PART 2: SWC Engineering Flashcards
application of engineering and biological principles to the solution of soil and water management problems
Soil and Water Conservation Engineering
utilization of resources without or minimal waste
Conservation
maintaining the quality unchanged
Preservation
two most important natural resources where nature and agricultural production rely on
Soil (land) and water
Uses of water: AADIPRe
- agricultural production
- aquaculture
- domestic
- industrial/commercial
- power supply
- recreation
Sources of water: PSBG
- precipitation
- surface of water
- bodies of water
- groundwater
Total land area of the PH
300,000 km2 or 30,000,000 has
NIA estimate
- 1/3 of land is ____ potential for irrigation
arable
BSWM
Bureau of Soil and Water Management
under DA, implements projects; development of small-scale irrigation projects
Bureau of Soil and Water Management
are those with slope of less or equal to 18% and which could have applicability and effective use of agricultural machineries for production
arable land
are those non-alienable land
non-arable lands
in-charge in large irrigation projects
NIA
World Bank estimated _____ of arable land.
4.6M hectare
____ were provided with irrigation facilities which translate to 39.13% irrigation efficiency.
1.2M has
Factors Affecting Productivity of Land and Water Resources: PLCLP
- Poverty
- Land Tenure
- Conversion of arable land to other uses
- Lack of appropriate technology for conservation processes
- Political will of government to enforce and/or implement policies on conservation
is the detachment and transport of soil particles by natural or anthropogenic causes
soil erosion
the susceptibility of the soil to be eroded
soil erodibility
the capacity of rainfall to cause erosion
rainfall erosivity
eroding agents
rainfall/raindrop, runoff, wind
Environmental impacts of soil erosion
on-site impacts
off-site impacts
ON-SITE IMPACTS (RRIDID)
- Reduce crop productivity due to loss of topsoil
- Reduced infiltration rate, percolation, and subsurface/aquifer recharge
- Increased direct runoff
- Decreased land value
- Increased local temperature
- Damaged biodiversity (flora and fauna)
OFF-SITE IMPACTS (SRFDD)
- Situation in farms, rivers, etc., and other water channels and water control and detention structures
- Reduced water capacity of rivers, water channels, and dams…
- Flooding of downstream
- Decreased water supply (fresh)
- Damaged biodiversity
Forms of Classification of Erosion based on nature of occurrence (NM)
- natural or geologic erosion
- man-made or accelerated erosion
Forms of Classification of Erosion based on relative place of occurrence (SuSub)
surface erosion
subsurface erosion
Forms of Classification of Erosion based on eroding agent (WaWi)
water erosion (rainfall e., runoff e.)
wind erosion
Forms of Classification of Erosion based on sequential occurrence (SIRGS)
sheet erosion
interill erosion
rill erosion
gully erosion
streambank erosion
is the uniform removal of soil in thin layers from sloping land, resulting from sheet or overland flow
sheet erosion
is splash and sheet erosion combined
interill erosion
is the detachment of soil by a concentrated flow of water
rill erosion
produces channels larger than rills called gullies, and which cannot be obliterated by normal tillage
gully erosion
consists of soil removal from stream banks or soil movement in channel
streambank erosion
mechanics of soil erosion
Rainfall erosion
Runoff or scour erosion
Gully erosion
includes detachment (by impact) & transport of soil by raindrop
rainfall erosion
Factors affecting the detachment and transport of soil particles by raindrops (CSTV)
Climatic factors
Soil Characteristics
Topography
Vegetation and Plant Cover
rainfall characteristics (DIDT)
Drop size and size distribution
Intensity
Duration
Terminal Velocity
quantifies the erosivity pf raindrops
terminal velocity
Climatic factors
rainfall characteristics
wind
Soil Characteristics (TSOSC)
Texture
Structure
Organic matter content
Soil moisture content
Compactness (porosity)
higher OM, _____
lower soil erosion
Topography (SgSl)
Slope gradient
Slope length
includes detachment (by scouring) and transport of soil
runoff or scour erosion
factors affecting the detachment and transport of soil particles by runoff
rainfall characteristics
soil characteristics and geology
rainfall characteristics
intensity
duration
topography
vegetation
conservation practices
presence of depression
channel geometry
soil characteristics and geology (TSIO)
texture
structure
initial MC
organic matter
bigger than rills and cannot be obliterated by ordinary tillage
