What Everybody Ought to Know About Identifying Existing Site Conditions

Site Inventory Series Logo for the California Supplemental Exam (CSE) for landscape architects.Identifying existing site conditions is one of the many job tasks in the inventory section of the California Supplemental Exam for landscape architects. Understanding the purpose of site inventories is one area where candidates can expect a question or two on the CSE.

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This article focuses on why landscape architects inventory a site early in the design process. According to the CSE Candidate Guide, landscape architect candidates are required to be knowledgeable about the purposes for identifying existing site conditions.

Associated Knowledge Area: “Knowledge of purposes for identifying existing site conditions (e.g., natural, cultural, site features, infrastructure).”

There is likely one or more questions on the CSE about the reasons why landscape architects perform site inventories at the beginning of the design process. There are three steps that lead to an initial design solution on a site. The first step is site inventory. Next, the site analysis step of the design process uses information gathered during the site inventory phase along with program information from the client to inform the preliminary design phase (but we will discuss this in another article).

The entire process begins with an inventory of the site.

What is Site Inventory?

According to the Dictionary of Landscape Architecture and Construction by Alan Jay Christensen, site inventory is defined as, “[g]athering and categorizing data and information on natural and human features in an area proposed for a planning project”.

Landscape architects perform site inventories early in the design process to gather useful, high quality information that is used during the site analysis phase of a project.

Site inventories will necessarily vary in their degree of complexity and the types of information required depending on the type of site, location, scale, and scope of the project.

Site inventory is the first step in the design process. Before any site analysis can be performed by a landscape architect, a thorough site analysis needs to be completed. Site inventory is a form of contextual inventory. Proper site inventory techniques and concepts lead to a thorough understanding of the project site and context and which frequently leads to optimum site solutions and the best utilization of the site to meet the client’s needs during the design process.

Site inventory and analysis are performed as the first steps of the design process. Understanding the existing conditions of the site and its surrounding context helps inform the designer and leads to identification of problems and potential uses of a site that maximize the client’s value.

Existing site conditions can be organized into four categories:

  1. Natural Existing Site Conditions
  2. Cultural Existing Site Conditions
  3. Existing Site Features
  4. Existing Infrastructure

We will explore each topic in future articles. This article explores the purpose of site inventories and discusses some common reasons why landscape architects conduct site inventories.

Why Are Site Inventories Important?

The site is a living organism and is in a constant state of change. Landphair & Motloch

Before we get in to specifics, lets first review some general reasons why landscape architects include site inventory as a step in the design process.

  • Site inventories are important because the information gathered during the inventory process fuels site analysis and the rest of the design process.
  • A thorough site inventory assists landscape architects make sound site engineering and site design judgements.
  • Site inventories provide data to later integrate natural and man-made systems later on in the design process.
  • Information discovered during site inventories can lead to design solutions which capitalizes on the sites strengths while minimizing negative affects from site weaknesses constraints.

Why Identify Existing Natural Conditions?

You can probably think of many reasons to identify existing natural site conditions.

Site development causes the existing site and its natural systems to change. Knowing what systems exist and how they function prior to development can help inform designers how to integrate new site functions into existing natural systems and avoid creating new conflicts in the future.

As landscape architects, it is our duty to protect the public’s health, safety, and welfare as licensed professionals. By identifying problematic natural conditions early in the design phase, landscape architects can integrate their findings into site designs and avoid creating safety hazards.

Here are some natural conditions that landscape architects need to include in site inventories:

Geologic Substrate

Knowledge of the geologic substrate can help designers determine if they underlying geology will pose significant limitations on site development. Some examples of problems that a site inventory can uncover include:

  • Impervious geology
  • Soluble geology
  • Geology prone to land slides
  • Shallow bedrock which will increase grading and foundation costs.


Soil is all around us but taken for granted until we find its limitations that hinder a project’s potential. Here are some reasons for exploring soil-related factors during the site inventory process:

  • Identify expansive soils (which will raise construction costs)
  • Locate poor-draining soils
  • Identify fertile or infertile soils
  • Note areas or soils prone to erosion
  • Determine if soils have an adequate bearing capacity for proposed development.

Topography and Landform

Topography is the single most influential natural site condition that greatly determines where and how development of a site will commence. Landform determines which parts of the site are suitable for construction of structures and circulation systems. Topography and landform affect other natural systems because they direct water and energy flows on the site.  Here are some reasons why site inventory is useful:

  • Identify areas that are too steep for development
  • Locate parts of the site suitable for development
  • Find shallow grades that will not drain properly or require excessive (and expensive) drainage remediation.


