Water Resources Quiz #2 Questions &
Answers(RATED A)
what are urban stormwater-management systems designed to control? - ANSWERquality and
quantity of stormwater runoff
why do we need urban stormwater management systems? - ANSWERUrbanization increases runoff
and would inevitably lead to 1. increased flooding of downstream areas and 2. deterioration of the
quality of receiving waters
how do urban stormwater-management systems work? - ANSWERusing best management practices
(BMPs) and stormwater control measures (SCMs). Performance goals of SCMs are set by local
authority
When are urban stormwater-management systems used? - ANSWERAnytime a new land
development is being made or evaluating the performance of an existing system in a region
(Pittsburg case study)
HISTORY OF STORMWATER MANAGEMENT: WWII - ANSWERstormwater management sought to
evacuate water away from site as quickly as possible
HISTORY OF STORMWATER MANAGEMENT: 1970's - ANSWERdetention ponds; main goal is to reduce
amount of peak flows
HISTORY OF STORMWATER MANAGEMENT: more recently - ANSWERgreen infrastructure, low impact
development (LID).
what are the goals of green infrastructure and low impact development? - ANSWERreduce peak flow,
reduce volume of water, improve water quality, use sustainable materials and natural vegetation,
improve aesthetics
Quantity Control - ANSWERoPostdevelopment runoff peak flowrate less than or equal to the
predevelopment peak flowrate
oFor multiple rainfall events, depending on jurisdiction (i.e., 25-year, 24-hour duration rainfall event)
oSome regulations also look at the volume of flow
, Quality Control
Type 1: - ANSWERwater-quality rainfall depth, determined from an analysis of local rainfall conditions
and data (i.e., 90th percentile depth). This yields a water quality volume (WQV), the runoff
corresponding to that event
Quality Control Type 2: - ANSWERspecify a fixed water quality volume regardless of catchment
characteristics.
o Idea is that most pollutants in runoff are contained in the first flush
o But! As imperviousness increases, runoff increases and thus the volume of water in the first flush
would increase
Quality Control Type 3: - ANSWERremove a minimum fraction of the annual-average load of specified
pollutants to be removed from runoff prior to discharge. Required removal is the removal efficiency.
Green techniques examples: - ANSWERHouses: use different strategies to collect, infiltrate and
cleanse rainwater ( splashblocks, rocks, furrows or channels, stormwater popups, planted
depressions, yard drains)
Streets: slope to one side and cut in curb direct rainwater into planted and grass sections
Swales: collect, absorb, and filter rainwater from streets and houses into the ground before going
into the city storm drain
Conveyance furrows: direct water away from the house via a path of gravel and crushed rock
Bioswales - ANSWERused as a means of both conveying water and also removing pollutants
Impoundments - ANSWERdepressed storage areas that collect surface runoff and release it at a
reduced rate
Detention basins - ANSWERstorage areas where stored water is released gradually, often used in
cases with minimal infiltration (dry most of the time)
detention basins advantages: - ANSWERmay be cheaper to implement due to having a smaller size,
may be required by regulations
Answers(RATED A)
what are urban stormwater-management systems designed to control? - ANSWERquality and
quantity of stormwater runoff
why do we need urban stormwater management systems? - ANSWERUrbanization increases runoff
and would inevitably lead to 1. increased flooding of downstream areas and 2. deterioration of the
quality of receiving waters
how do urban stormwater-management systems work? - ANSWERusing best management practices
(BMPs) and stormwater control measures (SCMs). Performance goals of SCMs are set by local
authority
When are urban stormwater-management systems used? - ANSWERAnytime a new land
development is being made or evaluating the performance of an existing system in a region
(Pittsburg case study)
HISTORY OF STORMWATER MANAGEMENT: WWII - ANSWERstormwater management sought to
evacuate water away from site as quickly as possible
HISTORY OF STORMWATER MANAGEMENT: 1970's - ANSWERdetention ponds; main goal is to reduce
amount of peak flows
HISTORY OF STORMWATER MANAGEMENT: more recently - ANSWERgreen infrastructure, low impact
development (LID).
what are the goals of green infrastructure and low impact development? - ANSWERreduce peak flow,
reduce volume of water, improve water quality, use sustainable materials and natural vegetation,
improve aesthetics
Quantity Control - ANSWERoPostdevelopment runoff peak flowrate less than or equal to the
predevelopment peak flowrate
oFor multiple rainfall events, depending on jurisdiction (i.e., 25-year, 24-hour duration rainfall event)
oSome regulations also look at the volume of flow
, Quality Control
Type 1: - ANSWERwater-quality rainfall depth, determined from an analysis of local rainfall conditions
and data (i.e., 90th percentile depth). This yields a water quality volume (WQV), the runoff
corresponding to that event
Quality Control Type 2: - ANSWERspecify a fixed water quality volume regardless of catchment
characteristics.
o Idea is that most pollutants in runoff are contained in the first flush
o But! As imperviousness increases, runoff increases and thus the volume of water in the first flush
would increase
Quality Control Type 3: - ANSWERremove a minimum fraction of the annual-average load of specified
pollutants to be removed from runoff prior to discharge. Required removal is the removal efficiency.
Green techniques examples: - ANSWERHouses: use different strategies to collect, infiltrate and
cleanse rainwater ( splashblocks, rocks, furrows or channels, stormwater popups, planted
depressions, yard drains)
Streets: slope to one side and cut in curb direct rainwater into planted and grass sections
Swales: collect, absorb, and filter rainwater from streets and houses into the ground before going
into the city storm drain
Conveyance furrows: direct water away from the house via a path of gravel and crushed rock
Bioswales - ANSWERused as a means of both conveying water and also removing pollutants
Impoundments - ANSWERdepressed storage areas that collect surface runoff and release it at a
reduced rate
Detention basins - ANSWERstorage areas where stored water is released gradually, often used in
cases with minimal infiltration (dry most of the time)
detention basins advantages: - ANSWERmay be cheaper to implement due to having a smaller size,
may be required by regulations
