linear, joint0controlled stream courses draining the coastal uplands are deflected toward the topographic depression along the synclinal axis where they emerge from the hills to cross the lowest terrace. Streams crossing the downwarped part of this terrace adjacent to Half Moon Bay are depositing alluvial fans, whereas streams crossing the uplifted southern limb of the syncline southwest of the bay are deeply incised. Minimum crustal shortening across this syncline parallel to the fault is 0.7% over the past 125 ka, based on deformation of the shoreline angle of the first terrace.Between San Gregorio and Point Ano Nuevo the entire fault zone is 2.5–3.0 km wide and has three primary traces or zones of faulting consisting of numerous en-echelon and anastomozing secondary fault traces. Lateral discontinuities and variable deformation of well-preserved marine terrace sequences help define major structural blocks and document differential motions in this area and south to Santa Cruz. Vertical displacement occurs on all of the fault traces, but is small compared to horizontal displacement. Some blocks within the fault zone are intensely faulted and steeply tilted. One major block 0.8 km wide east of Point Ano Nuevo is downdropped as much as 20 m between two primary traces to form a graben presently filling with Holocene deposits. Where exposed in the sea cliff, these deposits are folded into a vertical attitude adjacent to the fault plane forming the south-west margin of the graben. Near Point Ano Nuevo sedimentary deposits and fault rubble beneath a secondary high-angle reverse fault record three and possibly six distinct offset events in the past 125 ka.The three primary fault traces offset in a right-lateral sense the shoreline angles of the two lowest terraces east of Point Ano Nuevo. The rates of displacement on the three traces are similar. The average rate of horizontal offset across the entire zone is between 0.63 and 1.30 cm/yr, based on an amino-acid age estimate of 125 ka for the first terrace, and a reasonable guess of 200–400 ka for the second terrace. Rates of this magnitude make up a significant part of the deficit between long-term relative plate motions (estimated by others to be about 6 cm/yr) and present displacement rates along other parts of the San Andreas fault system (about 3.2 cm/yr).Northwestward tilt and convergence of six marine terraces northeast of Ano Nuevo (southwest side of the fault zone) indicate continuous gentle warping associated with right-lateral displacement since early or middle Pleistocene time. Minimum local crustal shortening of this block parallel to the fault is 0.2% based on tilt of the highest terrace. Five major, evenly spaced terraces southeast of Ano Nuevo on the southwest flank of Mt. Ben Lomond (northeast side of the fault zone) rise to an elevation of 240 m, indicating relatively constant uplift (about 0.19 m/ka and southwestward tilt since Early or Middle Pleistocene time (Bradley and Griggs, 1976).     

Frequency of debris flows and rockfall along the Mendoza river valley (Central Andes), Argentina: Associated risk and future scenario

The frequency of debris flows and rockfalls was estimated by temporal distribution of these events during the last 50 years. This parameter was expressed by annual probability of occurrence and mean interval of recurrence of historical events. More recurrent events in this sector of the Central Andes are associated with the Guido locality and tunnels situated along International road No. 7. Furthermore, these events are more frequent in Cordillera Frontal where the mean recurrence interval was lower than in Precordillera. The maximum interval of recurrence is rarely greater than 20 years, showing the activity of these events on human lives and infrastructure in this region. The accuracy of the determined recurrence frequency is discussed. A future scenario indicates that landslides will be probably more frequent under global climate change. As a consequence, those most vulnerable elements in the region, the international access routes, may be severely damaged in the future, implying an adverse impact in our regional economy.     

Reassessing the tsunami risk in major ports and harbors of California I: San Diego

