Mass Wasting in China - Case Study

A huge mudslide struck Zhouqu, in Gansu, western China on August 7. More than 1,200 people were declared dead and 490 were missing by August 16. This was the worst landslide in Zhouqu and possibly the worst in China over the passed 60 years.

Zhouqu has experienced many disasters in the recent decades, as it is one of China’s landslide hotspots. The landslide occurred for a number of different reasons. China’s topography is extremely mountainous. Forests have been logged for trees as an industry, stripping the mountainsides and exposing underlying soils and sediments. The weather had been experiencing torrential rains from the monsoon season. The region also experiences large earthquakes. The heavy rainfall and earthquakes occurring on steep slopes where there is slipping soil causes landslides. The anthropogenic causes of landslides are dams, clear cutting, undercutting, etc.

Soldiers have been using explosives to blast through debris that partly dammed the Bailong River and created an unstable lake.  It eventually overflowed and sent a wave of water engulfing the town of Zhouqu early on Sunday.

Meanwhile, specialists in epidemic prevention and medical workers have been sent to the area amid growing fears that contaminated water could spark an outbreak of disease.

This landslide has been devastating as it resulted in many deaths and injuries. Authorities face a growing problem of where to house survivors. More than 1,000 homes were damaged or destroyed and another 3,000 were flooded.

More than 4,000 tents have been sent to Zhouqu but the mountainous terrain means there is little open space to set up camps.

Li Hui, head of the province’s Housing and Urban-Rural Development Bureau, said the new system would provide 12,000 tones of water a day. Safe drinking water will be available within five months.

This landslide could have been prevented from stabilizing the ground and by building retaining walls that won’t compromise the shear plane of the land. Communities could have prevented damage by the landslide by avoiding houses being built on a slope or close by one.

Families are asked to avoid returning to homes because there could be massive destruction. Many prevention programs are created to prevent a future disaster. Recovery efforts and assistance is available from other cities and service workers.

Case Study: Land subsistence in the American Southwest

Land subsidence is the lowering of the land-surface elevation from changes that take place underground. Human activity pumping water, oil, and gas from underground reservoirs; dissolution of limestone aquifers (sinkholes); collapse of underground mines; drainage of organic soils; and initial wetting of dry soils (hydrocompaction) are all common causes of land subsidence. Overdrafting of aquifers is the major cause of subsidence in the southwestern United States. As ground water pumping increases, land subsidence increases as well. In many aquifers, ground water is pumped from pore spaces between grains of sand and gravel. If an aquifer has beds of clay or silt within or next to it, the lowered water pressure in the sand and gravel causes slow drainage of water from the clay  and silt beds. Land subsidence has been getting worse over the passed few years because large amount of ground water has been excessively withdrawn from aquifers. Reduced water pressure is a loss of support for the clay and silt beds, since these beds are compressible they compact and it results with a lowering of the land surface.

Land subsidence has many impacts including changes in elevation and slope of streams, canals, and drains; damage to bridges, roads, railroads, storm drains, sanitary sewers, canals, and levees; damage to private and public buildings; and failure of well casings from forces generated by compaction of fine-grained materials in aquifer systems. Subsidence has resulted in tides moving into low-lying areas that were previously above high-tide levels, in some coastal areas.

In some areas where ground water pumping has causes subsidence, switching from ground water to surface water supplies has stopped the subsidence. If surface water is not available, then other means must be taken to reduce subsidence. Possibilities include reducing water use and determining locations for pumping and artificial recharge that will minimize subsidence. 

Water Use in Agriculture

Drip irrigation is the most common type of “micro-irrigation”. This method includes water running through small horizontal pipes (with holes in them) either buried or lying slightly above the ground next to the crops that slowly drip water onto the crops roots and stems.

            Pros:

·      Is low pressure, low volume irrigation system suitable for high-return value crops such as fruits and vegetable crops.

·      Can increase yields and decrease water, fertilizer and labor requirements.

