Natural Hazards


Drought

Overview – Drought in Socorro County, New Mexico 
Drought is a condition of climatic dryness that reduces soil moisture, water or snow levels below the minimum necessary for sustaining plant, animal, and economic systems. Drought conditions are usually not uniform over the entire state. Local and regional differences in weather, soil condition, geology, vegetation, and human influence need to be considered when assessing the impact of drought on any particular location. 

Previous Occurrence – Drought 
Identified as a concern by each jurisdiction, no previous drought data exists from those jurisdictions. According to the NCDC, no drought events have been recorded for the county between January 1, 1950 and August 31, 2010. Figures 18 and 19 identify the average amount of precipitation received in Socorro County and just how little precipitation the county receives. 

Socorro County relies upon groundwater for potable water. Current diversion for agricultural uses is approximately 50,000 acre-feet per year. At current consumption rates, the aquifer will continue to yield good water for another 120 years. A severe prolonged drought would greatly impact the entire County’s ability to provide potable water from groundwater sources. 

Identified in the NMDHSEM HMP (2007), the state has experienced droughts since prehistoric times with extended drought conditions evidently causing the collapse of many early civilizations. Periods of drought since 1950 have been documented during 1950-1957, 1963- 1964, 1976-1978, 1989, 1996, 1998-1999, 1999-2003, 2003-2006. In the last 100 years, New 

Mexico has suffered from four devastating periods of drought; 1900-1910, 1931-1941, 1942- 1956, and 1974-1979. A short-term drought was identified that lasted from October 2005 to July 2006. Between 1995 and May 2007, there were three state declared disasters for effects related to drought, primarily for loss of domestic drinking water: May 1996, May 2000, and June 2002. The total cost for drought related events for this time period is $279,459. However, indirect costs are estimated to be between $50 to 100 Million.

Earthquakes

Overview – Earthquake in Socorro County, New Mexico

Earthquakes result from sudden ground motion or trembling caused by a release of strain accumulated within or along the edge of the Earth’s crustal plates. Earthquakes occur most frequently in the boundaries between the great crustal plates that form the earth's outer shell. As these plates move, stress accumulates. Eventually, when faults along or near plate boundaries slip abruptly, an earthquake occurs. Although earthquakes in the United States have caused less economic loss annually than other hazards, they have the potential to cause great, sudden loss in proximity to the epicenter. Within one to two minutes, an earthquake can devastate a city through ground-shaking, surface-fault ruptures, and ground failures. Seismic hazards often trigger other devastating events, such as landslides, fires, and damage to dams and levees. 

New Mexico is a moderately seismically active region, with earthquakes occurring in most parts of the state. The Socorro area has been the most active earthquake region of New Mexico during at least the past 150 years. During the past 45 years, approximately 50% of the seismic energy generated by earthquakes in New Mexico has been released in a region centered near Socorro, encompassing only about 2% of the state's total land area. This relatively high rate of earthquake activity in the Socorro region is due to an inflating sill of molten rock (magma) that is roughly 1300 square miles in area and sits approximately 12 miles beneath the surface of the fault-bounded Rio Grande rift. 

Commercial and residential buildings, as well as critical care and first responder facilities can be toppled or severely damaged during an earthquake. Transportation routes can be damaged or destroyed. Utilities and infrastructure are also vulnerable to damage/destruction by earthquakes. Death and injuries that directly result from earthquakes are unlikely but they can occur indirectly when structures collapse. Casualties typically result from falling objects and debris, or from forces that damage or demolish buildings and other structures. Disruption of communications, electrical power supplies, and gas, sewer, and water lines should be expected in a large earthquake. 

Earthquakes can trigger fires, dam failures, landslides, or releases of hazardous material, compounding their hazards. 