We assess tsunami hazards in San Diego Bay, California, using newly identified offshore tsunami sources and recently available high resolution bathymetric/topographic data. Using MOST (Titov and Synolakis, J Waterways Port Coastal Ocean Eng ASCE 124(4):57–171, 1998), we simulate locally, regionally and distant-generated tsunamis. Local tsunami source models use more realistic fault and landslide data than previous efforts. With the exception of the Alaska-Aleutian Trench, modeling results suggest that local sources are responsible for the largest waves within the San Diego Bay and Mission Bay. Because San Diego Bay is relatively well protected by North Island and the Silver Strand, the wave heights predicted are consistently smaller inside the harbor than outside. However, historical accounts, recent tsunamis and our predictions show that San Diego Bay is vulnerable to strong tsunami induced currents. More specifically, large currents are expected inside the harbor for various distant and local tsunami sources with estimated flow velocities exceeding 100 cm/s. Such currents have been damaging to harbor facilities, such as wharves and piers, and may cause boats to break from moorings and ram into adjacent harbor structures, as observed in recent historic tsunamis. More recently, following the M _w 8.8 February 27, 2010 Chile earthquake, tsunami-currents damaged docks/piers in Shelter Island confirming our findings. We note that the first generation of inundation maps in use in San Diego County by emergency management was based on much larger “worst case but realistic scenarios” (Synolakis et al. 2002a), which reflected the understanding of offshore hazards pervasive ten years ago. Large inundation and overland flow depths were observed primarily in local tsunami source simulations. In particular, locally induced tsunamis appear capable to overtop the Silver Strand. The results suggest that further work needs to be carried out with respect to local tsunami sources as they seem to have worse impact in the San Diego region than previously thought but probably low probability of occurrence. We also predict that a coastal community can be devastated simultaneously by large waves inundating shores and large currents in locations with small flow depths.     

Marine terrace deformation, san diego county, California

The NW—SE trending southern California coastline between the Palos Verdes Peninsula and San Diego roughly parallels the southern part and off-shore extension of the dominantly right-lateral, strike-slip, Newport—Inglewood fault zone. Emergent marine terraces between Newport Bay and San Diego record general uplift and gentle warping on the northeast side of the fault zone throughout Pleistocene time. Marine terraces on Soledad Mt. and Point Loma record local differential uplift (maximum 0.17 m/ka) during middle to late Pleistocene time on the southwest side of the fault (Rose Canyon fault) near San Diego.The broad Linda Vista Mesa (elev. 70–120 m) in the central part of coastal San Diego County, previously thought to be a single, relatively undeformed marine terrace of Plio—Pleistocene age, is a series of marine terraces and associated beach ridges most likely formed during sea-level highstands throughout Pleistocene time. The elevations of the terraces in this sequence gradually increase northwestward to the vicinity of San Onofre, indicating minor differential uplift along the central and northern San Diego coast during Pleistocene time. The highest, oldest terraces in the sequence are obliterated by erosional dissection to the northwest where uplift is greatest.Broad, closely spaced (vertically) terraces with extensive beach ridges were the dominant Pleistocene coastal landforms in central San Diego County where the coastal slope is less than 1% and uplift is lowest. The beach ridges die out to the northwest as the broad low terraces grade laterally into narrower, higher, and more widely spaced (vertically) terraces on the high bluffs above San Onofre where the coastal slope is 20–30% and uplift is greatest. At San Onofre the terraces slope progressively more steeply toward the ocean with increasing elevation, indicating continuous southwest tilt accompanying uplift from middle to late Pleistocene time. This southwest tilt is also recorded in the asymmetrical valleys of major local streams where strath terraces occur only on the northeast side of NW—SE-trending valley segments.The deformational pattern (progressively greater uplift to the northwest with slight southwest tilt) recorded in the marine and strath terraces of central and northern coastal San Diego County conforms well with the historic pattern derived by others from geodetic data. It is not known how much of the Santa Ana structural block (between the Newport—Inglewood and the Elsinore fault zones) is affected by this deformational pattern.     

Correlation of the Rockland ash bed,a 400,000-year-old stratigraphic marker in northern California and western Nevada,and implications for middle Pleistocene paleogeography of central California

Outcrops of an ash bed at several localities in northern California and western Nevada belong to a single air-fall ash layer, the informally named Rockland ash bed, dated at about 400,000 yr B.P. The informal Rockland pumice tuff breccia, a thick, coarse, compound tephra deposit southwest of Lassen Peak in northeastern California, is the near-source equivalent of the Rockland ash bed. Relations between initial thickness of the Rockland ash bed and distances to eruptive source suggest that the eruption was at least as great as that of the Mazama ash from Crater Lake, Oregon. Identification of the Rockland tephra allows temporal correlation of associated middle Pleistocene strata of diverse facies in separate depositional basins. Specifically, marine, littoral, estuarine, and fluvial strata of the Hookton and type Merced formations correlate with fluvial strata of the Santa Clara Formation and unnamed alluvium of Willits Valley and the Hollister area, in northwestern and west-central California, and with lacustrine beds of Mohawk Valley, fluvial deposits of the Red Bluff Formation of the eastern Sacramento Valley, and fluvial and glaciofluvial deposits of Fales Hot Spring, Carson City, and Washoe Valley areas in northeastern California and western Nevada. Stratigraphic relations of the Rockland ash bed and older tephra layers in the Great Valley and near San Francisco suggest that the southern Great Valley emerged above sea level about 2 my ago, that its southerly outlet to the ocean was closed sometime after about 2 my ago, and that drainage from the Great Valley to the ocean was established near the present, northerly outlet in the vicinity of San Francisco Bay about 0.6 my ago.     

