HigH Performance LandscaPe guideLines
Part ii: site assessment
site inventory & anaLysis
Is the site affected by tidal conditions, or are the sewers
impacted by tidal conditions? Where is the water table?
J In older urban sites that were built along the waterfront,
streams and wetland ﬂows were often placed in pipes; in
tidal areas, these pipes may include tide gates to prevent
water from moving under the site. However, when this is
either not the case or the tide gates have malfunctioned,
water levels will vary. Understanding these conditions will
inform the type and placement of BPs selected for the site.
Zoning anD coDe
How do the zoning and regulatory constraints relate to water?
J The site might be subject to ﬂoodplain high-water levels,
a regulatory ﬂoodplain, or coastal zone setbacks. Additional
issues related to mapped wetlands, steep slopes, protected
habitat, or other regulations should be documented.
What code issues apply?
J Local codes may require that the downspouts or storm
sewers connect directly to a public sewer. However, it may
be possible to design stormwater systems that manage water
on-site and only overﬂow to the public system.
siTe inVenTorY: conDiTions
An existing or new site survey is often the base map for park
site design. This survey should include topography, hundred-
year ﬂood lines, wetlands, tidal setback lines, built features,
trees, and existing utilities.
suggesTeD conDiTions for maPPing
The following information, when applicable, should be added to
the base plan by the designer. Depending on the size, location,
and typology of the park, not all information will be relevant.
HYDrologic feaTures anD flow PaTHs
J existing streams and wetlands
j Include any setbacks or buffers if applicable,
preliminarily deﬁned through NYSDEC and NWI wetland
J existing springs, seeps, and areas of ﬂow drainage,
such as swales
J mapped regulatory ﬂoodplains and areas of
j Floodplains are mapped on Flood Emergency
Management Agency Flood Insurance Rate Maps.
J buried streams and seeps, or past historical water features
j Consult historic maps from USGS, the Army Corps of
Engineers, and historic city infrastructure maps.
J areas of well-draining soils or wet soils.
J any relevant information gathered from soils tests
J sub-surface soil, water, and geologic information
j If structural borings or other tests have been conducted,
map available information on the depth to water table,
depth to rock, ﬁll conditions, etc.
J all existing utilities
J supplemental information
j Any supplemental information gathered from review
of historical or other documents should be included
J areas of concern
j Facility staff may indicate problem areas, such as wet
basements, seeps, standing water, and localized ﬂooding.
Water analysis focuses on three main areas: absorptive
capacity, surface permeability, and drainage. Speciﬁc items
for consideration are listed below.
What is the absorptive capability of the landscape?
J Conduct bulk density testing to determine soil
J Conduct percolation tests.
J Conduct soil analysis to determine natural inﬁltration
rates. Soil analysis can also determine if and what soil
modiﬁcations are necessary to create an engineered soil mix
that can absorb and ﬁlter water and also support the plants
integral to system function.
J Assess surrounding infrastructure — including buildings,
tunnels, and utilities — to ensure that inﬁltration areas do
not compromise these structures.
What impervious surfaces exist, and where it is feasible to
reduce or replace them with pervious surfaces?
J Examine street and sidewalk width requirements and
reduce where possible, keeping site usage in mind.
J Assess parking requirements, and determine if peak
loads can be accommodated with overﬂow parking using
J Consider replacement of asphalt or concrete pavements
with porous pavements.
J Examine paving demands to determine minimum paving
to meet need. In some cases, requested space may be larger
than actually necessary, and paving can be reduced. In other
areas, requested impervious land use may be inappropriate
for a speciﬁc area. Propose a reduction or a new location for
land use that better ﬁts in with existing site hydrology.