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DRAINAGE
AND FLOOD CONTROL (DR)
VISION
STATEMENT
Planning
for drainage and flood control facilities in the Tri-Lakes
Area will result in an integrated system that addresses
long-term costs, minimizes overall environmental impacts
and provides community value in the areas of aesthetics,
natural systems preservation, recreational and trail opportunities.
GUIDING
PRINCIPLES
-
Protect
the public, private property, and public investments
from potential hazards due to flooding.
-
Ensure
planning and implementation of a system-wide approach
to drainage and flood control.
-
Consider
the dual potential for drainage and flood control
facilities to function as parks, trails and/or open
space.
Photo:
Monument Lake
BACKGROUND
Many of the streambeds, valleys, and flood plains in Tri-Lakes
are naturally dynamic and unstable due to compacted heavy
clay soils, precipitous topography, sometimes infrequent
but intense storms, and semi-arid climatic conditions.
Approximately seven percent (7%) of the planning area
is currently within the regulatory 100-year flood plain*
as designated by FEMA**. In addition to the natural conditions,
as new development takes place naturally occuring permeable***
surfaces are replaced by impervious surfaces . Impervious
surfaces, such as roofs, paved driveways and parking lots,
increase and concentrate stormwater runoff contributing
to increased erosion, siltation, stream channel degradation,
and lessening of surface water 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.
Floodplain
management in El Paso County is subject to federal mandates
and is largely a function of the Floodplain Administrator,
which is coordinated through the Pikes Peak Regional Building
Department. The City/County Drainage Board makes recommendations
to City Council and the BOCC regarding credits and reimbursement
issues with new development. Currently the Towns of Monument
and Palmer Lake do not participate in this regional planning
effort but each has its own guidelines. Map TR.1 indicates
the drainage basins that have been studied.
The
emergency flood hazard study was completed in 1977 by
the Federal Emergency Management Agency (FEMA) to determine
flood insurance rates and the County is eligible for Regular
Program coverage. The basis for this eligibility was the
culmination of more detailed studies:
- stream
gauging data with peak discharge rates and
- stream
cross sections.
Table
DR.1: Identified Flood-prone Areas
- Beaver
Creek
- Crystal
Creek
- Dirty
Woman Creek
- Hay
Creek
- Jell
Creek
- Jackson
Creek
- Monument
Creek
- Smith
Creek
- West
Cherry Creek drainageways
- Butler
Canyon (located in Palmer Lake)
- Carpenter
Creek (located in Palmer Lake)
Economic,
political, and market pressure make some development on
floodplains inevitable. However, appropriate planning
and subdivision design can minimize risks of flood damage,
or eliminate them entirely. Streams, floodplains, and
topographic features, influence the physical layout of
a community. The way in which communities incorporate
these features will in part influence every other physical
aspect of development.
Responsibility
for construction and maintenance of drainage facilities
in the unincorporated areas has traditionally been shared
by individual property owners, developers, and the County
Department of Transportation. While many of the public
facilities that are constructed to handle drainage are
located within areas designated as 100-year floodplain,
this system extends throughout the basin in the form of
road side ditches and swales, storm drains and curb and
gutter. A regional fee system using a basin-wide planning
approach has been developed for 30 of the drainage basins
in the City and County and fees have been previously calculated
on a per-acre basis. A new method has been implemented
in the County which relates the fee to impervious area,
such that the fee is reflective of actual impact. This
approach is applied in studied basins and areas experiencing
higher rates of growth.Fees are only collected at the
platting stage, if they are not waived.
At
this time, drainage fees do not cover the cost for necessary
infrastructure improvements or for the maintenance of
drainage facilities once they are in place. . This fee
structure has been recalculated in basins with studies
to account for variations in lot size, type of land use,
and the area of land covered by impervious surfaces. .
Alternative funding methods for existing drainage infrastructure
and improvementsa are being considered by a regional task
force.
ISSUE
DR.1 DRAINAGE PLANNING
Currently, the Towns of Monument and Palmer Lake
do not participate in regional drainage planning efforts.
