Geological & Hydrometerological Hazards PDF

Lesson Explain Different Types of 1 Geological Hazards Geological hazards are natural phenomena that cause major problems around the world. The expansion and development of cities has led to an increase in impact and damage due to geological hazards. In general, most of...

Lesson Explain Different Types of 1 Geological Hazards Geological hazards are natural phenomena that cause major problems around the world. The expansion and development of cities has led to an increase in impact and damage due to geological hazards. In general, most of the geological hazards are related to natural conditions, although some may be due to human activities. While landslides come in various names such as mudslide, flash flood, avalanche, etc. The actual difference is in their composition provided that there is an inclined terrain. Sinkholes, on the other hand, can occur on elevated or flat surfaces and can range from massive to barely noticeable which may leave a dent, a hole, or a body of water on the ground. Therefore, as a student you need to be aware of the different types of landslides and sinkholes in order to be prepared for the danger that it may cause. 5 CO_Q2_DRRR SHS Module 1  What is It ❖ Landslide A landslide is a ground movement on a sloping terrain. It does not happen on flat ground because of the angle on the ground, gravity induces the land to move downward. It is aggravated by rain because water is a natural agent for erosion. If rain or any source of water frequently flows down a sloping area, the gravitational descent of loosened soil makes it possible for landslide to occur. Structures that are built on steep-slope mountains have a high vulnerability to landslide hazards especially during heavy rains. Areas with: steep slope, dense population and denuded terrain are distinguished by a high susceptibility to rainfall-induced landslide hazards. Long or regular rain may saturate the topsoil and the bedrock, weakening the soil base of buildings or structures. Without plants and trees whose roots can absorb water and hold the soil together, subsequent rain water can continue to loosen up the soil that anchors the buildings. A heavy downpour of rain can quickly destroy these buildings and communities, giving way to landslides, mudslides, or mudflows. Types of Landslide 1. Soil Creep Landslide is a very slow downslope movement of particles that occurs in every slope covered with loose, weathered material (Britannica dictionary). 2. Slumping Landslide is a downward movement of rock debris, usually the consequence of removal of buttressing earth at the foot of a slope of unconsolidated material (Britannica dictionary). 8 CO_Q2_DRRR SHS Module 1  3. Debris Flow Landslide happens when the slope becomes saturated with water, this then triggers a landslide of water-soaked mass of rock and soil that slides down the slope. 4. Rock Fall landslides are sudden slides caused by heavy rain the rock on the slope loosens and then slides down the slope. ❖ Sinkhole A sinkhole is a topographic depression created when groundwater dissolves the underlying limestone bedrock. Often known as "sink" or "doline,". Characteristics: occur in areas where the soil foundation is made of soft minerals and rocks such as limestone, salt beds, or any acidic rocks. The depth of sinkholes ranges from a couple of meters to several mile deep. How it occurs: Water from the rainfall seeps underneath the soil through the cracks and fissures. As water passes through these cracks and fissures, it erodes the soil and forms a conduit system, these underground water systems increase in size as the soil is carried by the water through internal erosion. This can either form a void filled with air with an underground drainage. If the void is clogged with clay, then it forms a depression which then accumulates water and forms a pond. Otherwise it forms a hole once the cover collapses into the void which can be either filled with air or water. 9 CO_Q2_DRRR SHS Module 1  Types of Sinkholes There are three main types of sinkholes, according to the geologist, but there is an additional category, the artificial sinkholes which are caused by human activity. 1. Cover Collapse Sinkhole It develops suddenly (over an hour period) thus, causing catastrophic damage. 2. Cover Subsidence Sinkhole It gradually grows where the sediment covers are permeable and contain sand. 3. Dissolution Sinkhole It occurs in areas where calcareous is exposed on the ground or where thin layers of soil and permeable sand are also covered. Limestone or dolomite dissolution is most intense when the water first reaches the rock surface. 