gully erosion
classification of gully based on size: small
depth: < or eq to 1 m
drainage area: < or eq to 2 ha
classification of gully based on size: medium
depth: 1-5 m
drainage area: 2-20 ha
classification of gully based on size: large
depth: >5 m
drainage area: ?20 ha
classification of gully based on channel slope
V and U-shaped
classification of gully based on morphology (LBDTPC)
Linear
Bulbons
Dendritic
Trellis
Parallel
Compound
stage of gully development
- channel erosion by downward scour of the top soil
- upward movement of gully head and enlargement of the gully width
- healing stage
- stabilization stage
rate of topsoil formation
25 mm of soil every 30 years
factors considered in determining soil erosion limit
- rate of topsoil formation
- thickness
- parent material
- productivity level of soil
- previous rate of soil erosion
methods of soil erosion movement
- soil erosion plots
- rainfall simulator
- catchment-based or watershed-based method
soil erosion plots standard conditions
bare fallow, 9% slope, 72.6 ft length
SDR
Sediment Delivery Ratio
fraction of sheet and rill erosion that actually reaches the reference point of discharge
Sediment Delivery Ratio
USLE
Universal Soil Loss Equation
RUSLE
Revised Universal Soil Loss Equation
MUSLE
Modified Universal Soil Loss Equation
WEPP Model
Water Erosion Prediction Project
planting along contours or land surface with same elevation
contouring
alternate planting of 2 or more different crops along contours
stripcropping
placement of crop residues, plastic, or other synthetic materials around the base plant or throughout the field to reduce evaporation from land surface
mulching
retarding vegetation planted alternately with rows of crops, along contours
hedgerows and grass boundary
alternating planting of different crops on successive plating seasons
crop rotation
a minimum tillage practice in which the crop is sown directly into soil not tilled since the harvest of the previous crop
zero tillage/dribble planting
reduces velocity and increasing time for infiltration
terracing
types of terracing
- bench terrace
- forward-sloped terrace
- reverse-sloped terrace
- irrigation/basin terrace
- eyebrow or orchard terrace
impounding structures and reservoirs; reduce velocity and modulate volume of water; SWIPs AND EBERTING
runoff storage or detention structure
engineering and mechanical method used for gullies, streams, and other water channels; use of grassed waterways
protected waterways
structure across a stream to control or divert the flow; device for measuring the flow of water
weir
water conveyance and control structure with a considerable slope, conveying water from a higher to a lower elevation
chute
water conveyance and control structure with a 90 degree water drop
drop spillway
water conveyance and control structure with water inlet mechanism
drop inlet
cut-offs and detour channels
diversion channels
is a natural or artificial channel that shortens a meandering stream
cut-offs
is a synthetic permeable textile material used with soil, rock, or any other geotechnical engineering related material
geotextile
also called geosynthetics that is an effective erosion control and can be used together with rock or other riprap material and placed along a streambank
geotextiles
developed by Wischmeier in 1962 and his associates and has been widely accepted as a means of assessing long-term average soil loss
Universal Soil Loss Equation (USLE)
In this equation, daily precipitation data were used for estimating rainfall erosivity indices
Modified Soil Loss Equation (MUSLE)
an improved version of the USLE for predicting sheet and rill erosion
Revised Universal Soil Loss Equation (RUSLE)
is a process-based, distributed parameter, continuous computer simulation model designed for predicting water-induced soil erosion either on a hillslope or watershed-scale
WEPP Model (Water Erosion Prediction Project)
entrainment of solid material into a water body or channel and its further effects and consequences
sediment transport
process of deposition of sediment to downstream location
sedimentation
rate of sediment flow (mass/time, i.e. kg/s)
sediment load or discharge
total mass of sediment, usually expressed per year
sediment yield
sediment or soil particle suspended in the water body and has more harmful effect due to its higher transportability
suspended load
sediment near or few inches from the stream bed and move by crawling or sliding
bed load
sediment transported by saltation or jumping
saltation
suspended and saltation load
wash load
the percentage of incoming sediment retained in the reservoir