Although both jurisdictions have their own standards,
which are in many ways as good or better than the established
regional standards, it is difficult to comprehensively
plan for drainage improvements when not all the players
are participating in the planning process. It is critical
for good stormwater management that all jurisdictions
coordinate to produce basin planning studies. A study
should be completed for every basin in the watershed.
There
is a tendency among property owners, developers and public
entities to design and approve drainage solutions that
do not consider impacts to downstream properties. The
older philosophy was to move water off-site and downstream
as fast as possible, often, much to the chagrin of downstream
neighbors. This approach to drainage may be short-sighted
in that it ignores the potential benefits of stormwater
runoff. Rather than creating drainage solutions, concentrated
stormwater run-off accelerates and intensifies flow and
downstream problems. As these problems intensify, they
become more costly and unmanageable. When drainage impacts
are uncontrolled, they compound incrementally, resulting
in severe downstream environmental degradation with high
risk to property, public health and safety.
In
contrast, stormwater improvements, such as detention ponds
and landscaping, while adding to the overall cost of development,
can be attractive and contribute to the value of the property.
Detention facilities when planned in conjunction with
low-level water consumptive landscaping, such as xeriscaping,
can also significantly reduce the cost for irrigation.
As with any type of landscaping or parking facility, stormwater
improvements are subject to periodic maintenance. However,
when detention is utilized for the purpose of flood control,
it should be designed and implemented on an overall basin
approach, per the planning study recommendation. While
detention/retention does reduce peak flow rates, there
is still an increase in volume of runoff which over time
results in greater downstream impacts.
In
subregional approaches to stormwater management, the capacity
of each drainage basin is studied. A number of these studies
have been developed for drainage basins within the Tri-Lakes
Area (see Map DR.1). Both on-site and off-site detention
solutions within a defined drainage basin are often proposed
in an effort to maintain the integrity of the overall
watershed by minimizing downstream erosion, siltation,
and degradation. Since all development occurs within a
watershed, the type and density of land use, the runoff
coefficient, and the way it situated on the site, all
contribute to the dynamics of the drainage basin.
In
many communities, parks, trails, and open space are planned
in association with drainage and flood control. Due to
the infrequency of storms, these facilities normally serve
as community greenways. The natural surfaces absorb some
of the water and slow down the rate of runoff, ultimately
reducing the overall impact and downstream degradation.
Smaller
on-site detention and drainage facilities can greatly
resolve drainage and/or erosion problems at their source,
thereby reducing overall impact to the basin-wide system.
On-site drainage systems can be designed as a site amenity
but system maintenance and safety issues must also be
addressed. While drainage improvements might add to the
cost of development, these costs are often offset by savings
in enhanced visual appeal. Smaller on-site detention and/or
drainage facilities can help to greatly reduce the overall
requirement for basin-wide drainage facilities. However,
disadvantages of smaller facilities are that they are
more difficult or problematic to maintain and they may
not fully handle the impact of a large storm event.
Basin-wide
drainage facilities are generally constructed in major
phases depending on when and where development will occur.
Given this scenario, even recently constructed downstream
drainage structures can quickly become overburdened unless
designed to accommodate future projected development.
GOAL
To promote comprehensive planning and management
approaches to preserve or improve the integrity of the
drainage basins within the planning area and minimize
long-term system-wide environmental impacts.
Photo:
Summer 1999 Courtesy: Andy de Naray
OBJECTIVES
DR.1.1
Study the drainage basins to determine the improvements
necessary to meet projected growth in the planning area.
DR.1.2
Encourage opportunities to include the Towns of Monument
and Palmer Lake in future regional stormwater and drainage
comprehensive planning efforts.
DR.1.3
Consider and adhere to the recommendations in the existing
drainage basin planning studies.
DR.1.4
Encourage a comprehensive approach to flood protection
and drainage, that incorporates retention and detention
facilities to reduce soil erosion, channel degradation,
and flooding, while at the same time contributing to improvements
in water quality.