Impact of high herbivore densities on introduced smooth cordgrass,Spartina alterniflora,invading San Francisco Bay,California

Spartina alterniflora, smooth cordgrass, invading San Francisco Bay, California (USA), is attacked by high densities of a plant hopper, Prokelisia marginata, and a mirid bug, Trigonotylus uhleri. Both herbivores are sap-feeders. We investigated the impact of these herbivores on S. alterniflora's growth rate, vegetative spread, and seed production by manipulating herbivore densities in the field and in a greenhouse. Herbivore densities in the field peaked in early fall, with P. marginata averaging more than 300 individuals per mature culm of S. alterniflora (about 100,000 per m²) and T. uhleri densities exceeding 10 per culm (about 3,000 per m²). Field reductions of herbivore densities by approximately 70% with insecticidal soap did not result in greater vegetative growth rates or lateral spread of plants; plants grew vigorously with the highest densities of insects. In the greenhouse study, conducted with seedlings, herbivory significantly reduced plant mass and tiller number in some but not all replicate herbivory treatments. In both field and greenhouse, there were significant differences between some clones' growth rates independent of herbivory. Inflorescence production in the field was not affected by reduced-herbivory treatments. Seed set was low under conditions of both natural and reduced herbivory, averaging 0.4%. Despite densities of P. marginata and T. uhleri that are much higher than typically observed in areas where S. alterniflora is native, herbivory by these particular insects appears to have little impact and in unlikely to limit S. alterniflora’s spread through San Francisco Bay. *** DIRECT SUPPORT *** A01BY070 00009     

地下共同沟的开发利用与立法

当该地人均GDP达到1000美元时就可以进行地下空间的开发利用。我国的很多城市人均GDP早已突破了1000美元,并且争相进行地铁、地下商场、地下综合体的开发。但是,共同沟的发展仍然很缓慢,这与共同沟自身的特点有关：共同沟自身建造成本问题、盈利问题等一系列问题制约了共同沟的发展。所以共同沟的发展需要政府的支持,需要法律的支持。本文通过对国内外共同沟的建造历史、共同沟的优缺点、政府及法律方面的分析。来阐述共同沟的建造及立法的重要性。     

Design and costs for a system to reduce chloride levels in the Red River by shallow-well collection and deep-well disposal

 The Red River drains 242000 km² with 90% of this area being downstream of discharges from naturally occurring brine seeps and springs. The upstream area has been designated as a major chloride emission area in Texas and Oklahoma. Ten major brine source emission areas along the tributaries to the Red River were identified by U.S. Public Health Service and U.S. Army Corps of Engineers. Eight of these areas were deemed suitable for the control of brine emissions by structural methods including a ring dike to enclose brine springs; low flow dams to capture and divert stream flows with high chloride content to evaporation lakes; and shallow aquifer brine collection wells with a deep-well disposal system. Two adjacent emission areas, designated as Areas XIII and XIV, contribute 500 metric tons of salt per day to the Red River. These areas, along Jonah Creek and Salt Creek, tributaries to the Prairie Dog Town Fork of the Red River were selected for investigation to control brine emission by utilization of shallow collection wells and disposal by deep injection wells. Drilling programs and pumping tests were performed to determine the number and location of shallow collection wells. Eighteen wells with 12 operating full time, will be located in the primary emission areas. The collected brine will be conveyed through corrosion-resistant pipelines to a treatment facility for filtration at a rate of 300 l/s. Additional pipelines will convey the filtered brine to deep injection wells for disposal. Nine deep wells will be installed with seven operating full time. Design criteria for the project are 100-year life expectancy and automated operation with minimum supervision and maintenance. The required minimum operating, maintenance and supervision coupled with 100-year life expectancy of the project added significantly to the estimated US $58 million capital cost of the project. However, the reduction in annual cost for labor, repairs and replacement of the component of the system should result in a lower life cycle cost. The estimated annual operating and maintenance cost is US $4.7 million. Received: 5 May 1998 · Accepted: 30 June 1998     

