Stormwater Management

Question 1

In order to support a shallow permanent pool, Shallow marsh systems need how large of a contributing watershed?

Answer 1

More than 25 acres

Question 2

Wet ponds should be generally designed to what depth?

Answer 2

4-8 Feet Deep

Question 3

Pocket wetlands are are typically adapted to serve what size of small sites?

Answer 3

One to Ten acres.

Question 4

The selection of a particular wetland design usually depends on what three factors?

Answer 4

Available Space,
Contributing Watershed Area, and
Desired Environmental Function

Question 5

Due to their small size and fluctuating water levels, these wetlands often have low plant diversity and poor wildlife habitat value.

Answer 5

Pocket Wetlands

Question 6

In many ponds, sediment storage of _______ cubic feet per acre of drainage area can store the sediment delivered over ______ years, after which maintenance for sediment removal would be necessary.

Answer 6

250, 5-10 years.

Question 7

Water-level rise of less than ______ during frequent water-quality events limits stress on wetland plants.

Answer 7

1 Foot Deep

Question 8

Total flood storage depth is measured from the ______ invert.

Answer 8

Outlet

Question 9

Techniques for implementing stream restoration, stabilisation, and enhancement can be thought of in which three categories?

Answer 9

Structural,
Biological, and
a Combination referred to as Soil Bioengineering.

Question 10

When feasible, urban streams should be buffered with a minimum of _______ undisturbed forest, and an additional ________ of managed vegetated area

Answer 10

8 metres (25 ft), 15-30 metres (50-100 ft)

Question 11

The process of removing soluble nutrients, metals, and organics by binding ions and molecules to other particles of organic matter or clay. This most commonly occurs in the soil as run-off infiltrates

Answer 11

Absorption

Question 12

Soluble nutrients can also be removed from storm water by plants in a process called _______. Both toxic heavy metals and essential mineral nutrients are taken up by the roots of the plants and deposited in stems, shoots, or leaves of the plants.

Answer 12

Phytoremediation

Question 13

Is a chemical activity where a contaminant is changed to a more volatile vapor form. In stormwater management systems, this function transforms complex hydrocarbons, gasoline or other petroleum products in the runoff, into carbon dioxide.

Answer 13

Volatisation

Question 14

How should sediment be removed?

Answer 14

Through the use of filter strips or sediment traps before it enters an infiltration device.

Question 15

All surface runoff from paved and unpaved areas is collected and conveyed on the ground, primarily by swales.

The system is discharged or directed to an on or off-site drainageway, stream, or other natural watercourse, an existing street or municipal storm
drainage system, or an on-site retention or sediment pond

Answer 15

Open Drainage System

Question 16

Surface runoff from paved and unpaved areas is collected at surface inlets and conveyed by underground pipes to an outlet either on or off the site.

Disadvantages include increased cost and complexity
of the system, potential for erosion at the discharge point due to the greater concentration of runoff, reduced filtering of sediment because of increased velocity of the storm water in the pipes, and reduced opportunity for storm water to infiltrate the soil.

Answer 16

Closed Drainage System

Question 17

Typically, the open system is used in unpaved areas with the intent of providing more opportunity for the storm water to infiltrate the pervious surface, whereas the closed system is used in paved areas. The advantages of this system are reduced construction costs, as compared with a totally closed system, lower potential for soil erosion because of reduced volumes of surface runoff, and lower potential for erosion problems at the outfall because of lower volumes in the pipes.

Answer 17

Combination Drainage System

Question 18

The required dimensions for grassed swales may be determined analytically or by a variety of published ______ or other design aids. To determine the required dimensions of a swale, the ______ to be handled must be known.

Answer 18

Nomographs, Rate Runoff

Question 19

Storm water runoff from upslope areas should be prevented from crossing ______ or ______ soils. Diversion measures can be effectively utilised to redirect runoff. Where diversion is not possible, ______ should be used to reduce runoff velocities.

Answer 19

Disturbed or Exposed.
Vegetative Buffer Strips.

Question 20

An appropriate technique for the repair of small earth slumps that are frequently wet.

Answer 20

Live Staking

Question 21

Involves the insertion of tamping live, rootable cuttings into the ground. Creates a stabilizing mat that reinforces the soil.

Answer 21

Live Staking

Question 22

Long bundles of branch cuttings bound together into sausage like structures (Figure 11.4) with the branches and bud ends oriented in the same direction. These bundles are capable of propagation.

Answer 22

Live Fascines

Question 23

Is somewhat similar to the live fascine system, except that the ______ are oriented primarily perpendicular to the slope. This orientation is more effective in terms of earth reinforcement and mass stability.

Answer 23

Brushlayering

Question 24

Effective technique for stabilizing slopes by reducing erosion and face sliding.

Placed in shallow trenches parallel to contours for dry slopes, and at an angle to the contours for wet slopes, and are anchored with live and dead stakes.

Answer 24

Live Fascines

Question 25

_____ cuttings, usually in criss cross fashion, on small benches excavated into the slope and then covering them with soil.

Answer 25

Brushlayering

Question 26

______ installations are constructed and function similar to brushlayering, except with addition of vertical live staking to improve initial structural stability. This installation is used specifically for repairing small, localised slumps or holes.

Answer 26

Branch Packing

Question 27

______ are box-like structures fabricated with untreated timbers and filled with layers of live branch cuttings and soil or other appropriate backfill material. This type of structure is employed in place of low walls at the bottom of cut-or-fill slopes to stabilise the toe of the slope and reduce its overall steepness, providing immediate protection from erosion and sliding. The branch cutting should be installed to extend into the slope.

Answer 27

Live Cribwalls

Question 28

A reasonable rule-of -thumb for the proper amount of silt fence is—at least ______ of silt fence per ______ square feet of disturbed area

Answer 28

100 Feet, 10000 Square Feet

Question 29

Grass swales tend not to erode if velocities do not exceed _____ per second.

Answer 29

1200mm (4ft)

Question 30

Vegetated or matted embankments typically require a ______ to accommodate machine or hand maintenance.

Answer 30

1:2 maximum slope

Question 31

______ and ______ are the primary movers of storm water runoff in watersheds from the rainfall source to the sea.

Answer 31

Streams and Rivers

Question 32

Slope failure occurs when….

Answer 32

Shear stress exceeds sheer strength