4. Artificial Sinkhole Such types of sinks may be caused by various human activities, including groundwater pumping and building. What’s More Activity 3: Modified TRUE or FALSE Read each item carefully and choose the best answer. Write your answer on a separate sheet of paper. Write TRUE if the statement is correct. If the statement is false, change the underlined word/s to make the statement true. ___________1. An avalanche is a form of landslide. ___________2. Sinkholes form in sedimentary rock deposits. ___________3. A earthquake is a topographic depression created when groundwater dissolves the underlying limestone bedrock ___________4. Landslide does happen on flat ground because of the angle on the ground, gravity induces the land to move downward. ___________5. One of the characteristics of landslide is the depth of holes ranges from a couple of meters to several mile deep. ___________6. Debris Flow Landslides are sudden slides caused by heavy rain the rock on the slope loosens and then slides down the slope. ___________7. Rock Fall Landslide happens when the slope becomes saturated with water, this then triggers a landslide of water-soaked mass of rock and soil that slides down the slope. 10 CO_Q2_DRRR SHS Module 1  What is It There are different causes of landslide and sinkhole. Any of the triggers are only caused by a triggering element. A landslide can be caused by a natural or mechanical factor / human. Natural causes of landslides can be due to Climate, Earthquakes, Weathering, Flooding, Volcanic Activity, Forest Fires and Gravity while Humans triggered landslides triggered by mining or clear cutting of trees. In this lesson, we will discuss the causes of geological hazards such as landslides and sinkholes. Types of landslide will also be addressed with you so that you will be able to determine the various effects of rainfall-induced landslides and so that you will be able to determine the soil or soil response in such a situation. It is crucial that you know the various cause of landslide so that you can also process the interaction of these causes with each other in mind. CAUSES OF GEOLOGIC HAZARDS  LANDSLIDE NATURAL CAUSES OF LANDSLIDES – Climate Long-term climatic changes can significantly impact soil stability. A general reduction in precipitation leads to lowering of water table and reduction in overall weight of soil mass, reduced solution of materials and less powerful freeze-thaw activity. A significant upsurge in precipitation or ground saturation would dramatically increase the level of ground water. When sloped areas are completely saturated with water, landslides can occur. If there is absence of mechanical root support, the soils start to run off. – Earthquakes Seismic activities have, for a long time, contributed to landslides across the globe. Any moment tectonic plates move, the soil covering them also moves along. When earthquakes strike areas with steep slopes, on numerous occasion, the soil slips leading to landslides In addition, ashen debris flows instigated by earthquakes could also cause mass soil movement. – Weathering It is the natural procedure of rock deterioration that leads to weak, landslide-susceptive materials. It is brought about by the chemical action of water, air, plants and bacteria. When the rocks are weak enough, they slip away causing landslides. 9 CO_Q2_DRRR SHS Module 2 – Erosion Erosion caused by sporadic running water such as streams, rivers, wind, currents, ice and waves wipes out latent and lateral slope support enabling landslides to occur easily. – Volcanic eruption If an eruption occurs in a wet condition, the soil will start to move downhill instigating a landslide. Stratovolcano is a typical example of volcano responsible for most landslides across the globe. Volcanic gases partially dissolve in groundwater which turns into acidic hydrothermal systems that weakens rock by altering minerals to clay. – Forest fires Burns vegetation that holds soil in place. Since it takes time for vegetation to re-establish on steep slopes, the risk of landslides prevails or up to 20 years in dry climates. Wildfire removes the protective ability of vegetation which increases runoff, erosion, and debris flow because the water cannot penetrate through the soil thus carrying the debris downslope. burrowing insects also play a role by aerating the soil destabilizing it during a wildfire because they tend to seek for cooler soil to survive. – Gravity