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<br />:umORA~Dr;:.1 <br /> <br />The~e res~onses to essentially private disputes present d <br />pair of legal principles which are somewhat cross-grain to <br />each other from the point of view of the District in its role <br />as manager-planner of flood and drainage matters. On the onc <br />hand, it is important for the natural drainage "easement" <br />concept of the Ambrosio case to be preserved as a fundamental <br />principle on WhLCh flood plain zoning and flood channel manage- <br />ment is based. On the other hand, a realistic limit on t~e <br />allowable amount of runoff due to urbanization needs to be <br />enforced so that the duty of upstream owners to help pay the <br />costs of urban drainage is made clear. It is the former of <br />these principles that will primarily concern us in this study. <br /> <br />TO: <br /> <br />Frasier & Gingery" Inc., Consulting Engineers <br /> <br />FR0I1, <br /> <br />Raphael J. Moses, Attorney at Law <br /> <br />DATE: <br /> <br />January 26, 1972 <br /> <br />RE: <br /> <br />Legal Aspects of the Drainage Study of Sanderson and Weir <br />GulChes in the ~rban Drainage and Flood Control District, <br />Colorado <br /> <br />FACTS <br /> <br />INTRODUCTION <br /> <br />There are numerous different conditions along the existing <br />Sanderson and Weir Gulch channels which present manage~ent <br />problems. rive of these in particular, however, give rise <br />to important legal questions. These are enumerated below: <br /> <br />The essential problem presented in the case of both Weir and <br />S~nderson GulChes is that of maintaining existing drainage and <br />flood protection capabilities. To this end we exploro herein <br />certain aspects of flood plain ~oning, enforcement of reservoir <br />safety requirements by the State Engineer, and less-than-fee <br />acquisition of existing flood detention structures. <br /> <br />1. Maior Irrigation ComPany Storaqe Reservoirs <br />Typical of this situation are three large reservoirs owned <br />by the Agricultural Ditch and Reservoir Company located in <br />the upper reaches of Sanderson and Weir GulChes, Main <br />Reservoir, East Reservoir and Smith Reservoir. They are <br />operated and maintained solely for irrigation supply <br />purposes and thus may either have SUbstantial drawdowns <br />or may be nearly full at the time of a flood occurrence. <br />However, they arc large in surface area, and a small rise <br />in the water height represents a large volume of temporary <br />flood storage. The basin above these is small in area, <br />and under most conditions these reservoirs would totally <br />retain the flood at that point. <br /> <br />Foundation work analyzing the basic principles of liability for <br />flood and drainage damage has been done by prior studies for the <br />Denver Regional Council of Governments. Urban Storm Drainage <br />Criteriil Milnual, Summary of Colorndo Drainage Law (1969); W. J. <br />Shoemaker, Leqa1 Aspects of Proposed prainaie Improvements, <br />NORTH BOULDER ~~JOR DRAINAGEWAYS lIT-PORT, Vo . 1, Sect10n 5 <br />(Apr1l, 1969). The essentlal doctr1ne described is that in <br />ColoradQ underlying oWners along a natural drainage channel havu <br />d duty to accept the storm runoff from upstream lands, even when <br />there has been some increase in flow due to urbanization, Ambrosio <br />v. Perl-Mi.lck Constr. Co., 143 Colo. 49, 351 P.2d 803 (1%0). It <br />''''auld apr,>ear ObV10US that th!'re is some limit to the amount of <br />increased flow that must be tolerated, Hankins v. Borland, 163 <br />Colo. 575, 4]1 P.2d 1007 (1967). However, there has not been <br />a clear case in Colorado dealing with the duty of upstream owners <br />to provide for their own increases in runoff when extensive <br />urbanization has effectively appropriated all the available <br />storm flow capacity of the natural channel, and overtopping and <br />extra-channel damage has become unavoidable. It seems inevitable <br />that t:,e upstream owners must accept responsibility for this <br />runoff. Shoemaker, An En ineerin -Le al Solution to Urban <br />Drainage Problems, 45 Denver Law Journa 381 1968. <br /> <br />East Reservoir is particularly prob1e~tic. It is struc- <br />turally the least dependable. Because it does not have <br />a large, stable spillway and has very little freeboard, <br />its use even for temporary storage may, after engineering <br />analysis, prove to be hazardous. We understand there is <br />some agreement between the developers of the underlying <br />urban area and the owners to maintain two feet of freeboard <br />to give a marginal amount of protection. On thc day of the <br />on-site inspection, however. it appeared that there was less <br />than this ~mount of freeboard, although icy conditions made <br />this judgment difficult to make. The natural channel belOW <br />both East and Main reservoirs has been obliterated by the <br />downstream urban development, and even if spillway st~uctUres <br /> <br />2 <br />