Soil erosion is the movement of soil particles from one place to another under the influence of water or wind. We should care about erosion because: Erosion can be a major source of sediment that fills up ditches and clogs storm drainage pipes, which can in turn cause higher and more frequent localized flooding, and flooding is very dangerous for human, plants, animals, constructions, etc.
Principle of Watershed Management-WR304 Lecture #8 Lecturer: Bui Xuan Dung Small Quiz Name : Nguyen Huu Dung Student ID : 1353091031 (1) Why should we care about soil erosion? Answer : - Soil erosion is the movement of soil particles from one place to another under the influence of water or wind We should care about erosion because: - Erosion can be a major source of sediment that fills up ditches and clogs storm drainage pipes, which can in turn cause higher and more frequent localized flooding, and flooding is very dangerous for human, plants, animals, constructions, etc - Erosion constitutes one of the most significant global environmental problems we face today Water and wind erosion are now the two primary causes of land degradation The loss of soil fertility due to erosion is further problematic because the response is often to apply chemical fertilizers, which leads to further water and soil pollution, rather than to allow the land to regenerate Soil erosion (especially from agricultural activity) is considered to be the leading global cause of diffuse water pollution, due to the effects of the excess sediments flowing into the world's waterways Another ways with water quality which directly impacts on human life, animals, plants,etc - Soil particles picked up during wind erosion of soil are a major source of air pollution Dust from erosion acts to suppress rainfall and changes the sky color from blue to white, which leads to an increase in red sunsets - Moreover the effect of increased sediments loads on aquatic ecosystems can be catastrophic Silt can smother the spawning beds of fish, by filling in the space between gravel on the stream bed It also reduces their food supply, and causes major respiratory issues for them as sediment enters their gills - Erosion can have a negative impact on farmers, when they lose valuable soil and nutrients, which over time can result in lower crop yields - The negative impacts can also affect other property owners, when they lose soil and nutrients that are important to the health of their lawns, trees, and shrubs - Soil erosion negatively impacts on soil durability, it able to lead to be landslide with hill slope in rain season (2) We are currently working on soil management project in a 12,000 Watershed The area is covered by 30 % ground cover of grass with 25 % canopy of tall weed Based on the previous studies in the area, the following values were determined, – – – – R = 400 K = 0.15 LS = 10 VM = 0.13 Estimated annual Soil loss, A = R× K×LS×VM = 78 Total Erosion rate of the entire watershed = A x S = 78 × 12,000 = 936000 t/ha/yr (3) Now we are conducting watershed rehabilitation projects We converted vegetation ground cover as the following ½ watershed area (Area I) = 25 % tree canopy with a 60 % grass cover ½ watershed area (Area II) = 25 % short brush cover with 80 % grass cover Use the attached Table 7.5 for estimating VM factors Estimated annual soil loss of Area I, A1 = R× K×LS×VM1 = 24.6 t/ha/yr R× K×LS×VM2 = 7.2 t/ha/yr (VM1 = 0.041) Estimated annual soil loss of Area II, A2 (VM2 = 0.012) = Estimated total erosion of the entire watershed after rehabilitation (A1 × S1) + (A2 × S2) = (24.6 × 6000) + (7.2 × 6000) = 190800 t/yr Then estimate percentage of soil loss reduction after the rehabilitation management % (4) In the case of (2), you find that soil loss increases? Or decreases? You now explain why the changes occur after the watershed rehabilitation projects The reasons and processes for inducing such changes Answer: - Soil loss decreases The change occur after the watershed rehabilitation projects because: Vegetation is the key for controlling erosion: producing interception, ET reduces soil moisture, litter and OM, roughness, soil structure & infiltration Root system helps to increase infiltration rate, organic matters, hold soil and trash, it reduces overland flow and then less sediment comes to stream Moreover, understory vegetation help to decrease force of raindrop in detachment process, so soil will not be broken, it reduces sediment by sheet wash Ground cover also absorbs water to the soil and stop splash erosion Other finding that root system of vegetation can hold soil better and increased interception flow from stem flow, infiltration and others From that, we conclude that vegetation reduce soil erosion by many way direct and indirect ... process, so soil will not be broken, it reduces sediment by sheet wash Ground cover also absorbs water to the soil and stop splash erosion Other finding that root system of vegetation can hold soil. .. Answer: - Soil loss decreases The change occur after the watershed rehabilitation projects because: Vegetation is the key for controlling erosion: producing interception, ET reduces soil moisture,... Estimated annual soil loss of Area I, A1 = R× K×LS×VM1 = 24.6 t/ha/yr R× K×LS×VM2 = 7.2 t/ha/yr (VM1 = 0.041) Estimated annual soil loss of Area II, A2 (VM2 = 0.012) = Estimated total erosion of the