Previous Occurrences – Earthquakes

Though not nearly as big or as numerous as in some other parts of the world, earthquakes have rattled New Mexico over the years. Figure 24 depicts the approximate epicenters for past earthquakes in New Mexico and surrounding areas between 1962 and 2005. Socorro County, specifically the City of Socorro inclusive of New Mexico Tech and the smaller unincorporated areas along the Rio Grande Valley are within the Rio Grande Rift. The Rio Grande Rift is a region of tectonic, volcanic, and seismic activity that extends from north-central Colorado southward to Chihuahua, Mexico. At this point in time, New Mexico inclusive of Socorro County has a short and an incomplete earthquake history established; however, Geologic evidence shows that large earthquakes have occurred in the Rio Grande rift. There are large numbers of active faults along the rift and the probability of a future large earthquake in the rift is likely high. 

Socorro is the earthquake capital of New Mexico. A 5,000 km2 (1,931 mi2) area, less than 2% of New Mexico, surrounding the town has produced nearly 50% of the 30 natural earthquakes of magnitude 4.5 or greater in the state since 1869. Three of these shocks occurred during a very strong swarm from 2 July 1906 through early 1907 and were the strongest within the state from 1869 through 2008. Information on these shocks comes from newspaper accounts and notably from a published paper by the famous seismologist H. F. Reid. His paper on the 1906–07 swarm appears in the first issue of the Bulletin of the Seismological Society of America and presents Rossi-Forel earthquake intensity observations out to distances of several hundred kilometers for the three strong earthquakes of the swarm.

The largest earthquakes of record in this region occurred during an ongoing earthquake swarm in 1906, and the magnitudes of the two largest events were approximately 5.8. For comparison, the largest felt and heard event from the most recent swarm in this region (August 2009) was M 2.6. This earthquake increased the property damage already sustained at Socorro from previous earthquakes. Four rebuilt chimneys were shaken off the Socorro County Courthouse, and two others were cracked severely. Plaster fell at the courthouse, and a cornice on the northwest corner of the two-story adobe Masonic Temple was thrown onto its first floor. Several bricks fell from the front gable on one house. Plaster was shaken from walls in Santa Fé, about 200 kilometers from the epicenter. Felt over most of New Mexico and in parts of Arizona and Texas. (Source: http://earthquake.usgs.gov/regional/states/events/1906_11_15.php; Reid, 1911) 

Earthquake swarms, defined as a series of earthquakes recurring for days in nearly the same location within minutes of each other, are very common in this region. Historical accounts of these swarms date back to the 1860s, and they have been recorded on local seismic instruments since the early 1960s (Figure 25, blue stars, Sanford et al., 2002). The majority of the earthquakes in these swarms are shallow (3-8 miles beneath the surface), and relatively small (M < 1.0). These small earthquakes are not damaging; however, based on historic seismicity and geologic evidence, there is a chance for a larger, possibly damaging event in the future (Wong, 2009). According to the US Geological Survey, there is an 18% chance of a large earthquake (M > 6.0) in the Socorro region in the next 100 years. 

Twelve strong felt earthquakes with estimated magnitudes of 4.5 or greater occurred in the Socorro area from 1869 through 1961. Unlike the instrumental data from 1962 through 2004, nearly all of these strong shocks appear to have had epicenters near Socorro rather than north of San Acacia. Also the statistics for earthquakes with magnitudes of 4.5 or greater from 1869 to the present indicated the Socorro-area seismic activity before the 1930s was significantly higher primarily because of prolonged earthquake swam that commenced in July 1906 a few months following the San Francisco earthquake in April of that year. Earthquakes were felt as early as July 2, 1906 and continued almost on a daily basis well into 1907. Three shocks in the swarm had magnitudes of 5.5 to 5.9, strong enough to significantly damage some adobe and masonry structures. The most unusual characteristic noted of the swarm was the exceptionally large number of felt earthquakes over a six-month period. It is suspected that weak shocks probably related to the swarm continuing into 1909 (Sanford, A.R. 1998). 

During the month August 2009, Seismicity within the Socorro region has been very active. A felt earthquake of magnitude (ML) 2.3 occurred on August 19, 2009 approximately 3 km NE of Socorro near Escondida. Small events continued to occur during this time with activity beginning near the Lemitar area on August 24, 2009. These events have been numerous and fairly shallow depth of 5.5-6 km. The largest event was ML=2.5 on August 29, 2009 at 18:31:01 MDT (August 30, 2009 at 01:31:01 UTC) and was felt by many residents of Lemitar and Socorro. 

