EL PASO COUNTY POLICY PLAN


 CHAPTER 1-B  SECTION 11 DRAINAGE AND FLOOD PROTECTION
BACKGROUND
 
Due to a semi-arid climate and the topography of the Front Range, many of the drainage channels in El Paso County are naturally dynamic and unstable. As new development occurs, impervious surfaces replace a portion of natural permeable surfaces. Impervious surfaces contribute to increased and concentrated stormwater flows from rain and snow melt and can have an adverse impact on stormwater quality. A drainage system’s failure to adequately manage increased stormwater flows may also result in serious property damage, loss of life and impacts to area wildlife and the environment.
 
Responsibility for construction and maintenance of drainage facilities in unincorporated areas has traditionally been shared between individual property owners and the Public Works Department. Historically, there has not been a dedicated revenue source for funding public drainage systems. More recently, a regional fee system has been developed, using a basin planning approach. Out of a total of 139 identified basins approximately 30 have now been studied in detail, with fees developed; however, these calculated per-acre fees are only collected at the platting stage, and do not include funding for maintenance. Alternative funding methods, based on impervious surface coefficients from roofs and paved areas, and/or drainage utility fees, are being considered by a regional task force.
 
Flood plain management in El Paso County is subject to federal mandates and is largely a function of the Regional Building Department. Approximately four percent (4%) of the entire County is designated as regulatory 100-year floodplains. Of the 8,000 improved properties located within the floodplain in El Paso County, 42% are situated in unincorporated areas.
 
ISSUE 11.1 encourage Basin-wide Drainage Planning
There is a tendency among property owners, developers and public entities to design solutions which move runoff water off site as fast as possible. Because storm events are infrequent but often intense, public interest in drainage planning issues surface only after storms with significant impact, and therefore, support for drainage studies and improvements is sporadic.
 
Although almost all development activities adversely impact the amount, intensity or quality of stormwater, these impacts are highly variable depending on the type and intensity of development. Therefore, it is difficult to effectively plan drainage improvements unless the ultimate basin-wide land uses are known with reasonable certainty. Often uncontrolled drainage impacts are compounded incrementally, resulting in severe downstream problems and environmental degradation, which in turn are not seen or experienced by upstream contributors.
 
Assuming that adequate land and funding are available, a system which uses regional stormwater detention facilities reduces downstream problems and has the potential advantage of management simplicity. One limitation to this approach is that it does little to address upstream channel degradation. There may also be difficulty in identifying and acquiring sites for regional drainage facilities, especially in previously developed areas.
 
Conversely, a system of smaller on-site drainage facilities potentially can resolve drainage or erosion problems at their source, thereby reducing overall system degradation; however, locations may not be available for on-site systems and maintenance safety issues can be complicated.
While drainage impacts tend to accrue incrementally as development takes place, facilities often need to be constructed in major phases. Timing problems may be further compounded depending upon where development is occurring within a basin. New development increases runoff flow for all downstream structures. Recently constructed downstream drainage structures can quickly become obsolete unless designed to accommodate projected upstream development.
 
Goal 11.1 Promote regional planning and management approaches which protect the integrity of drainage systems and minimize long-term system-wide environmental impacts, costs and recognized flood dangers within the County.
 
Policy 11.1.1
Determine basic design and land requirements in each watershed for drainage facilities at the earliest possible juncture in the planning process to maximize planning options and minimize acquisition and construction costs.
 
Policy 11.1.2
Encourage an approach based on the entire watershed, to flood protection which incorporates a combination of on-site, sub-regional and regional retention and detention facilities to effectively reduce negative downstream impacts including erosion, flooding, channel and water quality degradation.
 
Policy 11.1.3
Set aside the areas needed to accommodate the drainage facilities necessary for full basin build-out.
 
Policy 11.1.4
Require development plans to effectively address both quantitative and qualitative impacts of drainage within the project site.
 
Policy 11.1.5
Effectively utilize automated land use mapping and data management (GIS) to keep drainage basin planning studies current.
 
Policy 11.1.6
Continue to support cooperative multi-jurisdictional approaches to drainage system planning and operations.
 
Policy 11.1.7
Approve site-specific development plans only if there are financial and other assurances that on-site drainage facilities will be appropriately constructed, that downstream infrastructure will accommodate the additional impact, and maintenance issues are fully addressed.
 
Policy 11.1.8
Promote planning approaches which allow for interim solutions for drainage problems in less developed basins.
 
Policy 11.1.9
Support the development of drainage basin management plans which meet the unique needs of rural and rural-residential areas.
 
ISSUE 11.2 consider Funding
The combined costs of on-site and regional drainage system design, land acquisition, and construction significantly contribute to the cost of new development.
 
