2021-100 ESA InventoryDate: November 19, 2021 Report No. 2021-100
INFORMAL STAFF REPORT
TO MAYOR AND CITY COUNCIL
SUBJECT:
Summary of a report and discussion of the Environmentally Sensitive Areas inventory at the
Committee on the Environment held on November 12, 2021.
BACKGROUND:
The purpose of this report is to provide City Council with a summary of the a discussion held by
the Committee on the Environment (COE) on November 12 about an inventory of environmentally
sensitive areas (ESAs) map initially requested by Council on August 10, 2021.
DISCUSSION:
Staff presented updated acreages for the four protected habitats (Undeveloped Floodplain, Water-
related Habitats, Riparian Buffers, and Cross Timbers Upland Habitats), general conclusions
derived from the changes in ESA acreages since 2002, and discussed the new available information
obtained from ESA field assessments. Additionally, proposed ESA-related Development Code
amendments and proposed future considerations on how to further analyze the ESA inventory were
shared.
The Committee expressed interest in:
Looking at ecological biofunctions for ESA definitions,
Looking at acreage considerations for Cross Timbers Upland Habitat preservation,
Researching how ecologically important areas are preserved during development in
neighboring cities, including the Town of Flower Mound,
Researching grassland and prairies habitats in Denton and looking at option to define
prairies as an ESA, and
Providing ESA inventory changes as part of Council public hearings.
CONCLUSION:
Environmental Services staff has comprehensively analyzed all the changes that have been made
to the map since it was adopted in 2002, categorized the changes and provided updated acreages,
and made the information readily available to ESA map viewers.
EXHIBITS:
1. Staff Report
2. Staff Presentation
STAFF CONTACT:
Deborah Viera
Assistant Director of Environmental Services
(940) 349-7162
Deborah.Viera@cityofdenton.com
Environmental Services Report
An Analysis of the comprehensive Environmental Sensitive Areas (ESA) inventory
SUBJECT:
Receive a report and hold a discussion regarding the comprehensive Environmentally Sensitive Areas (ESA)
inventory.
BACKGROUND:
Environmental Services staff has finalized work on the Environmentally Sensitive Areas (ESA) map initially
requested by Council on August 10, 2021. The intent of the improvements were to add information obtained from
ESA field assessments and make it readily available to ESA map viewers. While most of the information was
always been available upon request; since October 6, 2021 the information has been available online. No graphical
changes were made to the map. The mapped features are based on the original 2002 map or have been updated to
reflect changes made following the ESA Field Assessment procedure. Each type of ESA is shown on the online
map as a separate layer that may be turned on/off by the viewer.
Staff has comprehensively analyzed all the changes that have been made to the map in the almost 20 years since it
was adopted. The analysis includes categorizing changes that have been made to the map and summarizing the number
of acres within each category.
A change to the definition of the Floodplain ESA has been proposed and is currently under review with the
Development Code Review Committee. There has been discussion of changes to the Cross Timbers Upland Habitat,
but no proposal has been made.
MAP ATTRIBUTE ADDITIONS:
Since the official ESA map was adopted in 2002 staff retained the fidelity of the map by strictly documenting changes
to the geometry of the field-assessed ESAs. ESA field assessment case numbers and field-assessed ESA designations
have been available map features since 2007.
A recent map attribute update project was undertaken to add more information about each feature. The geometry of
the features was not modified through this project. The following table provides a summary of the attributes that were
added:
ATTRIBUTE CHANGE INFORMATION DESCRIPTION
ESA Status Updated "Not Assessed"
“Designation Confirmed"
"Designation Removed"
Updated terms used.
Project Status New "Current"
"Expired"
"Final"
ESA Field Assessments expire after 2 years.
The designation is considered final when a
final plat has been approved or staff does not
have reason to believe the habitat designation
will change in the future (e.g., riparian zone
is a concrete flume).