trap efficiency
is a conduit in which a liquid flows with a free surface
open channel
flow having a free surface and subjected to atmospheric pressure
open channel flow
flow confined in a closed conduit, has no free surface and exerts no direct pressure but hydraulic pressure only
pipe flow
if the depth of flow does not change pr it can be assumed to be constant during the time interval under consideration
steady flow
for steady flow, the discharge is ____ throughout the reach of the channel under consideration, thus, the flow is _____
constant, continuous
if the depth changes with time
unsteady flow
if the depth of flow is the same at every section of the channel
steady uniform flow
if the depth of flow changes along the length of the channel
varied/non-uniform flow
water runs in or out along the course of flow
spatially varied or discontinuous flow
together with gravity, they are the factor that basically affect open channel flow
viscosity
water particles appear to move in definite smooth paths or streamlines; and infinitesimally thin layers of fluid slide over adjacent layers
laminar
viscous forces are weak relative to inertial forces
turbulent
R<500
laminar flow
R>2000
Turbulent flow
500<R>2000</R>
Transitional flow
usually a long and mild-sloped channel built in the ground which maybe lined or unlined
canal
include all watercourses that exist naturally on the earth
natural
those constructed or developed by human
artificial
lining of this maybe stone masonry, concrete, or wood
canal
is a channel made of wood, metal, or concrete supported above the surface of the ground to carry water across a depression
flume
channel having a steep slope
chute
similar to chute, but the change in elevation is effected in a short distance
drop
a covered channel of comparatively short length installed to drain water through a highway and railroad embankments
culvert
comparatively long covered channel used to carry water through a hill or any obstruction on the ground
open-channel tunnel
water is brought from streams or reservoirs to storage ponds or tanks or directly to the irrigated land
irrigation
low-lying, swampy, or waterlogged lands are made productive by draining them through open ditches or by laying and covering pipe which may or not flow full
drainage
protection of residential areas and valuable lands from floods often requires improving a natural channel by straightening….
flood control
water is brought from stream or storage reservoirs to ponds
domestic water supply
water is brought from streams to headworks above power plants
waterpower development
usually are covered conduits or pipes; are not supposed to flow
sewerage
a channel built with uniform cross-section and constant bottom slope
prismatic channel
is the vertical distance of the lowest point of a channel section from the free surface
depth of flow (y)
is the elevation or vertical distance of the free surface above a datum
stage
is the width of the channel section at the free surface
top width
is the cross-sectional area of the flow normal to the direction of flow
water area
the length of the line of intersection of the channel wetted surface with a cross-sectional plane normal to the direction of flow
wetted perimeter
ratio of water area to its wetted perimeter
hydraulic radius
R=A/P
ratio of the water area to the top width
hydraulic depth
D=A/T
the flow specific energy is minimum for a given discharge and the discharge is maximum for a given specific energy
the critical flow
Presented in 1889 by Irish engineer Robert Manning. It is the formula generally used in open channel conditions
manning’s formula
these are lined and built-up channels which can withstand erosion satisfactorily
non-erodible chanel
purpose of lining the channel
- to prevent erosion
- to check seepage losses
it is the velocity that will not start sedimentation and will not induce the growth of aquatic plants and moss
minimum permissible velocity/non-silting velocity
The side slope of a channel depends mainly on the kind of material. Other factors to be considered include,
- method of construction
- condition of seepage loss
- climatic change
- channel size
the vertical distance from the top of the channel to the water at the design condition
prevent waves or fluctuations in water surface
freeboard
it is the channel section having the least wetted perimeter for a given area and maximum conveyance
best hydraulic section
the greatest mean velocity that will not cause erosion of the channel body
maximum permissible velocity method
the pull of water on the wetted area
tractive force