Preliminary locations on the largest 53 events (ML range of 0.5 to 2.5); however, over 400 smaller events have also occurred since August 19, 2009. The locations of 53 of the largest earthquakes are very similar, suggesting that this is an earthquake swarm. Earthquake swarms are usually caused in response to tectonic or hydrological pressure changes in the crust. Minor felt earthquakes in this region are not uncommon, and have been documented by Dr. Allan Sanford in the past (Figure 26, blue squares). However, this was a swarm with unusually frequent, large earthquakes (14 earthquakes with ML > 1.4). For a size comparison, felt reports were noted for 4 events with ML 1.9 and greater. Table 46 identifies the strongest earthquakes equal to or greater than 4.5 in Socorro County. 

Earthquake activity was detected in northern Socorro County around the San Acacia, NM area. A series of minor earthquakes measuring between ML 2.1 and less occurred between March 22 and March 23, 1998. Following the first tremor were a series (total of 10) of smaller earthquakes all measuring less than ML 1.0. 

Flood/Flash Floods

Overview – Flood/Flash Floods in Socorro County, New Mexico

Nationwide, hundreds of floods occur each year, making flooding one of the most common hazards in all 50 states and U.S. territories. Most injuries and deaths from flooding happen when people are swept away by flood currents, and most property damage results from inundation by sediment-filled water. The majority of flood events in the United States involve inundation of floodplains (Figure 6) associated with rivers and streams and shoreline inundation along lakes and coastlines. 

This type of flooding typically results from large-scale weather systems generating prolonged rainfall from locally intense storms or snowmelt. For the purposes of this report, this type of flooding is referred to as ―riverine flooding‖ and is characterized by a gradual and predictable rise in a river or stream due to persistent precipitation. After the stream or river overflows its banks, the land nearby remains under water for an extended period of time. Although the State of New Mexico and Socorro County experience riverine flooding,  flash flooding is a more common and a more damaging type of flooding. 

Flash floods are aptly named: they occur suddenly after a brief but intense downpour; they move quickly and end abruptly. Although the duration of these events is usually brief, the damages can be quite severe. People are often surprised at how quickly a normally dry arroyo can become a raging torrent. Flash floods are the primary weather-related killer with around 140 deaths recorded in the United States each year. Flash floods are common and frequent in New Mexico, and as a result, New Mexico has the tenth highest flash flood fatality rate in the nation. 

Flash floods also result as a secondary effect from other types of disasters, including large wildfires. Wildfires remove vegetative cover and alter soil characteristics, increasing the quantity and velocity of storm water runoff. In addition, drought conditions exacerbate flash flooding and erosion due to soils becoming hydrophobic and increasing velocity of storm water runoff. Floods can cause erosion along riverbanks and undermine buildings and bridges, tear out trees, wash out access roads, and cause of loss of life and injuries. 

National Flood Insurance Program

In 1968, Congress created the National Flood Insurance Program (NFIP) in response to the rising cost of taxpayer funded disaster relief for flood victims and the increasing amount of damage caused by floods. The Federal Insurance and Mitigation Administration (FIMA) manage the National Flood Insurance Program (NFIP) and implement a variety of programs authorized by Congress to reduce losses that may result from natural disasters. FIMA is a component of the FEMA manages the NFIP, and oversees the floodplain management and mapping components of the Program. 

Nearly 20,000 communities across the United States and its territories participate in the NFIP by adopting and enforcing floodplain management ordinances to reduce future flood damage. In exchange, the NFIP makes federally backed flood insurance available to homeowners, renters, and business owners in these communities. 

The NFIP Community Rating System (CRS) was implemented in 1990 as a program to recognize and encourage community floodplain management activities that exceed minimum NFIP standards. The National Flood Insurance Reform Act of 1994 codified the CRS in the NFIP. Under the CRS, flood insurance premium rates are adjusted to reflect the reduced flood risk resulting from community activities that meet the three goals of the CRS: (1) reduce flood losses; (2) facilitate accurate insurance rating; and (3) promote the awareness of flood insurance. 