Steeper slopes coupled with gravitational force can trigger a massive landslide. Steeper slopes can also cause the debris to move farther from the foot of the area. HUMAN CAUSES OF LANDSLIDES – Mining Mining activities that utilize blasting techniques contribute mightily to landslides. Vibrations emanating from the blasts can weaken soils in other areas susceptible to landslides. The weakening of soil means a landslide can occur anytime. Earthwork alters the shape of a slope, imposing new loads on an existing slope. – Clear cutting Clear cutting is a technique of timber harvesting that eliminates all old trees from the area. This technique is dangerous since it decimates the existing mechanical root structure of the area. It changes the amount of water infiltrating the soil. 10 CO_Q2_DRRR SHS Module 2  Rainfall-Induced landslides are the most common and widespread damaging landslides in the Philippines, with an average of 20 typhoons each year due to prolonged or heavy rainfall. Most rainfall- induced landslides are shallow (less than a few meters deep), thin, and move quickly. Rainfall can be a cause for landslides, but soil conditions are also very critical. Researchers wanted to take into account a number of variables, including weather type, soil type and land-cover characteristics. However, there was no single source for the data they needed. The features of precipitation occurrences, including the accumulated volume of rainfall, length and severity, and the slope of the terrain show the greatest effect on the stability of the slope and the rate of occurrence of landslides and debris. In addition, the precipitation-induced landslide depends on the type of land covered and the type of soil. In short, the cause of rainfall-induced landslides still rely on the factors mentioned. Types of Landslide 1. Soil Creep Landslide is a very slow downslope movement of particles that occurs in every slope covered with loose, weathered material (Britannica dictionary). The level of creep induced by one rainfall has a strong association with the amount of rainfall and changes in soil moisture. For the valley-head slope, the dirt creeps down and accumulates a hollow portion of the head at the bottom of the bottleneck, under which the dirt is compressed and forms a wave- shaped soil. 2. Slumping Landslide is a downward movement of rock debris, usually the consequence of removal of buttressing earth at the foot of a slope of unconsolidated material (Britannica dictionary). 11 CO_Q2_DRRR SHS Module 2 3. Debris Flow Landslide happens when the slope becomes saturated with water, this then triggers a landslide of water-soaked mass of rock and soil that slides down the slope. Colluvial landslide in a debris flow valley is a common occurrence that is quickly caused by rainfall. The direct destructiveness of this type of landslide is limited, but if failure occurs, the resultant blockage of the channel can lead to a series of magnified secondary hazards. For this cause, it is important to explore the possible response of this type of landslide to rainfall. 4. Rock Fall landslides are sudden slides caused by heavy rain the rock on the slope loosens and then slides down the slope. 12 CO_Q2_DRRR SHS Module 2  SINKHOLE NATURAL CAUSES OF SINKHOLE – Dissolution of sedimentary rocks  Sinkholes occur when sedimentary rocks are dissolved. When these rocks are dissolved, it can either form a void of water or air. A void filled with air forma a hole and a void filled with underground water makes a lake or a pond. Sinkholes can be in the form of holes or depressions on the ground. HUMAN CAUSES OF SINKHOLE – Underground water pumping  Pumping water underneath the ground causes drainage to alter their flow which causes the soil to be eroded by water. Broken pipes underneath the ground can also cause internal erosion making a void underneath the ground. Altering drainage systems cause water to branch into other routes where there is soluble rock can cause erosion through the flow of water. Types of Sinkholes - Different types of sinkholes are made by various causes. 1. Cover Collapse Sinkhole Develop abruptly (over a period of hours) and thus cause catastrophic damages. They occur where the covering sediments contain a significant amount of clay. Over time, surface drainage, erosion, and deposition of sinkhole into a shallower bowl-shaped depression 2. Cover Subsidence Sinkhole Develop gradually where the covering sediments are permeable and contain sand. In areas where cover material is thicker or sediments contain more clay, cover-subsidence sinkholes are relatively uncommon and therefore may not be seen frequently. They are smaller and thus may go undetected for long periods. 