DR.1.5
Identify in Basin Planning Studies and any other land
use documents where appropriate, require dedication of
the areas necessary to accommodate drainage facilities
for full basin build-out.
DR.1.6
Consider a system of parks, trails, and open spaces that
could also serve as a drainage and flood control system
to slow the rate and reduce the intensity of stormwater
runoff.
DR.1.7
Discourage modification of floodplains.
DR.1.8
Promote Best Management Practices in an effort to prevent
and/or significantly reduce problems associated with stormwater
runoff and erosion.
PROPOSED
ACTIONS
DR
1.9 Equitably assess the costs for drainage basin
planning and improvements.
DR
1.10 Where possible, incorporate parks, trails,
and open space as natural elements to reduce the rate
of stormwater run-off.
DR
1.11 Require development plans to realistically
address drainage and adhere to the criteria found in the
City/County Drainage Criteria Manual. Where feasible,
and when in compliance with planning studies, require
on-site detention of developed stormwater runoff.
DR
1.12 Require, monitor, and enforce erosion control
plans to prevent sediment from running onto adjacent properties
and/or into drainage channels.
DR
1.13 Amend the El Paso County Land Development
Code and/or Subdivision Criteria Manual to include Best
Management Practices for drainage system planning and
design.(currently in progress)
ISSUE
DR.2 FUNDING
The
combined costs for on-site and subregional drainage system
planning, design, land acquisition, and construction can
significantly contribute to the cost of new development.
A
number of basins have been studied in the Planning Area
(see Map DR.1). The average cost for a full drainage basin
study is currently in excess of $75,000 and may be a limiting
factor in initiating a study at the early point in the
development of a basin. The drainage fees assessed when
a property is subdivided in studied basins currently averages
about $5,000 per developed acre. All revenues collected
go toward reimbursing developers and property owners for
the cost of the facilities they have constructed in excess
of their obligations. Presently, there is no dedicated
funding source, such as a drainage utility fee, to pay
for correcting existing deficiencies and for the on-going
maintenance of these facilities which becomes necessary
once they are constructed.
GOAL
To develop an equitable system for planning, funding,
constructing and maintaining drainage facilities.
Photo:
Summer 1999 at Knollwood Drive Courtesy: Dave Root: Monument
Tribune
OBJECTIVES
DR.2.1
Support the development of drainage funding methods which
most equitably allocate costs according to the relative
impacts caused by each property.
DR.2.2
Promote the development of a dedicated funding source
for the operation and maintenance of existing and new
regional drainage systems.
DR.2.3
Encourage that stormwater impacts be mitigated by installation
of downstream facilities or detained on-site until normal
regulatory runoff flows are achieved.
DR.2.4
Discourage new development and land use practices that
divert drainage and associated problems to surrounding
properties.
DR.2.5
Discourage construction practices that do not confine
erosion on the development site.
ISSUE
DR.3 ENVIRONMENTAL PROTECTION
State
law requires new subdivisions to maintain historic runoff
volumes where discharge leaves their site.Local drainage
criteria design is based upon 10 year and 100 year recurrence
interval criteria Currently many drainage systems are
not adequately designed to meet this requirement. However,
even in cases where historic flow rates are maintained,
the cumulative effect of additional flow over time will
contribute to a long-term adverse impact on stream corridors.
Both
improved and natural channels are often perceived as negative
features that should be obstructed from view. Drainage-ways
that are not incorporated into developments as amenities,
or are not easily visible, tend to become public nuisances
as they accumulate litter and become more prone to crime
and vandalism.
Drainage
facilities can provide a variety of land use amenities.
Monument Lake is a good example of a retention reservoir
built in the 1890's to store water. It also has the potential
to reduce downstream flooding in the Monument Creek drainage
basin. Athletic fields can also serve as water detention
facilities and the need for them has been identified in
the community.
GOAL
To promote the planning and design of drainage facilities
which maximize on-site amenities while minimizing downstream
erosion and other problematic activity.