粤港澳大湾区水资源现状及其与社会经济协同演化趋势——与国际湾区对比研究

粤港澳大湾区（以下简称大湾区）水资源现状及其演化规律关系到该区社会经济的高质量发展。本文对大湾区"9市+2区"近10年的社会经济与水资源现状及其协同演化规律进行分析研究。结果显示：目前大湾区供水主要依赖地表水，水资源的分布与区域经济发展不协调，作为区域发展核心引擎的香港、澳门、深圳（极度缺水）以及广州（重度缺水）人均水资源量过低。广州、佛山、中山、东莞（>80%）以及深圳（>40%）水资源开发利用程度高，水资源供需压力大。通过归因分析得到大湾区的水资源利用现状与社会经济的协同规律：产业结构影响用水结构以及水资源开发利用程度，控制用水效率。区域内产业结构与发展趋势，及其与世界湾区的对比分析验证了产业结构理论中的"配第-克拉克定理"。随着大湾区经济持续的发展与产业结构优化，大湾区用水效率将提高，人均用水量会逐步降低。同时城市公共用水、生活用水需求量将持续上升，需确保大湾区供水设施，供水量及供水安全满足未来社会经济发展需求。     

Estimating Benefits in a Recovering Estuary: Tampa Bay,Florida

Restoration and preservation of riparian forests and coastal marshes provides nutrient removal and other biochemical and physical functions which may preclude, reduce, or delay the need for additional water treatment, while also protecting human health. We examined the ecosystem goods and related potential cost savings for the Tampa Bay community from seagrass expansion (more than 3,100 ha since 1990), coastal marsh, and mangrove restoration/recovery (more than 600 ha since 1990), and habitat that has been maintained or preserved. Habitats in and around Tampa Bay provide nutrient reductions equivalent to just over US$22 million per year in avoided wastewater treatment plant costs. Future accrual of value associated with maintaining the ecosystem good of usable clean water could rapidly increase to as high as ～US$3 billion per year, when one takes into account the additional costs of water treatment and storm water diversion infrastructure that is likely as the region’s population continues to grow. There is additional value accrual close to a quarter million dollars per year based on avoided social costs to the global community due to greenhouse gases sequestered by bay habitats. Most human beneficiaries associated with the maintenance of usable clean water in Tampa Bay are part of the surrounding regional community. The large current and future cost savings for the community surrounding Tampa Bay and additional benefits for the global community speak to the value of maintaining a healthy bay through past and continued restoration and preservation efforts.     

Causes of sinks near Tucson, Arizona, USA

 Land subsidence in the form of sinks has occurred on and near farmlands near Tucson, Pima County, Arizona, USA. The sinks occur in alluvial deposits along the flood plain of the Santa Cruz River, and have made farmlands dangerous and unsuitable for farming. More than 1700 sinks are confined to the flood plain of the Santa Cruz River and are grouped along two north-northwestward-trending bands that are approximately parallel to the river and other flood-plain drainages. An estimated 17,000 m³ of sediment have been removed in the formation of the sinks. Thirteen trenches were dug to depths of 4–6 m to characterize near-surface sediments in sink and nonsink areas. Sediments below about 2 m included a large percentage of dispersive clays in sink areas. Sediments in nonsink areas contain a large component of medium- to coarse-grained, moderately to well sorted sand that probably fills a paleochannel. Electromagnetic surveys support the association of silts and clays in sink areas that are highly electrically conductive relative to sand in nonsink areas. Sinks probably are caused by the near-surface process of subsurface erosion of dispersive sediments along pre-existing cracks in predominantly silt and clay sediments. The pre-existing cracks probably result from desiccation or tension that developed during periods of water-table decline and channel incision during the past 100 years or in earlier periods. Submitted, April 1997 · Revised, November 1997 · Accepted, April 1998     

