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Hydrology > Lecture 10 > Flashcards

Lecture 10 Flashcards

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1
Q

flood maps are used to

A

identify areas that could be affected by floods (floodplains)

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2
Q

what are some types of floodplain maps

A

flood hazard maps
flood risk maps

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3
Q

flood hazard maps identify

A

areas that would be effected by events of different return periods

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4
Q

flood risk maps identify

A

vulnerable infrastructure and the potential consequences associated with specific flood events.

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5
Q

In nova scotia flood mapping studies have focused on

A

identifying the 1:00 and 1:20 year floodlines

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6
Q

the 1:20 year floodline is known as the

A

Floodway. This is the area that is more frequently
flooded, conveys the majority of floodwaters, and
would have the greatest water depths and velocities
* Different land use restrictions would be applied to the
1:20 and 1:100 yr floodlines

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7
Q

Elements of a Floodplain Delineation Study

A

Hydrology
* Predicted peak flows
* Frequency Analysis
* Hydrological
Modeling

Hydraulics
* Computed
water surface
profile at peak
flows
* Steady vs
Unsteady State

Mapping
* Floodplain
extents
* Hazard Zones
* Risk Zones

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8
Q

Elements of a Floodplain Delineation Study: hydrology

A
  • Predicted peak flows
  • Frequency Analysis
  • Hydrological
    Modeling
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9
Q

Elements of a Floodplain Delineation Study: hydraulics

A
  • Computed
    water surface
    profile at peak
    flows
  • Steady vs
    Unsteady State
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10
Q

Elements of a Floodplain Delineation Study: mapping

A
  • Floodplain
    extents
  • Hazard Zones
  • Risk Zones
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11
Q

Additional factors that cause flooding

A
  • Ice jams
  • Hydraulic structures
    – Culverts (blockages)
    – Bridges
  • Confluence of rivers
  • Tidal boundary
    conditions
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12
Q

Case Study: Sackville and Little Sackville Rivers
information

A
  • 150 km2 vs 15 km2
  • Primarily rural
    (Sackville) vs highly
    urbanized (Little
    Sackville)
  • Downstream
    boundary condition
    (Bedford Basin)

Developed maps of
* 1:20, 1:100. 1:500 and Probable Maximum
Precipitation floods
* Historical and future climate rainfall and sea level
rise
* Hydrologic model: PCSWMM
* Hydraulic model: PCSWMM and HEC RAS

Water Survey of
Canada
* Sackville River
* Little Sackville
River
* ECCC climate
stations (3)
* Dalhousie Centre for
Water Resources
Studies
* 6 additional
water level
monitoring
stations

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13
Q

Snowmelt Contributions

A
  • Depth
  • Density
  • Snowwater
    Equivalent (SWE)
  • Ablation
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14
Q

Empirical Snowmelt
Models

A

Empirical snowmelt models
take the form of TemperatureIndex Equations:
Δw = M (Ta – Tm) when Ta ≥ Tm
Δw = 0 when Ta < Tm

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15
Q

Types of Hydrological Models

A
  1. Temporal Basis
    * Steady vs Unsteady State
    * Event vs Continuous
  2. Spatial Basis
    * Lumped
    *Distributed
    * 1, 2, or 3 Dimensional
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16
Q

Continuous Models

A

Simulate both “Wet” and “Dry” hydrologic processes

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17
Q

Wet Processes

Study These Flashcards
A

*Precipitation type
* Infiltration
* Runoff

18
Q

Dry Processes

Study These Flashcards
A
  • Evapotranspiration
  • Soil water redistribution
  • Baseflow (interflow and shallow groundwater flow)
19
Q

lumped spatial model

Study These Flashcards
A

rainfall properties arranged over basin
one rainfall/runoff model
prediction at only one point

20
Q

distributed spatial model

Study These Flashcards
A

rainfall properties in each grid
rainfall/runoff model in each grid
prediction at many points

21
Q

Semi-Distributed Models

Study These Flashcards
A
  • Watershed is classified into units of land that have similar
    hydrologic characteristics (Hydrologic Response Units
    (HRUs))
  • The Soil and Water Assessment Tool (SWAT) is a SemiDistributed Model
22
Q