13 CO_Q2_DRRR SHS Module 2 3. Dissolution Sinkhole Occur in areas where limestone is exposed at land surface or also is covered by thin layers of soil and permeable sand. Dissolution of the limestone or dolomite is most intensive where the water first contacts the rock surface. Aggressive dissolution also occurs where flow is focused in pre-existing openings in the rock, such as along joints, fractures, and bedding planes, and in the zone of water-table fluctuation where groundwater is in contact with the atmosphere. Solution sinkholes are generally small in size and also slow to develop. 4.Artificial Sinkhole These types of sinkholes can be caused by various human activities, including groundwater pumping and construction activities. However, the most common activities that result in artificial sinkholes are mining, drilling, considerable changes in weight, as well as a tremendous increase in water flow, such as a construction of an artificial pond. 14 CO_Q2_DRRR SHS Module 2  What is It HYDROMETEOROLOGICAL HAZARDS The Philippines being located in the Southeast Asia is considered very vulnerable to natural hazards and disasters, which include typhoons, earthquakes, floods, volcanic eruptions, landslides, and fires that affect the country and its inhabitants. Surrounding the Pacific Ocean basin is a circular arm of active volcanoes known as the “Pacific Ring of Fire” in which most of the volcanoes in the Philippines are part of. Continental plate activities around this area result to volcanic eruptions and tsunamis in the country. National Disaster Management Plan of 2016 stated that HYDROMETEOROLOGICAL is a process or phenomenon of atmospheric, hydrological or oceanographic nature that may cause loss of life, injury or other health impacts, property damage, loss of livelihoods and services, social and economic disruption, or environmental damage. Hydrometeorological hazards include: 1. Typhoon 2. Thunderstorm 3. Flood 4. Flashflood 5. Storm Surge 6. El Niño 7. La Niña Hydrometeorological conditions lead to other hazards such as landslides, fires, plagues, epidemics and in transport and dispersal of toxic substances and volcanic eruption material. Page 10 of 33  Signs of Impending Hydro-meteorological Hazards A. Tropical cyclone, also called typhoon or hurricane, an intense circular storm that originates over warm tropical oceans and is characterized by low atmospheric pressure, high winds, and heavy rain. Philippine Atmospheric Geophysical and Astronomical Services Administration (PAGASA) stated that WEATHER FORECAST is a scientific estimate of future weather condition, wherein a weather condition is a state of the atmosphere at a given time expressed in terms of the most significant variables. In the Philippines, cloudiness, rainfall and wind are the weather parameters with significant variation, and therefore of interest to the forecast users. How is a Weather Forecast Made? Weather forecasting is done by a Meteorologist; he/she must know about the existing weather condition over a large area. The accuracy of forecast decision is based on forecasting tools known as the Weather Map. The weather map displays the air pressure, wind, temperature, and humidity distribution trends at various atmospheric rates. There are two forms, namely the surface map and the upper-air maps, of the basic weather map. Weather forecasting comprises of 5 steps as follow: 1st Step: Observation A meteorologist forecasts weather decision through surface observations at least every three hours over land and sea, and upper air stations at least every twelve hours. Meteorological satellites, geostationary and polar orbiting, take pictures of the cloud imagery of the atmosphere. These satellites take pictures of the cloud formations of the earth every hour, and continually, respectively. Weather radars are also used to track the position of the atmosphere within radar range. A numerical weather prediction is fed to the computer which analyzes data as programmed and makes a time integration of physical equations. 