Hydrology deals with water storage and movement through a site and includes surface and subsurface occurrences. Water has the ability to erode and deposit sediment and affect the way soils develop. Landscape architects need to understand the complex interrelationships between surface and subsurface water and how it affects a site.

What too look for with subsurface hydrology:

  • Identify if the water table is extremely close to the surface.
  • Determine if expansive materials are in the groundwater fluctuation zone
  • Be able to find out if groundwater water quality is inadequate for human or landscape use.
  • Determine permeability and groundwater recharge capacity ability.
  • Research the site’s suitability for septic systems.
  • Determine the liquefaction risk of a site.

Here are some site inventory factors to observe for surface hydrology:

  • Identify areas prone to erosion and sedimentation.
  • Locate natural water courses and streams or rivers on a site.
  • Determine which watershed the site belongs to.
  • Find out if the site is located in a flood zone.


Most of the planet’s land surface is covered in some sort of vegetation. As landscape architects, we take a keen interested in identifying the type and species existing on a site prior to development. Vegetation is intimately linked to soil and hydrology. As landscape architects investigate the site, they are interested in identifying the following:

  •  What is the basic plant community found on the site (i.e. coastal sage scrub, chaparral, etc.)
  • Which species are present on the site prior to development.
  • Which plant associations are found on the site.
  • Do changes in plant associations indicate different soil or hydrologic conditions.
  • Does existing vegetation pose a hazard to development? Is it highly flammable, toxic, contain invasive exotic species, etc.


We all are familiar with the overall climate of California, but each site has its own microclimate variations which are unique to its location. Site inventories can uncover important local variations in the microclimate that may prove useful later in the design process.

  • Identify areas that may be uncomfortable for humans due to reflected heat, extreme wind velocity, high humidity, or other environmental factor.
  • Note areas where cold air collects and creates frost pockets that will damage tender vegetation.
  • Locate the dominant direction of the wind. Note if wind directions change at different times of the year.
  • Will reflected heat or wind speed affect what plants and program activities occur on the site?

There are many good reasons why landscape architects include natural existing conditions. The purpose of uncovering this hidden site information can dramatically improve site analysis and design solutions while protecting the health, safety, and welfare of site users.

Why Identify Existing Site Features?

Site features are existing natural and man-made conditions that are of particular importance or significance. During a site inventory, landscape architects seek out information on particularly unique, desirable, or sensitive natural features. There are many reasons for identifying existing site features, including one or more of the following:

  •  Are there any existing structures on the site?
  • What views on and off-site exist?
  • Are there existing pedestrian or vehicular systems on the site?

Why Identify Existing Infrastructure?

During site inventories, landscape architects should identify what types of existing utilities and infrastructure exist on or adjacent to the site. Knowing what types of utilities are on the site can be really useful during the rest of the design process. Some additional reasons for identifying existing infrastructure and utilities include:

  • Does the site have electrical service? If not, is there electrical service adjacent to the site?
  • Does the site have access to municipal water and sewer service? If not, can water or sewer lines be extended to the site?
  • Is there an existing storm water system that services the site or adjacent areas?

Why Identify Cultural Conditions?

Candidates must demonstrate an ability to identify existing cultural conditions during the site inventory process.

Human and cultural context (activities, human relationships, patterns of human characteristics) include:

  • What is the median population age and age distribution?
  • Describe the average density.
  • What values are held by adjacent residents or the site’s community?
  • What sort of informal activities take place in and around the site?
  • Are there festivals held on or near the site at certain times of the year?
  • Are there occasional parades, street fairs, or craft fairs held nearby?
  • What are the local vandalism & crime patterns?
  • Are there recreation facilities and parks in the area?

Understanding the cultural landscape that the project exists in also involves understanding the basic demographic information about the surrounding area and comprehending the attitudes of the population.

There are many reasons why landscape architects conduct site inventories as the first step in the design process. Understand the reasons why we inventory a site and why we look for factors that may negatively impact the public’s health, safety, and welfare.

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John is a landscape architect who is currently preparing to take the California Supplemental Exam to become licensed in California. He is currently a licensed professional landscape architect in Georgia and Florida. John graduated from California State University, Pomona with a BSLA degree in landscape architecture in 1997 and has extensive practice experience in residential and commercial landscape design.

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