The average cost for a full drainage basin study is currently $75,000 and may contribute to the difficulty in initiating a study at an early point in the development of a basin.
 
The cost for regional systems alone currently averages about $5,000 per developed acre. Presently there is no dedicated funding source, such as a drainage utility fee, to pay for correcting existing deficiencies or the maintenance which is necessary once facilities are constructed.
 
Goal 11.2 Develop a more equitable and inclusive system for funding the planning, construction and maintenance of regional drainage facilities.
 
Policy 11.2.1
Support the development of drainage funding methods which most equitably allocate costs according to the relative impacts caused by each property.
 
Policy 11.2.2
Promote the development of a dedicated funding source for the operation and maintenance of existing and new regional drainage systems.
 
Policy 11.2.3
Discourage the inclusion of high-cost drainage improvements in drainage basin planning studies (e.g. those which benefit a particular property) unless a system-wide benefit can be demonstrated.
 
ISSUE 11.3 Maximize Environmental Protection and Multiple Use Opportunities
State law requires new subdivisions to maintain regulatory runoff volumes during 100-year events. Many drainage systems are not adequately designed to allow for enhanced runoff resulting from development. Because the enhanced runoff is generally more concentrated and accelerated, the potential for negative impacts to the environment and downstream property owners is significant.
 
Drainage facilities can provide a variety of land use opportunities including open space buffers, preservation of sensitive natural features such as wetlands, ground water recharge zones, natural springs and riparian ecosystems, and can serve as trail, wildlife and utility corridors; however, these same opportunities may become constrained due to safety concerns, lack of maintenance, and environmental degradation. Traditionally drainage corridors have often been viewed by developers and property owners as negative amenities which should be fenced off and obstructed from view. Drainage-ways which are not incorporated into development plans are more prone to accumulations of litter, illegal filling and acts of vandalism.
 
Goal 11.3 Promote the planning and design of drainage facilities which maximize on-site amenities while minimizing detrimental downstream erosion.
 
Policy 11.3.1
Where feasible, support the use of natural or naturalistic drainage approaches rather than hard line solutions.
 
Policy 11.3.2
When possible, safely design and incorporate drainage facilities as an aesthetic element within developments.
 
Policy 11.3.3
Fully evaluate the relative impact of proposed drainage improvements on the maintenance of water quality.
 
Policy 11.3.4
Promote the effective use of innovative short and long term strategies including sediment ponds, buffer strips, and constructed wetlands as a means of reducing peak flows and improving storm water quality.
 
Policy 11.3.5
Protect the integrity of wetlands, riparian areas and associated wildlife habitat through a combination of careful land development and drainage system design.
 
Policy 11.3.6
Encourage the effective use of control measures to mitigate the short and long term erosion impacts of development.
 
ISSUE 11.4 Reduce Flood Danger
Reasonable alternatives for addressing existing structures which are located in the flood plain are limited; however there are a number of engineering, regulatory and warning systems approaches which can partially mitigate this danger and potential for financial loss.
 
Planning for flood protection while reducing flood danger is a challenge because flood-prone areas are extensive and actual floodplain boundaries are subject to change due to channel migration caused by erosion. Rates of bank erosion may be accelerated as a result of upstream development activities and result in changes to the FEMA the Regulatory 100-year Flood Plain designation.
 
Additional development within floodplain areas increases risk of loss and impedes the ability of drainage channels to convey stormwater. However, the strictest interpretation of floodplain regulations may severely limit the use of private property.
 
Goal 11.4 Promote public safety and reduce loss of private property.
 
Policy 11.4.1
Strongly discourage land use development from locating in designated floodplains.
 
Policy 11.4.2
Strongly discourage land use development from locating in areas below dams, spillways, and levees that would require the State Engineer to upgrade the classification of these structures.
 
Policy 11.4.3
Encourage the removal of existing structures within the flood-plain when this can be accomplished in a cost-effective and equitable manner.
 
Policy 11.4.4
Support the construction of facilities which will protect existing structures in flood-prone areas if this can be accomplished in a manner which is environmentally sensitive and will not significantly reduce the ability of the floodway to carry peak flows.
 
Policy 11.4.5
Support the continued refinement and use of regional flood warning systems.
 
Policy 11.4.6
Continue to encourage the disclosure of flood hazards to current and future property owners.
 
Policy 11.4.7
Limit new development in and modification of flood plains in accordance with regionally adopted flood-plain regulations.
 
Policy 11.4.8
Encourage "prudent line" approaches which adequately set structures back from flood-plain boundaries, especially in areas which may be prone to bank erosion.
 
Note: Drainage policies and requirements are set forth in Drainage Criteria Manual the City of Colorado Springs and El Paso County. This document currently advocates the use of large regional detention basins rather than smaller facilities.
 


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