Flood damage is reduced by nearly $1B a year through partnerships with NFIP and CRS communities, the insurance industry, and the lending industry. Buildings constructed in compliance with NFIP building standards also suffer approximately 80% less damage annually than those not built in compliance. Further, every $3 paid in flood insurance claims saves $1 in disaster assistance payments. 

The NFIP is self-supporting for the average historical loss year, which means that operating expenses and flood insurance claims are not paid for by the taxpayer, but through premiums collected for flood insurance policies. The program has borrowing authority from the U.S. Treasury for times when losses were heavy; however, these loans are usually paid back with interest. To obtain secured financing to buy, build, or improve structures in Special Flood Hazard Areas (SFHAs), flood insurance must be purchased. Lending institutions that are federally regulated or federally insured must determine if the structure is located in a SFHA and must provide written notice requiring flood insurance. Flood insurance is available to any property owner located in a community participating in the NFIP. All areas are susceptible to flooding, although to varying degrees. In fact, 25% of all flood claims occur in low-to-moderate risk areas. 

The most widely adopted design and regulatory standard for floods in the United States is the 1% annual chance flood and this is the standard formally adopted by FEMA. The 1% annual flood, also known as the base flood elevation, has a 1% chance of occurring in any particular year. It is also often referred to as the “100-year flood” since its probability of occurrence suggests it should only reoccur once every 100 years (although this is not the case in practice). Experiencing a 100-year flood does not mean a similar flood cannot happen for the next 99 years; rather it reflects the probability that over a long period of time, a flood of that magnitude should only occur in 1% of all years. 

According to FEMA, Socorro County has been an active participant in the National Flood Insurance Program since August 2008. Since participating in the program, 212 NFIP policies were in force in Socorro County (to include Socorro City/Village of Magdalena) as of April 30, 2011, for a total flood insurance coverage of $38,582,500.00. A total of $18,369 has been paid out in Socorro County for flood damage since the establishment of the NFIP in 1978. At present, there are no identified repetitive-loss properties in Socorro County.

Extreme Heat

Overview – Extreme Heat in Socorro County, New Mexico

Socorro County experiences some form of extreme heat activity annually, based on seasonal meteorological patterns and local topographical conditions. All areas of Socorro County are susceptible to extreme heat conditions, although local topography, such as elevation and land contours, plays a significant part in how this extreme heat affects a particular area. For the purpose of this report, all areas of the County are considered equally vulnerable to extreme heat. The effects of extreme temperatures generally affect at risk sectors of the population: the elderly, the young, the sick/infirmed, those living below the poverty level and outdoor laborers. 

Previous Occurrences – Extreme Heat

Socorro’s latitude and altitude combine to give it a pleasant year-round climate. Socorro is just far enough south to be spared many of the storms that often touch northern New Mexico. Its elevation of approximately 4,585 feet spares us the extreme heat. The altitude also provides four distinct but temperate seasons. Socorro summer high temperature averages are in the mid ’90s, with no more than 20 days when the temperature reaches over 100oF. Winter high temperature averages are in the mid ’50s, and winter nights seldom drop to 0oF. Socorro’s low average humidity, little cloud cover, and valley location encourage formation of significant atmospheric stable layers. Normally during the day, air temperature decreases with altitude, but after a clear, calm night, the air next to the ground becomes cooler than the air above. 

During the summer months, individual daytime temperatures quite often exceed 100° F at elevations below 5,000 feet; but the average monthly maximum temperatures during July, the warmest month, range from slightly above 90° F at lower elevations to the upper 70’s at high elevations. Warmest days quite often occur in June before the thunderstorm season sets in; during July and August, afternoon convective storms tend to decrease solar insulation, lowering temperatures before they reach their potential daily high. A preponderance of clear skies and low relative humidities permit rapid cooling by radiation from the earth after sundown; consequently, nights are usually comfortable in summer. The average range between daily high and low temperatures is from 25° to 35° F. 

According to the NCDC, no extreme heat events have been identified. 