Description New Summary of ESA Field Assessment findings
and activity that affected the habitat
Change Class New "Added"
"Less than 10 ac"
"Removed by Right"
"AESA"
"Exempt"
"Lacks Characteristics"
"Pre-2002"
"Reclass"
Added: indicates when a feature was added
to the original ESA map,
Less than 10 ac: indicates Cross Timbers
Upland removed when contiguous forest was
less than 10 acres,
Removed by Right: used in the Upland
Habitat to indicate when the DDC permitted
a portion of forest to be removed,
AESA: indicates when a feature was
modified by an approved Alternative ESA
Plan,
Exempt: some development is exempt from
protection requirements (e.g., thoroughfares),
Lacks Characteristics: defining
characteristics of the ESA type not found
during field assessment,
Pre-2002: development rights preceded the
2002 adoption of the Official ESA Map,
Reclass: applied when field assessment
determined need to change ESA type.
Approved Date New Date the field assessment approved by
Environmental Services staff
Expiration Date New Two years after field assessment approved
by the Development Services Director, as
indicated by the memo date
Previous
Project
New When appropriate, lists any previous
development-related projects associated with
the habitat
ANALYSIS OF ESAs:
Following the addition of the attributes described above, staff identified and placed each feature into one of these
seven categories:
CATEGORY DESCRIPTION
Potential ESA ESAs as originally mapped in 2002. ESAs are assessed for confirmation of the
original designation through a field assessment of current conditions. This
procedure is typically completed prior to the approval of development or other
land disturbing activities.
Potential ESA in ETJ Regulatory authority will apply to Riparian Buffer ESAs, Water-Related
Habitats and Cross Timbers Upland Habitats in the ETJ after annexation. The
city has regulatory authority of Undeveloped Floodplain ESAs in the ETJ.
ESA Confirmed to Exist The feature has been assessed and found to have the characteristics of the
identified ESA.
ESA Permanently
Protected
These areas have been confirmed to be an ESA and placed into permanent
protection, such as an HOA lot, a drainage easement, a conservation easement,
park dedication, or similar instrument.
Area is Not an ESA Some features shown on the original map are found through ESA field
assessments to lack the characteristics that define them as ESAs.
ESA Removed Prior to
2002
Some legacy development projects retained development rights obtained prior to
the adoption of the protection requirements in 2002. These rights were not
reflected in the original map.
ESA Removed by Right Developments proposed after 2002 are subject to the DDC standards, including
permission to remove a portion of the habitat. This category also includes
activities that are exempt from protection requirements, such as major roadways.
Below is a summary of the number of acres of each type of ESA by category:
CATEGORY FLOODPLAIN
ESA
RIPARIAN
BUFFER ESA
WATER-
RELATED
HABITAT
CROSS
TIMBERS
UPLAND
HABITAT
Potential ESA 8,390 4,166 2,436 1,737
Potential ESA in ETJ 15,973 4,163 3,658 2,800
ESA Confirmed to Exist 332.8 114.8 80.0 48.6
ESA Permanently
Protected
63.0 61.1 63.6 107.5
Area is Not an ESA 432.4 685.1 43.0 256.6
ESA Removed Prior to
2002
323.9 13.0 693.3
ESA Removed by Right 5.7 12.5 11.4 178.5
The following are a set of maps showing the categories applied to each of the ESA types:
Floodplain ESA
Riparian Buffer ESA
Water-Related Habitat
Cross Timbers Upland Habitat
DISCUSSION:
ESA Field Assessments on private property require a request from the property owner(s) and are typically requested
prior to proposed land disturbances. Thus, a vast number of acres of ESAs identified on the official ESA map have
not been confirmed to exist because the ESA is located on private property and is not accessible to determine its status.
Of those features that have been assessed, staff has determined the greatest changes to the official ESA map has been
the result of identifying features on the official ESA map that, once assessed in the field, did not meet the criteria of
an ESA. Many of the Riparian Buffer ESAs that had originally been identified, for example, were located within the
core of the city where the waterway had been heavily modified before the map was adopted.