2nd Step: Collection and Transmission of Weather Data Collection and Transmission of Weather Data are condensed into coded figures, symbols and numerals are transmitted via radiophone, teletype, facsimile machine or telephone to designated collection centers for further transmission to the central forecasting station. Weather satellite images are transmitted to receiving stations on the ground while radar measurements are transmitted through a local communication network to forecast centers. Page 11 of 33 3rd Step: Plotting of Weather Data Observations on land and sea are plotted on charts of surface or mean sea level, which are prepared four times a day. Once the coded messages have been received, they are decoded, and each set of observations is plotted over the respective areas or regions in symbols or numbers on weather charts. Observations of radiosonde, theodolite, aircraft, and satellite wind are plotted on top-level charts that are prepared twice daily. 4th Step: Analysis of Weather Maps, Satellite and Radar Imageries and Other Data Current weather maps are analyzed through different weather charts namely SURFACE (MSL) CHART, where data plotted on this weather map are analyzed isobarically. This means the same atmospheric pressure at different places are inter- connected with a line taking into consideration the direction of the wind; UPPER AIR CHARTS, data plotted on this weather map are analyzed using streamline analysis; NUMERICAL WEATHER PREDICTION MODEL OUTPUT, the computer-plotted weather maps are analyzed manually so that weather systems like cyclones and anticyclones are located; and MONITOR WEATHER CHARTS, plotted cross-section data, rainfall charts and 24 hour pressure change charts are analyzed to determine wind wave movement, rainfall distribution and atmospheric pressure behavior. Page 12 of 33  https://www.namria.gov.ph/jdownloads/Others/PGM2016- _a_new_geoid_model_for_the_philippines_docx.pdf 5th Step: Formulation of the Forecast Upon completion of review of all available meteorological information / data, the preparation of forecasts follows. The first and one of the preliminary steps is to determine the position of the various weather systems and the actual weather over a given area as accurately as the data permits. Department of Science and Technology, “HOW A WEATHER FORECAST IS MADE”, December 2014, http://bagong.pagasa.dost.gov.ph/learning-tools/how-weather-forecast-made Page 13 of 33 B. THUNDERSTORM This is a powerful, short-lived weather disturbance, almost always associated with lightning, thunder, dense clouds, heavy rain or hail, and fast, roaring winds. Thunderstorms occur when layers of dry, moist air rise to cooler regions of the atmosphere in a broad, rapid updraft. Thunderstorm forms through 3 stages known as CUMULUS STAGE, MATURE STAGE and DISSIPATING STAGE. Cumulus Stage where the sun heats the Earth's surface during the day and warms the air around it. MATURE STAGE A cumulus cloud becomes very large, where the water therein becomes large and heavy, and raindrops begin to fall through the cloud when the rising air can no longer hold them up. DISSIPATING STAGE After 30 minutes, thunderstorm begins to dissipate, this occurs when the downdrafts in the cloud begins to dominate over the updraft. Since warm moist air can no longer rise, cloud droplets can no longer form. Page 14 of 33 C. FLOOD & FLASHFLOOD Flood is a high-water stage in which water overflows its natural or artificial banks onto normally dry land, such as a river inundating its floodplain. The effects of floods on human well-being range from unqualified blessings to catastrophes. The Editors of Encyclopaedia Britannica, “FLOOD”, Encyclopædia Britannica, Inc, Encyclopædia Britannica, April 30, 2020, https://www.britannica.com/science/flood Here are the main types of floods to look out for: 1. Inland flooding is the technical name for ordinary flooding that occurs in inland areas, hundreds of miles from the coast. 2. Flash floods are caused by heavy rain or the sudden release of water over a short period of time. The name "flash" refers to their fast occurrence and also to their raging torrents of water that move with great speed. Flash floods are also caused by heavy precipitation in a short period of time, usually less than 6 hours. 3. River flooding occurs when water levels in rivers, lakes, and streams rise and overflow onto the surrounding banks, shores, and neighboring land. 4. Coastal flooding is the inundation of land areas along the coast by seawater. 