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The Natural Environment

The Natural Environment. The Hydrologic Cycle . Hydrologic Processes. Hydrologic Budget. Change in storage = inflow – outflow ∆S = P – R – G – E – T Where: P = Precipitation R = Surface Runoff G = Groundwater E = Evapotranspiration T = Transpiration

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The Natural Environment

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  1. The Natural Environment

  2. The Hydrologic Cycle

  3. Hydrologic Processes

  4. Hydrologic Budget • Change in storage = inflow – outflow • ∆S = P – R – G – E – T • Where: • P = Precipitation • R = Surface Runoff • G = Groundwater • E = Evapotranspiration • T = Transpiration • ∆S = Change in storage over specified time

  5. Aral Sea 1989 2008

  6. Watersheds • Area of land which drains to a single outlet point • Characterized by • Size, slope, shape, soil type, storage capacity, land use, channel morphology • Basin • Large watershed • i.e. Mississippi river basin

  7. Hydrology and Infrastructure • Design infrastructure to withstand precipitation of specific reoccurrence interval • 100yr = 1% chance • 10yr = 10% chance • Expense increases as you design to a less frequent return period • Location specific IDF curves relate rainfall intensity and duration to probability

  8. Rivers and Infrastructure • flood probabilities not directly related to storm probabilities • 100yr storm does not necessarily equate to 100yr flood • Floodplain • The land along a stream or river that is inundated when the stream overtops its banks • FEMA determines 100yr floodplain and updates it accordingly with increasing development • More impermeable surfaces = more runoff • Most building codes prohibit construction in the 100yr floodplain

  9. The Woodlands • Designed to handle 100yr flood by not altering the natural floodplain

  10. Geological Formations • Soil • Uppermost layer of unconsolidated material that lies above the uppermost layer of rock (consolidated material) • Soil type and location of bedrock have huge influence in construction • Borings used to design building foundation • Location of consolidated material varies even over a short distances

  11. Vertisolsand Houston

  12. Groundwater • Water which fills pores and fractures of unconsolidated material • Aquifer • Geologic formation that stores water • Supply in jeopardy as demand increases

  13. Aquifer Source: National Groundwater Association

  14. Porosity, Head and GW Flow Rates Darcy’s Law (1856) relates change in head and hydraulic conductivity to groundwater flow rates: dh/dL = change in head K = hydraulic conductivity = 10-2 cm/s (Sand) = 10-4 cm/s (Silt) = 10-7 cm/s (clay) Seepage velocity (actual flow) is Darcy’s velocity divided by the porosity of the groundwater medium: n = porosity Porosity = vol void / total vol

  15. Climate Change • Greenhouse Gases: • Trap heat radiating outward from Earth • Increase Earth’s temperature to support life • 30oC cooler w/o • Increasing concentrations amplify such warming • Five main greenhouse gases: • Water Vapor (H2O) .004 – 4% (40–40000ppm) • Carbon Dioxide (CO2) .0391% (391ppm) • Methane (CH4) .00017% (1.7ppm) • Nitrous Oxide (N2O) .000033% (.33ppm) • Ozone (O3) .000005%

  16. IPCC and Climate Change • Intergovernmental panel on climate change • International body for the assessment of climate change • Found that climate change is most likely anthropogenic • Kyoto protocol created as a result • Calls for 5% global reduction in greenhouse gas emissions • US assigned 7% reduction • US has not signed

  17. Kyoto Countries

  18. Climate Change Consequences • Increased drought and water shortages • Extinction • Coral reef loss • Alterations to carbon cycle • Loss of habitat • Changes in locations of agricultural regions • Increased flooding • Increased malnutrition and disease • Increased frequency and severity of storms

  19. Climate Change Consequences Downtown Boston 100 year floodplains: current (solid) After “high level” greenhouse gas emission scenario (dashed)

  20. Dealing With Climate Change Below: Global temperature profile with different GHG emission scenarios Above: IPCC projected global mean temperature change with different emission scenarios

  21. Engineering for Climate Change • Problem: • Predicting the extent of climate change is challenging • Two options: • 1. design for current day conditions and risk failure • 2. design for worst case scenario and risk extra expenditure • Solution: • Adaptive management • Incorporate future uncertainties into design plan so that if changes do occur, strategy is in place to handle them • E.g. Design levee to be readily modified to accommodate seawater increase

  22. Conclusion Infrastructure has impact on the environment and the environment impacts infrastructure Relationship must be understood for future sustainable development

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