·      Applies water only to the plants root zone, saving water because of the high application efficiency and high water distribution

·      Any water-soluble fertilizer may be injected through a micro-irrigation system.

           

            Cons:

·      Costly investment

·      Requires frequent maintenance

·      Requires constant monitoring

Sprinkler Irrigation is a method of applying irrigation water, which is similar to rainfall. Water is distributed through a system of pipes usually by pumping. It is then sprayed into the air and irrigated entire soil surface through spray heads so that it breaks up into small water drops, which fall to the ground.

            Pros:

·      Low pressure to save energy

·      Achieves high uniformity of application

·      Water irrigated efficiently if combined with a scheduling system

·      Easy to apply

·      Fixed systems are cheaper to manage

            Cons:

·      Higher capital costs

·      Needs care in windy conditions so uniformity isn’t distorted

Surface irrigation is one of the oldest methods, where farmers flow water down small trenches running through their crops.

            Pros:

·      Cheap / low-tech method

·      Less water is lost to evaporation

·      Less affected by climate and water factors

·      Easy to see effectiveness

            Cons:

·      More water can be lost from runoff at the edges of the fields

·      More labor required

·      Drainage could be an issue

·      May be a higher disease pressure

My Opinion:

I would say sprinkler irrigation is the best of the three for farmers use. I chose this method because it has the most pros and the least cons, so it would be the best choice in my opinion. Sprinkler irrigation has low pressure to save energy, achieves high uniformity of application, is a scheduled system, is easy to apply and is cheap to manage. The main downside of this method is that it is costly however the efficiency is great; therefore sprinkler irrigation would be the best of the three methods.

Rhine River Case Study

The River Rhine rises in the Swiss Alps about 3,353 meters above sea level and flows north, passing through or bordering Switzerland, Liechtenstein, Australia, Germany, France, and the Netherlands.  The factors that make the Rhine River the “Industrial Heartland” include that it encompassed the major empires, enabled trade and economic growth, linked European countries together and it is the most efficient way to transport people and goods. The physical body of water also enabled industrialization to occur more effectively.

The industrial heartland of North America is the Rust Belt; it is the region straddling the upper Northeastern United States, the Great Lakes, and the Midwest States. It is surrounded by water causing it to be a suitable area for trade and for the growth of the economy.  The Great Lakes and nearby Appalachia were utilized for transportation and natural resources. This enabled thriving coal and steel industries.

There are many impacts that human activity has had on the Rhine River basin. Farmland or buildings have replaced the Rhine’s riverside marsh and floodplain, which was used to hold back floodwater. Improved flood protection measures upstream cause the floodwater to move downstream more quickly than it used to. The river has been involved in a straightening process due to improved navigation for shipping; meaning the distance has been reduced, so this means that water moves downstream more quickly. Urbanization in the Rhine catchment area has also helped flooding due to the fact that the concrete and tarmac send more water to the river than the fields they replaced. The upper Rhine is used for generating hydroelectric power. These are all human causes on the Rhine River.

Reincorporating vegetation into the surrounding areas of the river where meadows and fields used to be would be an aiding solution to the flooding issue of Rhine River. It would act as an infiltration system and absorb excess waters, however it would be difficult to implement by people as times are getting more industrialized and advanced and more natural land is being replaced by buildings instead of the other way around. Reinforcing earth dykes with steel piling with stone blocks to reduce erosion is another solution that could be difficulty implementing as it would be costly, tedious and time consuming enhancing every dyke with steel however it would be worth it in the long run. Limiting residential development in areas where flood risks are likely is another solution to prolonging the longevity of people in this country however the houses in this area are most likely cheaper and more affordable for families that cannot support the expenses of another house therefore stopping people from living in these areas could end up putting people on the streets and killing them anyway. Allowing the river to flow back through marshland areas which had been previously been sealed off for navigation purposes would create a much further journey for the river to flow, lessening the intensity and speed of flooding however it would be inconvenient for travelers and shipping purposes as the journey would be much longer than if the river took a shorter route.