5. Urban flooding occurs when there is a lack of drainage in an urban (city) area. Means, Tiffany. "The Types of Flood Events and Their Causes." ThoughtCo, Feb. 11, 2020, thoughtco.com/the-types-of-flood-events-4059251 D. STORM SURGE Storm surge or "Daluyong ng Bagyo" in the Philippine system where the irregular sea-level rise during tropical cyclone or "bagyo" occurs. When the tropical cyclone reaches the coast, powerful winds force the ocean water over the coastal low-lying areas, which can lead to flooding. PAGASA takes many technological considerations into account when forecasting the negative impacts of a storm surge. For storm surge prone communities, the most important considerations are the strength of the tropical cyclone; the height of the surge, and the community located in the low-lying area. Page 15 of 33  The infographic below discusses the STORM SURGE WARNING LEVELS, PAGASA (2019). Gen11 Storm Surge Warning System. https://media.philstar.com/ photos/2019/06/17/gen11-storm-surge-warning-system_2019-06-17_23-15- 34.jpg. Retrieved June 30, 2020. Page 16 of 33 E. EL NIÑO & LA NIÑA EL NIÑO- means The Little Boy, or Christ Child in Spanish. El Niño was originally recognized by fishermen off the coast of South America in the 1600s, with the appearance of unusually warm water in the Pacific Ocean. The name was chosen based on the time of year (around December) during which these warm waters events tended to occur. The term El Niño refers to the large-scale ocean-atmosphere climate interaction linked to a periodic warming in sea surface temperatures across the central and east-central Equatorial Pacific. LA NIÑA – means The Little Girl in Spanish. La Niña is also sometimes called El Viejo, anti-El Niño, or simply "a cold event." La Niña episodes represent periods of below-average sea surface temperatures across the east-central Equatorial Pacific. Global climate La Niña impacts tend to be opposite those of El Niño impacts. In the tropics, ocean temperature variations in La Niña also tend to be opposite those of El Niño. Moravchik, Bruce, “WHAT ARE EL NIÑO AND LA NIÑA?”, National Oceanic and Atmospheric AdministrationU.S. Department of Commerce, October 2017, https://oceanservice.noaa.gov/facts/ninonina.html El Niño and La Niña: What Are They? Both El Niño and La Niña are opposite results of ENSO (El Niño Southern Oscillation), the same phenomenon. They are an oscillation in temperatures between the Eastern Equatorial Pacific region's atmosphere and ocean, roughly between the International Dateline and 20 degrees west. Building up between June and December, El Niño is caused by a change in wind patterns. Here, after Asia's summer monsoons, the Pacific Trade Winds struggle to replenish. The moist air contributes to an oscillation between the colder and warmer waters, resulting in warmer than average ocean temperatures. Mason, Matthew, “EL NIÑO AND LA NIÑA: THEIR IMPACT ON THE ENVIRONMENT”, Environmental Science, April 2017, https://www.environmentalscience.org/el-nino-la-nina- impact-environment Page 17 of 33 El Niño & La Niña Affect Health Conditions Extreme climatic conditions are characterized by the El Niño phenomenon; high temperature rises with a little rainfall, and extremely heavy rainfall occurs at the opposite end. According to the Philippines Department of Health, El Niño effects health such as Diseases related to water scarcity or shortage such as diarrhea and skin diseases Red Tide Blooms : Paralytic shellfish poisoning Disorders associated with high temperatures: heat cramps, heat exhaustion, exertional heat injury and heat stroke Department of Health, “EL NINO PHENOMENON”, Department of Health.gov.ph, February 17, 2015, https://www.doh.gov.ph/Health-Advisory/El-Nino-phenomenon La Niña is a weather phenomenon characterized by unusually cold ocean temperature in the Equatorial Pacific which causes increased numbers of tropical storms in the Pacific Ocean. According to the Philippines Department of Health, La Niña effects Health through Disease related to contaminated water due to flooding, such as acute gastroenteritis, typhoid fever, cholera and hepatitis A; Disease related to wading in floodwaters contaminated with urine of infected animals, such as leptospirosis; Disease brought by mosquitoes, such as dengue and malaria; Accidents and injuries such as contusions, lacerations, fractures, electrocution. Stronger winds along the equatorial region, especially in the Pacific, Decreased convection in the Pacific leading to a weaker jet stream temperatures are above average in the southeast and below average in the northwest, Conditions are more favourable for hurricanes in the Caribbean and central Atlantic area, Greater instances of tornados in those states of the US already vulnerable to them Department of Health, “LA NINA PHENOMENON”, Department of Health.gov.ph, February 17, 2015, https://www.doh.gov.ph/Health-Advisory/La-Nina-phenomenon Page 18 of 33