Hazard Profile – Extreme Heat Hazard Characteristics

Extreme heat is defined as temperatures that hover 10 degrees or more above the average high temperature for the region and last for several weeks. In an average year, extreme heat kills 175 people (FEMA Extreme Heat Backgrounder). Young children, the elderly, outdoor laborers, and sick people are the most likely to suffer the effects of extreme heat. The heat index measures the severity of hot weather by estimating the apparent temperature: how hot it feels (Table 44). Skin resistance to heat and moisture transfer is directly related to skin temperature, therefore the ambient temperature can be quantified by examining the relation between relative humidity versus skin temperature. If the relative humidity is higher/lower than the base value, the apparent temperature is higher/lower than the ambient temperature. In New Mexico at elevations below 5,000 feet, individual day-time temperatures often exceed 100°F during the summer months. However, during July, the warmest month, temperatures range from slightly above 90°F in the lower elevations to 70°F in the higher elevations (Western Region Climate Center, www.wrcc.dri.edu/narratives/NEWMEXICO.htm). 

Extreme heat, or heat wave, is defined by the NWS as a temperature of 10° F or more above the average high temperature for the region, lasting for several weeks. This condition is definitely a public health concern. During extended periods of very high temperatures or high temperatures with high humidity, individuals can suffer a variety of ailments, including heatstroke, heat exhaustion, heat syncope, and heat cramps. 
  • Heatstroke is a life threatening condition that requires immediate medical attention. It exists when the body’s core temperature rises above 105° F as a result of environmental temperatures. Patients may be delirious, stuporous, or comatose. The death-to-care ratio in reported cases in the U.S. averages about 15% 
  • Heat exhaustion is much less severe than heatstroke. The body temperature may be normal or slightly elevated. A person suffering from heat exhaustion may complain of dizziness, weakness, or fatigue. The primary cause of heat exhaustion is fluid and electrolyte imbalance. The normalization of fluids will typically alleviate the situation 
  • Heat syncope is typically associated with exercise by people who are not acclimated to exercise. The symptom is a sudden loss of consciousness. Consciousness returns promptly when the person lies down. The cause is primarily associated with circulatory instability because of heat. The condition typically causes little or no harm to the individual 
  • Heat cramps are typically a problem for individuals who exercise outdoors but are unaccustomed to heat. Similar to heat exhaustion, it is thought to be a result of a mild imbalance of fluids and electrolytes 
The elderly, disabled, and debilitated are especially susceptible to heat stroke. Large and highly urbanized cities can create an island of heat that can raise the area’s temperature by 3 to 5° F. Therefore, urban communities with substantial populations of elderly, disabled, and debilitated people could face a significant medical emergency during an extended period of excessive heat. 

New Mexico is partially an arid desert state, and summer temperatures often exceed the 100° F mark under normal conditions. Nighttime temperatures are typically cool due to low humidity, and even though daytime temperatures may be high, people experience relief at night. Heat waves in which daily high temperatures exceed 110o F for many days in a row are rare. Such a heat wave in the higher altitudes would probably have a more damaging effect because people would not be expecting such hot conditions. However, anywhere in the state that experienced the humidity/temperature combination could suffer ill effects from the event. 

A heat wave would also have a drying effect on vegetation, facilitating the ignition of wildfires. If a heat wave were coupled with a power failure, the effect on the population would be much more severe due to a lack of air conditioning. In general, it is safe to say that there is no area of the state that is immune from the hazard of heat wave (Figure 22). Heat can affect roadways, runways, and some equipment, but it is generally a health risk, not a structural hazard. Periods of extreme heat can also place additional demands upon the electrical grid. Brown outs and black outs could dramatically increase vulnerability, particularly to those facilities associated with the housing and care of vulnerable populations. 

Location

The entire planning area is subject to extreme heat events. Research has concluded that no past history exists at this time. Future updates to the mitigation plan will include extreme heat events experienced in Socorro County and those jurisdictions identified in this HMP.

High Wind

Overview – Wind in Socorro County, New Mexico

Wind is defined as the motion of air relative to the earth’s surface, and the hazard of high wind is commonly associated with severe thunderstorm winds (exceeding 58 mph) as well as tornadoes, hurricanes, tropical storms and nor’easters. High winds can also occur in the absence of other definable hazard conditions, events often referred to as simply “windstorms.” High wind events might occur over large, widespread areas or in a very limited, localized area. They can occur suddenly without warning, at any time of the day or night. 