Future copper resources

Concerns about future supplies of raw materials demand careful examination of underlying assumptions and data. Flawed deposit information, ignored undiscovered resources and questionable assumptions about future consumption require a new look at copper resources.A careful compilation of 1978 copper-bearing mineral deposits totals 2700 million metric tons of copper including past production—considerably more than reported in previous studies. About 69% of the copper is in porphyry copper deposits and 12% in sediment-hosted copper, Magmatic sulfide (mostly intrusive Ni) deposits account for 5.1%, and IOGC adds about 4.7%. VMS deposits represent 45% of the 1978 deposits but only 4.9% of the copper.The largest 20% of the deposits account for over 92% of the total copper metal. In other words, total Cu content in the smaller 1600 deposits is only about 8% of all Cu known in all deposits. This is a consequence of highly skewed frequency distributions of deposit tonnages and contained metals in all kinds of mineral deposits. This relationship is critical if one is concerned about long-term supply of copper. Typically, distributions of contained metal can be modeled well by the lognormal distribution for individual types of deposits.Information used here and in many other studies on copper includes past production. Total past production through 2015 is about 667 million tons Cu. After subtracting past production from the total copper in known deposits, the remaining unproduced copper from known deposits is 2030 million tons. Known deposits inform us about undiscovered copper resources.Over 80% of known copper is in porphyry copper and sediment-hosted copper deposits. A reliable and robust USGS managed global assessment of 225 tracts for porphyry Cu and sediment-hosted Cu produced an expected value estimate of 3500 million tons Cu in undiscovered deposits. Deposit types not assessed such as IOGC are likely to have significant amounts of undiscovered copper. If the proportion of total Cu accounted for by the two major deposit types assessed is the same proportion in all undiscovered deposits, total Cu expected in these other deposit types would add an additional 850 million tons. The reasonable estimate of copper in undiscovered mineral deposits of 4350 million tons when added to the unmined 2030 million tons in known deposits provides an estimate of 6380 million of tons Cu, which far exceeds estimates published by other researchers.Growth in copper production appears to be exponential over time but appears to be linear with respect to population. Demand for copper is not driven by time, but rather by population and per capita income. Rates of population increases are slowing and incomes in many countries are increasing. Per capita consumption of copper will increase over the coming years as populous nations such as China and India develop increasing per capita incomes, but the demand will likely level off as their economies improve. The large estimated copper resources along with evidence of slowing demand for copper over the long term considerably extend the time of “peak copper” and the long mine life of large deposits means the decline in production after will not be rapid. The focus of copper supply concerns should be on important problems such as improving recovery rates, careful consideration of the benefits and costs of mining very large deposits, technologies to increase exploration success in covered areas and reducing costs of underground mining.     

The current status of mapping karst areas and availability of public sinkhole-risk resources in karst terrains of the United States

Subsidence from sinkhole collapse is a common occurrence in areas underlain by water-soluble rocks such as carbonate and evaporite rocks, typical of karst terrain. Almost all 50 States within the United States (excluding Delaware and Rhode Island) have karst areas, with sinkhole damage highest in Florida, Texas, Alabama, Missouri, Kentucky, Tennessee, and Pennsylvania. A conservative estimate of losses to all types of ground subsidence was $125 million per year in 1997. This estimate may now be low, as review of cost reports from the last 15 years indicates that the cost of karst collapses in the United States averages more than $300 million per year. Knowing when a catastrophic event will occur is not possible; however, understanding where such occurrences are likely is possible. The US Geological Survey has developed and maintains national-scale maps of karst areas and areas prone to sinkhole formation. Several States provide additional resources for their citizens; Alabama, Colorado, Florida, Indiana, Iowa, Kentucky, Minnesota, Missouri, Ohio, and Pennsylvania maintain databases of sinkholes or karst features, with Florida, Kentucky, Missouri, and Ohio providing sinkhole reporting mechanisms for the public.     

Transformation of dilative and contractive landslide debris into debris flows—An example from marin County, California

The severe rainstorm of January 3, 4 and 5, 1982, in the San Francisco Bay area, California, produced numerous landslides, many of which transformed into damaging debris flows. The process of transformation was studied in detail at one site where only part of a landslide mobilized into several episodes of debris flow. The focus of our investigation was to learn whether the landslide debris dilated or contracted during the transformation from slide to flow.

The landslide debris consisted of sandy colluvium that was separable into three soil horizons that occupied the axis of a small topographic swale. Failure involved the entire thickness of colluvium; however, over parts of the landslide, the soil A-horizon failed separately from the remainder of the colluvium.