The other major change to the map was the result of land disturbances on property with vested rights. This includes
the Robson Ranch development (PD 173), Country Lakes (PD 174) and The Preserve (PD 132). These Planned
Developments had sought approval for the development prior to the adoption of the official ESA map.
Floodplain ESAs, Riparian Buffer ESAs, and Water-Related Habitats that were removed by right include ESAs within
roadway rights-of-way and features removed by an approved Alternative ESA Plan.
Seventy-seven percent (152.2 of the 178.5 acres) of Cross Timbers Upland Habitat was removed by right as allowed
in the Denton Development Code (DDC). The remaining 23% was the result of roadways and other exemptions. Since
2002 residential development has been required to preserve a minimum of 50% of the Upland Habitat and has resulted
in the removal of 70.3 acres. From February 2002 until February 2018 the DDC permitted non-residential properties
to remove 100% of Upland Habitat and resulted in the removal of 9.7 acres. In 2018, the DDC was amended to require
non-residential development to preserve a minimum of 30% of the Cross Timbers Upland Habitat. One significant
project removed 46.4 acres of Cross Timbers Upland Habitat around Unicorn Lake upon approval of an Alternative
ESA Plan.
The amount of land within the City of Denton and the ETJ where ESAs potentially exist or have been confirmed to
exist totals 32,707 acres, which is nearly 20% of the total City of Denton and ETJ land mass (166,064 acres).
This report is a snapshot of the status of ESAs as of November 2021. The results of this analysis are not static as there
are many factors that will further change the map in years to come. Through the addition of the new map attributes
staff will more readily be able to track these changes over time.
Next proposed steps are to refine analyses of the map. By incorporating the ESA map with city canopy records, staff
is proposing to identify how each of the ESA types help meet the city-wide canopy goals. A special focus study of the
Cross Timbers Upland Habitat will inform decisions makers in protecting this ecological resource. Lastly, staff will
assess the need to strategically update the geometry of some features to reflect more current conditions.
PROPOSED DDC CODE AMENDMENTS:
Staff has identified and proposed two sets of code amendments. These amendments are currently under review with
the Development Review Committee.
1. Amend Section 9.2 Undeveloped Floodplain
Areas within the FEMA one-percent Annual Chance Floodplain (a.k.a. 100-year floodplain) or areas
identified by a City accepted and approved study of the one percent Annual Chance Floodplain, that are
undeveloped and in their natural state.
Reason: Developments providing a detailed one-percent Annual Chance flood study (City accepted and
approved), may delineate a floodplain that varies from the FEMA floodplain boundary, potentially
identifying property that could be recovered. Currently, development is restricted to areas outside the
effective floodplain boundary by the Undeveloped Floodplain and Floodplain Development ESAs
definitions. A LOMR would still be required to modify the effective floodplain boundary.
2. Add allowances for trails in ESAs
Section 7.4.7A: Riparian Buffers and Water-Related Habitats
Pathway clearings to establish and maintain publicly owned and publicly operated pathways and trails,
subject to approval by the Department of Environmental Services.
7.4.8A: Cross Timbers Upland Habitat
Re-establishment and maintenance of clearings, old roads and open space for publicly owned and publicly
operated pathways and trails, subject to the approval by the Department of Environmental Services.
Reason: Support the Parks Department Master Trails Plan.
