Step
3. Climate/Regional Factors
Both the design characteristics
and the best practice for a site can be influenced by regional factors such
as the topography, geography, or climate of a region. The following matrix identifies
five regional factors, including:
Arid/ Semi-Arid.
In these dry climates, the water conservation concerns may eliminate some
practices from consideration. Furthermore, practices need to be designed to
reflect the challenges in these regions.
Low Relief. In
areas of low relief, particularly those that are in coastal regions, STPs
that require minimal head and distance to groundwater are preferred.
Cold Climates.
In cold climates, practice selection or design needs to incorporate features
to deal with challenges such as winter snowmelt and frost heave.
Karst Topography.
Areas of karst topography presents specific challenges to STP designers, including
potential groundwater contamination and sinkhole formation.
High Rainfall.
Regions that receive high annual rainfall, and particularly those areas that
experience frequent hurricanes, make application of some practices challenging.
This
matrix will likely not appear in its entirety in many Stormwater Design Manuals.
If a manual is designed for a state, they may have some distinct climate zones,
or areas of karst topography. Furthermore, a STP manual writer may choose
to make finer distinctions, based on specific climate zones within a state.
|
| Matrix
3. Climate/ Regional Factors |
| Stp
Group |
Arid/
Semi-arid |
Low
Relief
(E.g., Coastal)
|
Cold
Climates |
Karst
Topography |
High
Rainfall |
| Ponds |
Conduct a water balance
analysis. Supplemental water may be necessary. |
Pond drain may not
be feasible. |
Incorporate design
features to improve winter performance. |
Encourage
use of a clay liner to prevent sinkhole formation, infiltration of hotspot
runoff.
Conduct geotechnical
tests to ensure that sinkholes do not form.
Allow a maximum ponding
depth of no greater than 4 feet to reduce the risk of sinkhole formation.
|
OK |
| Wetlands |
Restricted use due
to water supply. |
OK
|
Encourage the use of
salt-tolerant vegetation. |
| Infiltration |
OK |
Check distance to GW
table |
Incorporate features
to minimize the risk of frost heave.
Discourage infiltration
of chlorides.
|
For Karst where sinkholes
may form, discourage use.
For other Karst, encourage
heavy pretreatment.
|
May require more frequent
maintenance due to increased organic build-up in moist soils. |
| Filters |
OK |
Perimeter Sand Filter
is best option |
Incorporate design
features to improve |
OK |
OK |
| Open
Channels |
Select drought-tolerant
vegetation. |
Ensure minimum slope
can be achieved. |
Encourage the use of
salt-tolerant vegetation. |
Carefully analyze infiltration
when sink holes are a |
Ensure a thick vegetative
cover to reduce the risk of channel |
While
most climatic issues can be resolved with guidance, regulatory requirements should
be in place to prevent groundwater contamination and sinkhole formation in karst
regions.