Undisturbed samples were taken for density measurements from outside the landslide, from the failure zone and overlying material from the part of the landslide that did not mobilize into debris flows, and from the debris-flow deposits. The soil A-horizon was contractive and mobilized to flows in a process analogous to liquefaction of loose, granular soils during earthquakes. The soil B- and C-horizons were dilative and underwent 2 to 5% volumetric expansion during landslide movement that permitted mobilization of debris-flow episodes.

Several criteria can be used in the field to differentiate between contractive and dilative behavior including lag time between landsliding and mobilization of flow, episodic mobilization of flows, and partial or complete transformation of the landslide.     

Impact of event landslides on road networks: a statistical analysis of two Italian case studies

Despite abundant information on landslides, and on landslide hazard and risk, in Italy, little is known on the direct impact of event landslides on road networks and on the related economic costs. We investigated the physical and economic damage caused by two rainfall-induced landslide events in Central and Southern Italy, to obtain road restoration cost statistics. Using a GIS-based method, we exploited road maps and landslide event inventory maps to compute different metrics that quantify the impact of the landslide events on the natural landscape and on the road networks, by road type. The maps were used with cost data obtained from multiple sources, including local authorities, and specific legislation, to evaluate statistically the unit cost per metre of damaged road and the unit cost per square metre of damaging landslide, separately for main and secondary roads. The obtained unit costs showed large variations which we attribute to the different road types in the two study areas and to the different abundance of landslides. Our work confirms the long-standing conundrum of obtaining accurate landslide damage data and outlines the need for reliable, standardized methods to evaluate landslide damage and associated restoration costs that regional and local administrations can use rapidly in the aftermath of a landslide event. We conclude recommending that common standardized procedures to collect landslide cost data following each landslide event are established, in Italy and elsewhere. This will allow for more accurate and reliable evaluations of the economic costs of landslide events.     

Environmental benefits vs. costs of geologic mapping

Boone and Winnebago Counties, Illinois, U.S.A., were selected for this study, required by the Illinois State Senate, because mapping and environmental interpretations were completed there in 1981. Costs of geologic mapping in these counties in 1990 dollars were $290,000. Two estimates of costs of statewide mapping were made, one extrapolated from Boone and Winnebago Counties ($21 million), the other estimated on the basis of differences between the Boone/Winnebago program and proposed mapping program for the State of Illinois ($55 million).Benefits of geologic information come in the form of future avoided costs for environmental cleanup. Only the quantifiable data, available from a few sites, were included.Data collection, based on 55 personal interviews in Boone and Winnebago Counties, were grouped into four cumulative categories with increasing variability. Geologic maps alone cannot account for all avoided costs of future cleanup. Therefore, estimated benefits were reduced by 50, 75, and 90 percent in three scenarios. To account for delays in proper utilization of knowledge gained from a mapping program, a 10-yr delay in benefit realization was assumed. All benefits were converted to 1990 dollars.In benefit category 4, benefit-cost ratios for Boone/Winnebago Counties ranged between 5 and 55. Statewide projection of benefits was based on county areas and an aquifer contamination potential score for each county. Statewide benefit-cost ratio in benefit category 4 ranged from 1.2 to 14 ($21 million mapping costs) and from 0.5 to 5.4 ($55 million mapping costs).     

Evaluation on the change characteristics of ecosystem service in Dhanbad district of Jharkhand,India based on land use change

Ecosystem services (ESs) simply refer to those services conferred by Mother Nature for the survival of her offspring living within. But the provision of ESs is continuously affected by human activity and related changes like transformations in land use and land cover. The present study has been initiated to evaluate the pattern of landscape transformation and its impact on ecosystem service, along with estimating the per capita availability of ESs based on remotely sensed data in the Dhanbad district, Jharkhand, India. The result shows that the total ecosystem service value (ESV) loss of the district was $2251959.76 during 1990–2020. The highest loss of ESV was recorded due to the conservation of agricultural land to built-up area ($15884988.50) and vegetation cover on agricultural land ($14451545.01), while the increased vegetation cover on other types of land helped the district to gain back some balance over the loss. But in a smaller scale study, 5 out of the 8 spatial units are facing negative change in ESV, and unfortunately, they are altogether inhabited by more than 85% of the district's total population. That means the loss of ESV is greater where it needs to be more as per population. Moreover, the per capita ESs in the district decreased by 68.48%, while among the spatial units in Dhanbad it decreased the most (89.60%), which is a serious cause for worry in the future. Therefore, this study can contribute to the process of decision-making, proposing ecological conservation and sustainable development plans for the region.