ESS 424 Stormwater exam 2 exam questions fully solved & updated 2024

- Absorb raindrop impact - Absorb flow impact energy - Slow runoff velocity - Reduce runoff amounts - Increase soils resistance to erosion 5 ways of controlling hillslope detachment - Vegetation - Straw mulch - Other mulch Materials - Rolled erosion control practices - Hydro Apllications types of materials that absorb raindrop impact - Inhibits rill formation because it forces the flow to spread out. - Causes the flow to change direction which prevents rill formation by way of spreading water out and preventing it from concentrating. If I protect the soil surface from flow turbulence impact, what effects does that generally have on rill formation? - Less energy in turbulent eddies - Gives runoff for time to infiltrate - Spread out flow further What are the things that slowing the flow does to reduce hillslope detachment? - Dramatic exposure of the soil allows rough pockets to be smoothed out more quickly such as tillage - When soil aggregates are broken up to create disturbed, rough soil such as tillage, the particles are more easily dethatched and can be transported away easier, causing roughness to diminish over time as particles are moved away - Disaggregation and straw that can be put down can move What factors cause diminution of the soil roughness over time? Vegetation won't slow down the flow of water if it does not move through it. Under what condition might lots of vegetation not really slow down the flow? Man made "Levels" around a hillslope that connect the same levels of elevation made to reduce soil erosion and surface runoff Describe "contour tillage" You are responsible for it Complete the following phrase: "If you concentrate the flow...." - Good organic matter is key - Soils resistance to erosion is a function of soil texture ( sand, silt, clay ) and soil particle aggragation. What is the key to strong soil aggregates? helps infiltration and well as hold soil in place on the hillslope: acts anchoring In what ways do subsurface vegetative material (e.g., roots) help stop hillslope detachment? Protecting the soil resource itself from degradation, eroded sediment can fill in erosion control devices such as sediment basins and channels. Besides protecting water quality, what are other goals of urban erosion and sediment control? Ensuring the sediment doesn't transport off site What is the primary concern for urban erosion and sediment control generally limited to while construction is in process? 14 days Vegetation on construction sites should be removed no more than how many days before earth-moving begins? - Compost is heavier than other mulches - Absorb water, causing it to become heavier - Nourishes soil What are the benefits of compost compared to other mulches? - The effectiveness of RECP is only as good as its level of direct contact with soil What is the critical element when using RECPs on construction sites? - Minimize runoff - Slow runoff by increasing roughness or forcing water into a ponded volume How do we usually stop sediment delivery from hillslopes? Insuring they are installed into the ground ( installed correctly, contouring, Eyelid shape ) What are the two key elements for the use of permeable barriers? Why is it important that buffer strips slow and spread the flow? - Slower water means more time for infiltration - As we slow down the flow the water wants to spread back out which helps inhibit the formation of rills - If water is not moving as fast, there is not much energy in the water that could detach particles Why is it important that buffer strips slow and spread the flow? - Grass waterways at the edge of the field at the lowest ultimate spot in the topography. Some kind of conveyance that ties in with other areas were we have collected and slowed down the water on a slope so that they are called slope drains. - The idea is collecting water at the top and provide some means to safely get it down to the bottom so that the slope is protected and excess water is avoided How does a "graded terrace" get its collected water off the field? - Big area with large amount of vegetation removed, we have to look at what is associated with sediment itself and what kind of damage can it cause, ( pyrite ) contributes to excess acidity and lower pH in the aquatic environment due to acid mine drainage from pyrite. - Mining reclaim sites have to contend with all of the extra acidity so it leads to heavily limed soils with 100% base saturation from the liming Why are specifically some of the problems with mining operations with respect to erosion control? FeS2 or pyrite Acidic mine spoils materials and drainage result from exposure to water and air of rock containing what? Roadways in urban settings do not contain vegetation, they are heavily trafficked, and water is able to move over forest roadways with a lot of erosional power. Why the emphasis on roads in controlling forest erosion and sediment? Some material, such as a log, placed diagonally across the road to funnel water down into a small trench beside the road so it doesn't skip over the roadways. What are "water bars" in forest erosion and sediment control? Because of the methane production from landfills when garbage decomposes. Why is stopping erosion so critical for landfills? - Minimize runoff - Slow runoff - Making the soil less erodible What are the three ways that we minimize the amount of sediment we must try to remove leaving our disturbed area? We want the sediment to settle before the water exits The goal of using a sediment basin is to have the sediment do what before the water leaves? The width The minimum area based on our design sediment diameter (Ad,min)depends on what? RLW,d = 10 when there is 100% effectiveness The General Overflow approach says that