Lecture 10 - Flood Concepts and Hydrological Models Flashcards
What are flood maps used to identify?
areas that could be affected by floods (floodplains)
What kinds of flood maps can be produced?
flood hazard maps, flood risk maps
What areas do flood hazard maps identify?
areas tha would be affected (flooded) by events of different return periods (ex 1:100 yr flood)
What timeline do Nova Scotia flood mapping studies focus on?
1:100 and 1:20 year floodlines
Describe the 1:20 year floodline.
typically been termed the floodway, area that is more frequently flooded, conveys the majority of floodwaters and would have the greatest water depths and velocities
What is the zone between the 1:20 and 1:100 year floodines called?
flood fringe
What kind of different resriction would be applied to the 1:20 year and 1:100 year floodlines?
different land use restrictions
What do flood risk maps do?
identify vulnerable infrastructure and the potential consquences associated with specific flood events
What are the main three elements of a floodplain delineation study?
hydrology, hydraulics, mapping
What does the hydrology element of floodplain delineation study consist of?
predicted peak flows, frequency analysis, hydrological modeling
What does the hydraulics element of a floodplain delineation study consist of?
computed water surface profile at peak flows, steady vs unsteady state
What does the mapping element of a floodplain delineation study consist of?
floodplain extents, hazard zones, risk zones
What are additional factors that cause flooding?
ice jams, hydraulic structures like culverts (blockages) and bridges, confluence of rivers, tidal boundary conditions
What are the snowmelt contributions to flooding?
depth, density, snowwater equivalent (SWE), ablation
What are the two basis that hydrological models can have?
temporal basis, spatial basis
What are the things that can be evaluated on a temporal basis?
steady vs unsteady state, event vs continuous
Describe continuous hydrological models.
simulate both wet and dry hydrologic processes, wet processes include precipitation type, infiltration, runoff, dry processes include evapotranspiration, soil water redistribution, baseflow (interflow and shallow groundwater flow)
What types of hydrological models can happen on a spatial basis?
lumped, distributed, 1,2,3 dimensional
Describe a lumped hydrological model.
rainfall and properties averaged over basin, one rainfall/runoff model, prediction at only one point
Describe a distributed hydrological model.
rainfall and properties in each grid, rainfall/runoff model in each grid, prediction at many points
Describe a semi-distributed hydrological model.
watershed is classified into units of land that have similar hydrologic characteristics (Hydrologic Response Units (HRUs)), soil and water assessment tool (SWAT) is a semi-distributed model
What needs to be considered when designing or selecting a hydrologic model?
model purpose, required scale, required input data, model calibration and validation, software and hardware requirements
What is model calibration? Why do models have to be calibrated?
varying values of input parameters (optimization) so that model outputs match measured data and goodness of fit tests, becasue input parameters can’t be estimated by actual measurements
What is model validation?
testing calibrated model with an independent set of observed data that are different from those used in calibration, can take different forms like temporal or spatial validation
In what ways can model performance or goodness of fit be assessed?
graphical, statistics, water balance assessment
What are the widely used hydrological models?
HEC-HMS, SWMM, TR-55, HSPF, SWAT
Describe the HEC-HMS hydrological model.
event model that simulates hydrology, developed and supported by the US Army Corps of Engineers
Describe the SWMM hydrological model.
storm water management model, event model which simulates hydrology and water quality in urban areas, developed and supported by USEPA
Describe the TR-55 hydrological model.
event model that simulates hydrology, developed and supported by US Natural Resoruces Conservation Service (NRCS)
Describe the HSPF hydrological model.
hydrologic simulation program-fortran, continuous watershed model that simulates hydrology and water quality, supported by the United States Environmentla Protection Agency (USEPA)
Describe the SWAT hydrological model.
soil and water assessment tool, continous watershed model that simulates hydrology and water quality, supported by the USEPA and US Dept of Agriculture
