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HYDRO SUMMER > run off analysis > Flashcards

run off analysis Flashcards

1
Q

means the draining or flowing off of precipitation from a catchment area through a surface channel. It thus represents the output from the catchment in a given unit of time.

A

runoff

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2
Q

It is the part of the runoff which enters the stream immediately after the rainfall. It includes surface runoff, prompt interflow and rainfall on the surface of the stream.

A

direct runoff

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3
Q

The delayed flow that reaches a stream essentially as groundwater flow

A

baseflow

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4
Q

Runoff representing the response of a catchment to precipitation reflects the integrated effects of a wide range of catchment, climate and rainfall characteristics.

A

natural flow

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5
Q

are mathematical equations whose free parameters we have to specify by a given set of experimental data about a particular state to obtain formulas for predicting other data about this state

A

empirical formulas

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6
Q

are widely used in hydrology to provide quick reference information for estimating various hydrological parameters.

A

empirical tables

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7
Q

are graphical representations that depict the relationship between two or more hydrological parameters.

A

empirical curves

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8
Q

proposed one of the first relationships for t, the time of concentration in hours

A

Johnstone and Cross (US, 1949)

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9
Q

was the first to develop a synthetic UH based on a study of watersheds in the Appalachian Highlands. In basins ranging from 10 to 10,000 mi2

A

Snyder’s Method

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10
Q

Dominant Methods of flood estimation in the Philippines

A
  1. Hydrometeorological
  2. Flood frequency method
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11
Q

Factors Affecting Runoff

A

I. Storm Characteristics
II. Meteorological Characteristics
III. Basin Characteristics
IV. Storage Characteristics

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12
Q

Also known as “Precipitation Characteristics”.

A

Storm Characteristics

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13
Q

Storm Characteristics

A

a. Type or nature of storm and season
b. Intensity
c. Duration
d. Areal extent
e. Frequency
f. Antecedent Precipitation
g. Direction of storm movementStorm Characteristics

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14
Q

II. Meteorological Characteristics

A

a. Temperature
b. Humidity
c. Wind Velocity
d. Pressure Variation

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15
Q

III. Basin Characteristics

A

a. Size
b. Shape
c. Slope
d. Altitude or Elevation
e. Topography
f. Geology (Type of Soil)
g. Land use/Vegetation
h. Orientation
i. Type of Drainage net
j. Proximity to Ocean and Mountain
k. Ranges

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16
Q

Two Types of Catchments

A
  1. Fan Shaped Catchment
  2. Fern Leaf Catchment
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17
Q

IV. Storage Characteristics

A

a. Depressions
b. Pools and Ponds/Lakes
c. Stream
d. Channels
e. Check Dams
f. Upstream Reservoir/ Tanks
g. Food plains, Swamps
h. Groundwater storage in previous deposits (Aquifers)

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18
Q

Runoff Estimation Methods

A

a. Empirical Formula, Curves and Table
b. Infiltration Method
c. Rational Method
d. Overland Flow Hydrograph
e. Unit Hydrograph Method

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19
Q

is that balance of rain water, which flows or runs over the natural ground surface after losses by evaporation, interception and infiltration.

A

Runoff

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20
Q

The _______ of a catchment (usually means yield) is the net quantity of water available for storage, after all losses, for the purposes of water resources utilization and planning, like irrigation, water supply, etc.

A

yield

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21
Q

is the discharge in times of flooding of the catchment area, when the intensity of rainfall is greatest and the condition of the catchment regarding humidity is also favorable for an appreciable runoff.

A

Maximum flood discharge

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22
Q

is the movement of water from the soil surface into the soil. As long as the rate of water addition to the soil is slower than the rate of infiltration, water will move into the soil, and there will be no runoff.

A

Infiltration

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23
Q

Depending on how saturated the ground is, the water can continue downwards to replenish water tables and aquifers.