Typically, high winds occur when large air masses of varying temperatures meet. Rapidly rising warm moist air serves as the “engine” for severe thunderstorms, tornadoes and other windstorm events. These storms can occur singularly, in lines or in clusters. They can move through an area very quickly or linger for several hours. 

Previous Occurrences – High Winds

Socorro County experiences some form of high wind activity annually, based on seasonal meteorological patterns and local topographical conditions. The County is susceptible to high wind events. All areas of Socorro County are susceptible to high wind conditions, although local topography, such as elevation and land contours, plays a significant part in how high winds affect a specific area. For the purpose of this report, all areas of the County are considered equally vulnerable to high wind events. 

The effects of high wind storms can topple manufactured homes, destroy buildings, lift cars, snap trees (which create roadblocks), topple power lines (can cause an electrocution hazard and cripple local infrastructure), and cause injury and death. 

According to the NCDC, Socorro County has not experienced any high wind events but, however, NCDC does show four tornado events between 1950 and 2005 (Table 39). The only reported damage was for the first event in 1950 which caused $25K in property damage. Additionally the 1950 reported tornado was the only one listed as an F1 with moderate severity while the other three were listed as F0 minimal severity. Tornado was not identified by the MPG as a natural hazard concern. Based on minimal past occurrences and magnitude of the wind event, this could be considered other than a tornado. As future revisions of this plan occurs, should the county experience an increase of tornado events, the MPG will profile tornados and provide a more detailed data of past occurrences and vulnerabilities in the county. 

Reports

December 2009 – As reported by the Mountain Mail, after a weekend of wintry weather, high winds were a cause of concern for many county residents, especially those traveling on Highway 60, which had to be shut down near Magdalena for over an hour. The closure was the result of diesel fuel leaking from the tank of a wrecked semi tractor trailer. According to the Magdalena Marshal, two semis were blown off the road; one at mile marker 126, and the other at mile marker 119. The semi at 119 leaked 240 gallons of diesel fuel causing the highway had to be closed until the hazmat operation had been completed. The truck driver from Boise, Idaho, said he was on his way to Tucson when he experienced the estimated 100 mph gusts on Highway 60. Higher winds were recorded at other stations in the county. Magdalena Ridge Observatory sustained wind speeds at the 10,600 foot facility averaged about 100 mph over a seven hour period with gusts up to 128 mph.

July 15, 2010 – As reported in the local newspaper the El Defensor Chieftain, a fierce storm that blew through Socorro Thursday evening (July 15), ripping the roof off an abandoned single- wide mobile home on Blue Canyon Road and slammed it onto the roof of another home, which sits just below that structure. Additionally, the Socorro Electric Cooperative was called out to a three-phase pole that was down near the Mounyo Ranch off U.S. 380. New Mexico Tech also reported outages due to the down power lines. 

April 29, 2010 – As reported in the local newspaper the El Defensor Chieftain, strong winds tore away some roof paneling at the Veguita Trading Post which severed the wires to the store's satellite system and knocked out some of its electricity. Before finding a resting spot across N.M. 304, the paneling slammed into the back door of a delivery van that store owner moments earlier was helping to unload. The paneling smashed out a window in the van's door. It was reported that customers were battling sustained 40 mph winds. 

January 22, 2010 – The Village of Magdalena experienced high winds during a winter storm (Figure 16). A local resident captured the damage to a local business. The roof was literally peeled off with the north end left attached. No estimated costs were available from this damage. 

January 12, 2010 – As reported in the local newspaper the El Defensor Chieftain, sustained winds of 50 mph with higher gusts, swept through the area damaging roofs and knocking down fences. No injuries were reported. 

July 30, 1997 – Categorized in the NCDC as thunderstorm wind and not high wind, the City of Socorro experienced a strong storm that caused a mobile home to overturn and land on a car and caused downed power lines in the area. No injuries or fatalities were recorded the wind storm (thunderstorm wind) caused $60K in property damage.
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