Photo:
Stocking Fish in Monument Lake Courtesy: USAF Academy
OBJECTIVES
DR.3.1
Support the use of natural or naturalistic drainage approaches
that allow for secondary recreation purposes, rather than
paved, hard-surfaced drainage channel solutions that only
serve one purpose and tend to become public nuisances.
DR.3.2
Support incorporating safely designed drainage facilities
that can serve as both functional and aesthetic elements
within developments.
DR.3.3
Fully evaluate the relative impact of proposed drainage
improvements including the resulting water quality and
the on-going requirement to maintain the improvements.
DR.3.4
Protect the integrity of wetlands, riparian areas and
associated wildlife habitat through a combination of careful
land development and drainage system design.
PROPOSED
ACTIONS
DR.3.5
Require proven types of erosion control measures to mitigate
the short and long term erosion impacts from development.
DR.3.6
Mitigate the loss of significant wildlife habitat caused
by the impacts of development within wetlands and/or natural
drainageways. Areas with wildlife habitat and wetlands
should remain undisturbed or mitigated with an area greater
than the area disturbed.
ISSUE
DR.4 FLOODING
Development
within floodplain areas increases the risks to safety
or loss of life and property and impedes the ability of
drainage channels to convey stormwater. Reasonable alternatives
for addressing existing structures which are located in
the floodplain are limited due to water rights law and
available land to build structures. 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 is a challenge because flood-prone
areas are extensive and actual floodplain boundaries are
subject to change due to channel migration caused by erosion
and development. Rates of bank erosion may be accelerated
as a result of upstream development activities and result
in changes to the FEMA Regulatory 100-year floodplain
designation. -
GOAL
To promote public safety and reduce loss of property.
OBJECTIVES
DR.4.1
Consider establishing a drainage and flood control overlay
protection zone, or utilize a "Prudent Line"
approach for all 100-year floodplains.
DR4.2
Prohibit or appropriately limit development of homes,
schools and hospitals in the overlay protection zones
per a prudent line setback, or erosion setback. Consider
only development such as parks, trails, and/or open space,
with a very low risk for human health and safety that
will not accelerate runoff rates or adversely effect the
overall environmental quality of the drainage basins.
DR.4.3
Require the on-going maintenance of dams.
DR.4.4
Prohibit development from locating in areas below dams,
spillways, and levees that would require the State Engineer
to upgrade the classification of these structures.
DR.4.5
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.
DR.4.6
Support development and use of regional flood warning
systems.
DR.4.7
Encourage "prudent line" approaches which adequately
set structures back from flood-plain boundaries, especially
in areas which may be prone to bank erosion.
PROPOSED
ACTIONS
DR.4.8
Establish guidelines for appropriate low-impact land uses
in floodplains that do not threaten public health, safety
and welfare. Current regulations should continue to be
enforced so that such uses as primary residences, hotels,
hospitals, nursing homes, schools and other uses that
have a high potential for damage to property and/or to
human life during an emergency will not be located within
the 100-year floodplains.
DR.4.9
Require the disclosure of flood hazards to current and
future property owners.
DR.4.10
Limit new development in and modification to flood plains,
spillways, and valley bottoms. Require strict adherance
to local floodplain regulations and subdivision criteria.
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.
_________________________
*
Floodplain information is from Charles S. Robinson &
Associates, Inc. 1977 GIS coverage.
**FEMA
Federal Office of Emergency Management Administration,
an office which among other things, administers federal
floodplain regulations and programs.
***Permeable
Surfaces:
Natural surfaces that allow water to penetrate or pass
through the porous soils.
****Impervious
Surface Coefficient
The percentage of the entire area within a given development
or drainage basin which is or is anticipated to be covered
by man made impenetrable surfaces including but not limited
to roads, driveways, parking lots, roof tops and sidewalks.
*****Watershed:
An area of land that has a defined boundary where water
flows from the upper elevations to a defined steam or
lake in the lower elevations.
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