A

percolation

24
Q

showed that when the rainfall rate i exceeds the infiltration rate f, water infiltrates the surface soils at a rate that generally decreases with time

A

Horton (1933)

25
Q

One of the most commonly used procedures for calculating peak flows from small drainages less than 200 acres. This method is most accurate for runoff estimates from small drainages with large amounts of impervious area. Examples are housing developments, industrial areas, parking lots, etc.

A

rational method

26
Q

Limitations and assumptions in the Rational Method

A

• The drainage area should not be larger than 200 acres.
• The peak flow is assumed to occur when the entire watershed is contributing to runoff.

27
Q

is that water which travels over the ground surface to a channel. occurs as a thin sheet of water over the ground surface (soon after a storm starts), joins a stream channel, and then flows in the channel to the concentration point. is essentially a uniform flow over the surface as developed by C.F. Izzard (1948).

A

Overland Flow or Surface Runoff

28
Q

clay is hard to pick up due to cohesion

A

true

29
Q

sand is hard to pick up due to size

A

true

30
Q

• Water begins to collect near the top of the slope

A

Formation of Rills

31
Q

is a geographical feature that includes a shallow channel that is common on sloping grounds, like hillslopes. Rills are typically around 0.3 m deep and wide and are typically curvy in shape.

A

Gully Formations

32
Q

is a landform sunken or depressed below the surrounding area. form by various mechanisms.

A

nick or depression forms

33
Q

The headwall of a glacial cirque is its highest cliff. The term has been more broadly used to describe similar geomorphic features of non-glacial origin consisting of a concave depression with convergent slopes typically of 65 percent or greater forming the upper end of a drainage valley.

A

true

34
Q

referred to as Re, is used to determine whether the fluid flow is laminar or turbulent. The dimensionless Reynolds number plays a prominent role in foreseeing the patterns in a fluid’s behavior. It is one of the main controlling parameters in all viscous flows where a numerical model is selected according to pre-calculated Reynolds number.

A

reynolds number

35
Q

Basin outflow resulting from one unit of direct runoff generated uniformly over the drainage area ay a uniform rainfall rate during a specified period of rainfall duration

A

unit hydrograph method

36
Q

Three Types of Hydrographs:

A

flood
direct-runoff
unit

37
Q

graphs that show how a drainage basin responds to a period of rainfall

A
  1. Flood Hydrograph
38
Q

obstructions and losses are deducted but the results of excess precipitation do not equal to 1 inch.

A
  1. Direct Runoff Hydrograph.
39
Q

results in 1 inch of excess precipitation.

A
  1. Unit Hydrograph
40
Q

one method to develop hydrograph.

A

Linear Superposition Method

41
Q

Three Obstructions

A
  1. Interception from trees or vegetation
  2. Infiltration
  3. Detention storage
42
Q

precipitation that does not reach the soil, but is instead intercepted by the leaves, branches of plants and the forest floor

A
  1. Interception from trees or vegetation
43
Q

the flow of water from aboveground into the subsurface

A
  1. Infiltration
44
Q

the volume of water temporarily lying upon a watershed surface

A
  1. Detention storage
45
Q

Time parameters of a Unit Hydrograph

A

 Duration, (D)
 Lag Time, (Tp)
 Time of Rise, (Tr)
 Time of Concentration, (Tc)
 Time Base, (Tb)

46
Q

the time from start to finish of rainfall excess.

A

 Duration, (D)

47
Q

0the time from the center of mass rainfall excess to the peak of the hydrograph.

A

lag time, Tp

48
Q

the time from start to finish of rainfall excess to the peak of hydrograph

A

time of rise, Tr

49
Q

the time from the end of net rainfall to the inflection point of the hydrograph.

A

time of concentration, Tc

50
Q

– the total duration of the Direct Runoff hydrograph

A

time base, Tb

51
Q

2% to 10%

A

rolling

52
Q

greater than 10%

A

hilly

53
Q

Cf

A

10 yrs or less (1.0)
25 yrs (1.1)
50 yrs (1.2)
100 yrs (1.25)

54
Q

re < 1000

A

laminar flow

55
Q

re > 1000

A

turbulent flow

56
Q

re = 1000

A

transition region flow

HYDRO SUMMER (8 decks)

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