FLOOD07908

• Designation Number: 260
• County: Jefferson
• Community: Unincorporated Jefferson County
• Basin: South Platte
• Title: Major Drainageway Planning - Sanderson Gulch/Weir Gulch Volume I
• Date: 8/1/1972
• Designation Date: 12/1/1987
• Floodplain - Doc Type: Floodplain Report/Masterplan

:umORA~Dr;:.1

The~e res~onses to essentially private disputes present a
pair of legal principles which are somewhat cross-grain to
each other from the point of view of the District in its role
as manager-planner of flood and drainage matters. On the one
hand, it is important for the natural drainage "easement"
concept of the Ambrosio case to be preserved as a fundamental
principle on WhLCh flood plain zoning and flood channel manage-
ment is based. On the other hand, a realistic limit on t~e
allowable amount of runoff due to urbanization nceds to be
enforced so that the duty of upstream owners to help pay the
costs of urban drainage is made clear. It is the former of
these principles that will primarily concern us in this study.

TO:

Frasier & Gingery" Inc., Consulting Engineers

FR0I1,

Raphael J. Moses, Attorney at Law

DATE:

January 26, 1972

RE:

Legal Aspects of the Drainage Study of Sanderson and Weir
GulChes in the ~rban Drainage and Flood Control District,
Colorado

FACTS

INTRODUCTION

There are numerous different conditions along the existing
Sanderson and Weir Gulch channels which present manage~ent
problems. Five of these in particular, however, give rise
to important legal questions. These are enumerated below:

The essential problem presented in the case of both Weir and
S~nderson GulChes is that of maintaining existing drainage and
flood protection capabilities. To this end we explore herein
certain aspects of flood plain zoning, enforcement of reservoir
safety requirements by the State Engineer, and less-than-fee
acquisition of existing flood detention structures.

1. Ma;or IrrigatiOn ComPany Storaqe Reservoirs
Typical of this situation are three large reservoirs owned
by the Agricultural Ditch and Reservoir Company located in
the upper reaches of Sanderson and Weir GulChes, Main
Reservoir, East Reservoir and Smith R~servoir. They are
operated and maintained solely for irrigation supply
pUrpos~s and thus may either have SUbstantial drawdowns
or may be nearly full at the time of a flood occurrence.
However, they are large in surface area, and a small rise
in the water height represents a large volume of temporary
flood storage. The basin above these is small in ~rea,
and under most conditions these reservoirs would totally
retain the flood at that point.

Foundation work analyzing the basic principles of liability for
flood and drainage damage has been done by prior studies for the
Denver Regional Council of GovernmentS. Urban Storm Drainage
Criteriil Milnual, Summary of Colorndo Drainage Law (1969); W. J.
Shoemaker, Legal Aspects of Proposed prainaie Improvements,
NORTH BOULDER ~~JOR DRAINAGEWAYS lIT-PORT, Vo . 1, Sect10n 5
(Apr11, 1969). The essentlal doctr1ne described is that in
ColoradQ underlying OWnerS along a natural drainage channel havu
d duty to accept the storm runoff from upstream lands, even when
there has been some increilse in flow due to urbanization, Ambrosio
v. Perl-Milck Constr. Co., 143 Colo. 49, 351 P.2d 803 (l%O). It
'""ould apr,>ear ObVlOUS that th!'re is some limit to the "mount of
increased flow that mu~t be toleruted, Hankins v. Borland, 163
Colo. 575, 4]l P,2d 1007 (1967). However, there has not been
a clear casu in Colorado dealing with the duty of upstream owners
to provide for their own increases in runoff when extc~5ive
urbanization has effectively appropriated all the available
storm flow capacity of the natural channel, and overtopping and
extra-channel damage has become unavoidable. It seems inevitable
that t:,e upstream owners must accept responsibility for this
runoff, Shocm~ker, A~ E~ ineerin -Le al Solutio~ to Urban
Drainage Problems, 45 Oenver Law Journa 381 1968.

East Reservoir is particularly proble~tic. It is struc-
turally the least dependable. Because it does not have
a large, stable spillway and has vury little freeboard,
its U5e even for temporary storage may, after engineering
analysis, prove to be hazardous. We understand there is
some agreement between the developers of the underlying
urban area and the owners to maintain two feet of freeboard
to give a marginal amount of protection. On thc day of the
on-site inspection, however, it appeared that there was less
than this amount of freeboard, although icy conditiOnS made
this judgment difficult to make. The natural channel belOW
both East and Main reservoirs has been obliterated by the
downstream urban development, and even if spillway structure5

2