Environmentally Sensitive Areas

Environmental Services provides guidance and support to the Community to understand and appreciate Environmentally Sensitive Areas and provides guidance to the Development Community on how to sensibly develop on property with Environmentally Sensitive Areas.

Local Environmentally Sensitive Areas

• The Many Benefits of a Healthy Waterway

  Promote Community Wellness. The City of Denton relies on surface water from Denton: runoff draining off our land and through streams, and entering Lakes Ray Roberts and Lewisville, the City's drinking water source. Our residents' health benefit from using nature to maintain high water quality. Vegetated buffers also serve as a source of greenspace. Even small outdoor spaces can serve to reduce health risks, encourage general wellness and accomplish specific social or psychological benefits.

  Provide Monetary Benefits. Vegetative buffers protect private property that can be substantially threatened when changes in waterway alignment occur. Although natural streams and waterways are dynamic and can be expected to meander, vegetative buffers reduce the potential for expedited property loss.

  Increase Bank Stability. Herbaceous and woody plants in riparian buffers strengthen the stream bank as the root system penetrates through the topsoil and into the bedrock, adding flexible strength that can resist stresses, such as flood events.

  Reduce the Negative Effects of Urbanization. Historically, urbanized areas have experienced a disruption in the natural water balance, including increased peak flood events, increased stormwater runoff, more frequent flooding, increase bank-full flows, lower dry weather flows and reduced groundwater discharge. Vegetated buffers offer a measure of protection from these effects by readily absorbing runoff and holding moisture.

  Remove Pollutants. Vegetated buffers are an effective and economical way to filter and sequester sediment, metals, nutrients, and other chemicals, reducing water pollution.

  Serve as a Source of Ecological Resources. Vegetation, microorganisms, macroorganisms, and other inhabitants in and around streams uptake and convert harmful chemicals and excess nutrients into complex organic forms of nutrients, recycling important resources for ecological food cycles.

  Provides Wildlife Habitat and Corridors. Stream life includes bacteria, algae, aquatic insects, fish, amphibians, reptiles, and mammals. All require a hospitable aquatic environment to live, produce, interact, and thrive. Riparian buffers adjacent to water plays a crucial role in maintaining a range of suitable habitats and conditions within the channel for a diverse and self-sustaining cycle of aquatic life. In the urban setting, riparian buffers provide connectivity between patches of habitat, allowing wildlife to use these corridors for dispersal and migration.
  
  

• Official Environmentally Sensitive Areas Map
  The City of Denton has adopted an Official ESA Map of Environmentally Sensitive Areas throughout the City, identified through the best information available from aerial photographs and records such as a soil survey from the Natural Resource Conservation Service (NRCS) and FEMA floodplain maps. It is important to know that the boundaries of some unstudied ESAs may be updated based on the most current information available.
  You may view the Official ESA Map on the City of Denton Online Map Viewer by turning on the ESA layer.

The Four Distinct Environmentally Sensitive Areas

• Floodplain
  
  
  Floodplain ESA exists on the terraced banks surrounding waterways where the land is subject to flooding. Floodplain ESA habitat is often an extension of the more sensitive Riparian Buffer habitat that exists immediately surrounding waterways.
  
  Typical Floodplain ESA habitat is dominated by tree species that can tolerate intermittent flood events, such as cedar elm, pecan, western soapberry, American elm, Osage orange (bois d’arc), hackberry (sugarberry), and honey locust. Floodplains on the prairie soils on the western side of Denton may be dominated by switchgrass and other native grasses and vegetation. Floodplains are an important part of riparian ecosystems that traps sediment and particulate organic matter outside the active channel during overbank flows and flood events. Protected floodplains allow waterway channels to accept deposition and erosion, leading to natural meandering and providing a defense against damaging flood events.
   
• Riparian Buffers
  
  
  Riparian Buffers are the land and vegetated areas adjacent to lakes, streams, rivers and wetlands. Riparian Buffers have complex ecosystems and provide food, lodging, and travel corridors for both aquatic and terrestrial species and serve as the most important link between upland forests and aquatic habitats. Often, these vegetated areas are the last line of defense to protect the water quality of a waterway. A properly functioning riparian area is when adequate vegetation, landform or woody material is present to dissipate stream energy associated with high waterflow, thereby reducing erosion and improving water quality; capture sediment and aid floodplain development, improve floodwater retention and ground-water recharge, develop root masses that stabilize streambanks against erosion; and maintain channel characteristics.
• Water-Related Habitat
  Denton regulations require the preservation of areas designated as wetlands, bottomland hardwood forests, and deep water habitats. These habitats are typically found on the first terrace of a floodplain and overbank flow areas surrounding ephemeral and intermittent streams and in low-lying areas that are inundated for short periods of time to permanently wet soils. Many water-related habitats are considered jurisdictional Waters of the U.S. and will have over-lapping federal protection requirements. Areas that may be considered non-jurisdictional wetlands should also be assessed as water-related habitat. If confirmed to be water-related habitat, then the areas will be subject to the City of Denton protection requirements.
  
  Wetlands are characterized by having a high water table level as a driver for the biological and chemical processes typical of wetlands. Wetlands are defined as areas with soils that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that do support under normal circumstances, a prevalence of vegetation typically adapted for life in saturated conditions.
  
  
  
  Bottomland hardwood forests are deciduous forested wetlands and river bottoms with alluvial soil deposition. Periodic to constant wet conditions support certain species of trees such as pecan (Carya illinoinsis), Texas hickory (Carya texana), American elm (Ulmus americana), chinkapin oak (Quercus muehlenbergii), chittamwood (Sideroxylon lanuginosum), green ash (Fraxinus pennsylvanica), black walnut (Juglans nigra), indigo bush (Amorpha fruticose), Texas persimmon (Diospyros texana), Shumard oak (Quercus shumardii), sycamore (Plantus occidentalis) and Carolina buckthorn (Frangula caroliniana); and prevents the establishment of upland tree species that are not flood tolerant. These habitats are typically found on the first terrace of a floodplain and low-lying areas that hold water for a short period of time. Denton defines this habitat as areas that contain at least 50 percent of native trees and understory vegetation that make up a bottomland hardwood forest.
  
  
  
  
  
  
  
  
   
• Cross Timbers Upland Habitat
  The Cross Timbers region is a mosaic of deciduous forest and prairie that connects the eastern forests and southern Great Plains. The Eastern Cross Timbers is geologically restricted to soils that are sandy or sandy loam derived from sandstone parent material, which drains well. The region’s unique geology and climate has resulted in a mixture of prairies that include grasses and wildflowers and forests with an understory of shrubs, vines and herbaceous plants. The woodlands are dominated by post oak (Quercus merican) and blackjack oak (Quercus marilandica), but also contains populations of other woody species such as cedar elm (Ulmus crassifolia), hickory (Carya spp.), American  beautyberry (Callicarpa Americana), coralberry (Symphoricarpos orbiculatus), eastern redcedar (Juniperus virginiana), mesquite (Prosopis glandulosa), and greenbriar (Smilax spp.) Common to the Cross Timbers habitat are native grass species in interspersed pocket prairies.
  
  
   

Guidance for the Development Community

• Environmentally Sensitive Areas Assessment Forms
  When a property owner is proposing land clearing, land disturbances or would like to contest the designation of an area on the property the property owner should apply for and follow the procedures for an ESA field assessment. Field assessment forms may be completed by City of Denton Staff or by a qualified biologist or wetland specialist.
  
  Floodplain Assessment Form
  Riparian Buffer Assessment Form
  Water-Related Habitat Assessment Form
  Upland Habitat Assessment Form