20 Years of Protection:
An Analysis of the Official ESA Map Inventory
1 COE21-022 11/12/21
Original Environmentally
Sensitive Areas Map
Cross Timbers Upland Habitat:Contiguous areas ten acres or
larger of cross timbers habitat. 5,616 acres
Water-Related Habitat: Areas designated as wetlands, and
trees and understory vegetation containing 50 percent or more
of predominantly native bottomland hardwood. Bottomland
hardwoods occur on the first terrace of floodplains and flats
along channels. Periodic inundation prevents establishment of
upland species and maintains the functioning of this type of
vegetation. 12,184 acres
Riparian Buffer: Areas within 100 feet, measured from both sides
of the stream centerline, with drainage areas greater than one
square mile, and 50 feet from both sides of any streams
centerline that drain areas of one square mile or less. This also
applies to the outer edges of surface water bodies. 9,370 acres
Floodplain ESA: Areas within the FEMA one-percent Annual
Chance Floodplain (a.k.a. 100-year floodplain), that are
undeveloped and in their natural state. 27,380 acres
2 COE21-022 11/12/21
Status of Environmentally
Sensitive Areas Today
32,707 acres of land has a designation of either potential ESA
or confirmed ESA.
3 COE21-022 11/12/21
2021 Record Improvements to ESA Maps
Environmental Services recently re-published the ESA maps with the following record enhancements. Other information, such as the location, size and status of ESAs, was retained. The new
information results in improved communication and analysis.
Habitat Map
Water-Related
Habitat Map
Cross Timbers
Upland Habitat
Map
1 Created a map for each
habitat type 2 Added and Updated Attributes and Information
4 COE21-022 11/12/21
Analysis of the Comprehensive ESA Inventory
5 COE21-022 11/12/21
Cross Timbers Upland
Habitat
1,737.0
2,800.0
48.6 107.5
256.6
693.3
178.5
0
500
1000
1500
2000
2500
3000
6 COE21-022 11/12/21
Water-Related Habitat
2,436
3,658
80.0 63.6 43.0 13.1 11.4
7 COE21-022 11/12/21
Riparian Buffer ESA
4,166 4,163
114.8 61.1
685.1
323.9
12.5
8 COE21-022 11/12/21
Floodplain ESA
8,390
15,973
332.8 63.0 432.4
5.7
Lake Ray Roberts -15,939 acres
Lewisville Lake -3,292 acres
9 COE21-022 11/12/21
Proposed ESA Definition Revisions
AMEND Section 9.2 Undeveloped Floodplain
Areas within the FEMA one-percent Annual Chance Floodplain (a.k.a.100-year floodplain) or areas identified by a City accepted and approved study of the one percent
Annual Chance Floodplain, that are undeveloped and in their natural state.
Reason: Developments providing a detailed one-percent Annual Chance flood study (City accepted and approved), may delineate a floodplain that varies from the FEMA
floodplain boundary, potentially identifying property that could be recovered.Currently, development is restricted to areas outside the effective floodplain boundary by
the Undeveloped Floodplain and Floodplain Development ESAs definitions.A LOMR would still be required to modify the effective floodplain boundary.
ADD to Section 7.4.7A: Riparian Buffers and Water-Related Habitats
Pathway clearings to establish and maintain publicly owned and publicly operated pathways and trails, subject to approval by the Department of Environmental
Services.
ADD to 7.4.8A: Cross Timbers Upland Habitat
Re-establishment and maintenance of clearings, old roads and open space for publicly owned and publicly operated pathways and trails, subject to the approval by the
Department of Environmental Services.
Reason: Support the Parks Department Master Trails Plan.
10 COE21-022 11/12/21
Future Considerations
How preservation of each of the ESA types help meet the city-wide canopy goals?
How much of the remaining potential Upland Habitat areas are less than 10 acres in size?
o Statistical analysis of forest size categories
Future preservation: how much of the remaining Upland Habitat forest could be preserved with the current code, 50%
preservation for residential development and 30% preservation for commercial development?
o How much Upland Habitat is located within certain zoned properties and/or future land use designations?
o How much could be potentially be preserved by Park and Open Space Plan?
o How much Upland Habitat is currently on private property or on public property?
Assess the need to strategically update the geometry of some features to reflect current conditions:
o Riparian Buffers -waterways that have shifted over time
o Cross Timbers Upland Habitat and Water-Related Habitat -adjust geometry of some features to reflect improved aerials
11 COE21-022 11/12/21