in uniform flow, this is equal to the effective component of the gravity force acting on the body of water, parallel to the channel bottom
tractive force
the average tractive force per unit wetted area
unit tractive force
the manning coefficient of roughness for grassed channels
retardance coefficient
the total land area that contributes to the flow of a particular water body and drains to a common outlet
watershed
is the divide between two areas drained by different river systems
watershed
are the natural drainage areas within the boundary defined by the watershed divide
catchments and basins
are essentially the same, but basin is most often used to describe a region drained by a large river system
watershed and catchments
the process of guiding and organizing land and other resources uses in a watershed to provide desired goods and services without adversely affecting soil and water resources
watershed management
ideally an approach where the strategy is to prevent watershed resource degradation from occuring
prevention
as a rule, land use management practices are strongly influenced by the
an inundation or overflow from river or other bodies of water
excess amount of water or water level in a stream channel above its capacity
flood
low lying areas which are frequently flooded
flood plain
refers to the reduction of flood hazards and the ensuing damage to any given region of a flood plain to a minimum, consistent to the cost involved
flood protection/flood damage mitigation
the distinction between normal discharge and flood-flow is generally determined by ____
the stage of the steam when bankful
floods that occur form storms of low intensity having a duration of a few days to several weeks
large-area floods
floods that occur from storms of high intensity having a duration of 1 day or less
small-area floods
works concerning the improvement of channel/stream cross-section, alignment, longitudinal slope, and roughness, thus, increasing velocity
stream training and regulation
flood routing to storage or detention reservoir
reduction of peak discharge
storage confinement for other water use
storage reservoir (dam)
structure or provision to reduces the peak discharge of flood by temporarily delaying the flow and reducing the velocity
detention reservoir
use of a pre-determined channel
confinement of the flood plain
diversion of excess water through flood by-pass and back to the stream or to another channel catchment
flood wave attenuation
include vegetation management, and soil and water conservation structures
land management
mapping of flood-prone areas with probability of flood levels
flood plain zoning and managament
includes all measures that will reduce flood flows in watershed of small rivers and their tributaries
headwater flood control
measures that reduces the impacts of flood in the outlets and lower the reaches of the watershed
downstream flood control
include those that affect the channel itself and those that reduce sediment from upper tributaries
preventive maintenance
is the process of determining the stage height, storage volume, and outflow rate from a reservoir
flood routing
operates automatically by discharging through one or more fixed openings in the dam
detention reservoir
the percentage of incoming sediment retained in the reservoir
trap efficiency
are embarkments along streams or on flood plains designed to confine the river flow to a definite width for the protection of surrounding land from overflow
levees
sometimes referred to as jetties, serve to decrease the velocity along the concave bank to the protect the bank, thereby reducing deposition below
retards
these are measures of prevent stream bank erosion
vegetative or mechanical control
is the process of determining the stage height, storage volume, and outflow from a reservoir or a stream reach for a particular inflow hydrograph
flood routing
same as runoff hydrographs
inflow hydrographs
represents the depth-discharge relation of the reservoir spillway structure or the lower end of a stream reach
outflow hydrograph
represents the depth-capacity relation pf a reservoir above the elevation of some arbitrarily selected stage
available storage
shows the rate of outflow (spillway discharge) as a function of time
outflow hydrograph
is designed to carry all the frequent discharges
principal spillway
is usually an open channel and is designed to operate for a short time during which flood flows exceed the capacity of the other spillways
flood spillway
another factor of safety, is always provided to prevent waves or any other water from overtopping the dam
freeboard