Some Things to Consider When Designing or
Selecting a Hydrologic Model

Study These Flashcards
A
  • What is the purpose of the model?
  • What scale is required?
  • What input data is required?
  • How will I calibrate and validate the model?
  • What are the software/hardware requirements to run simulations?
    Need to consider the catchment and conditions you are trying to model!
23
Q

The components of a hydrologic model

Study These Flashcards
A

depends on the catchment and characteristics you are trying to model

24
Q

Example Model Structure: HEC-HMS

Study These Flashcards
A

Event and continuous model developed by US
Army Corps of Engineers

25
Example Model Structure: HBV
Continuous hydrologic model developed by Swedish Meteorological and Hydrological Institute (SMHI) for each hydrologic response unit (HRU) Layer 1 and 2 (snow and melt water) Layer 3 (soil) Layer 4 (upper groundwater) Layer 5 (lower groundwater)
26
Many model input parameters cannot be estimated by actual measurements therefore
, in general, a model will have to be calibrated
27
Even if a parameter is measured
it is typically not at a scale that is compatible with the modeling scenario
28
what is calibration
varying values of input parameters (optimization) so that model outputs match measured data (model can be run dozens or hundreds of times to get an acceptable match) – goodness of fit tests
29
what is Model Validation
Testing calibrated model with an independent set of observed data that are different from those used in the calibration
30
two kinds of model validation
Temporal Validation (Split Sample) * Spatial Validation (Nested Watershed, Paired Watershed)
31
what ways can goodness of fit or model performance be assessed
* Graphical * Statistics * Water Balance Assessment
32
Widely Used Hydrological Models
HEC-HMS - Event model that simulates hydrology. Developed and supported by the US Army Corps of Engineers * SWMM – Storm Water Management Model. Event model which simulates hydrology and water quality in urban areas. Developed and supported by USEPA (Commercial versions include PCSWMM and XPSWMM) * TR-55 – Event model that simulates hydrology. Developed and supported by US Natural Resources Conservation Service (NRCS) * HSPF – Hydrologic Simulation Program-Fortran. Continuous watershed model that simulates hydrology and water quality. Supported by the United States Environmental Protection Agency (USEPA) * SWAT – Soil and Water Assessment Tool. Continuous watershed model that simulates hydrology and water quality. Supported by the USEPA and US Dept of Agricultur
33
* HEC-HMS -
Event model that simulates hydrology. Developed and supported by the US Army Corps of Engineers
34
* SWMM –
Storm Water Management Model. Event model which simulates hydrology and water quality in urban areas. Developed and supported by USEPA (Commercial versions include PCSWMM and XPSWMM)
35
TR-55 –
Event model that simulates hydrology. Developed and supported by US Natural Resources Conservation Service (NRCS)
36
* HSPF –
Hydrologic Simulation Program-Fortran. Continuous watershed model that simulates hydrology and water quality. Supported by the United States Environmental Protection Agency (USEPA)
37
SWAT –
Soil and Water Assessment Tool. Continuous watershed model that simulates hydrology and water quality. Supported by the USEPA and US Dept of Agriculture
38
Baker lake case study info
Using HEC-HMS to Simulate the Hydrology of a Arctic Watershed Impacted by Wastewater Effluent Water quality monitoring (Jun 2018 – Sept 2019) * Continuous flow measurements (Jun 2018 – Sept 2019) * Surveying bankfull channel geometry (Sept 2019) * Bathymetry studies (Sept 2019 Integrated Contaminant - Hydrological Transport Model * Frequency analysis: 2, 10, 25, & 100 -year return periods * Wetland Contaminant Fate and Transport Model
39
LID on groundwater case study info
Using PCSWMM to Assess Effects of Low Impact Development on Groundwater Availability In this case study LID implementation was predicted to have modest positive impacts on groundwater levels * However, the proposed development (without LID) was predicted to have only minor impacts on groundwater levels * LID effects would be more pronounced in different hydrogeologic environments or development scenarios
40
what is PCSWMM
* Commercial version of the EPA SWMM model * Urban hydrology and hydraulics * Event and Continuous modeling capabilities * Explicit simulation of Low Impact Development (LID) systems * Rain Gardens (Bioretention Systems) included on all residential lots

Hydrology (8 decks)

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