Marshall Ora Leighton

“ Powerville reservoir.—A short distance above Boonton the erection of a comparatively small dam would flood a large, irregular, flat basin having an area of a little more than 4-1/2 square miles and extending up the Rockaway Valley to Rockaway Village, up Beaver Brook to Beech Glen, and north and south for considerable distances. The probable capacity of this reservoir has been estimated, and it is fairly certain that it is considerably more than would be sufficient for flood catchment. Its construction would, moreover, improve the entire valley and be of advantage to many interests. ”

“ It is therefore better, wherever possible, to provide a reservoir capacity considerably larger than that represented by the run-off from the heaviest storms, so that water may be stored for use as power or domestic supply. With such provision it is necessary merely to draw from the reservoir water to a depth equivalent to the stream run-off in the drainage area above. ”

“ Population in the valley of the Passaic is developing so rapidly that in only a few years the present sources of water supply will be inadequate. The whole subject of water supply for northern New Jersey demands immediate consideration, and it would not be wise to take up the matter of prevention of flood damage in the Passaic without [Pg 44] basing the value of every project upon its adaptability for use in future water-supply needs.
By expending $2,600,000 a great reservoir could be constructed upon Great Piece Meadow which could not be adapted for any purposes except to regulate floods ”

“ The Mountain View site is an ideal one for the reservoir, and its initial development for flood catchment does not involve the expenditure of a dollar that would be lost in the development of the basin to greater capacities for water supply. From its lowest level, at 202 feet above tide, to its maximum capacity, at a level of 220, there would be no depreciation. Every dollar spent in the initial construction would be effective in the maximum development. ”

“ Little benefit would be derived from such a reservoir, as the limited drainage area affords a comparatively small proportion of flood run-off that might be well cared for at a lower point. For compensating purposes, however, a reservoir might be constructed here, the capacity of which could be adjusted to the actual demands. If the dam were raised to a height of about 280 feet from the base the storage afforded would be equal to 176 inches on the watershed, or about four average years of precipitation, which is far beyond all probable storage necessities. ”

“ It differs materially from destruction by fire, for often destructible property is of value after floods have passed. Buildings which are inundated still retain value, and many kinds of merchandise are not totally destroyed. Therefore when the amount of damages is calculated there is always to be taken into consideration the fact that a part of the material which has been flooded can be reclaimed, and retains some proportion, at least, of the value which it had previously possessed. Furthermore, damages by flood enter into practically every detail of social and business affairs. ”

“ It is generally estimated that 25 per cent of the volume of the mean annual rain on a given catchment is sufficient reservoir capacity to fully utilize the flood flows. We have long series of observations of rainfall at three points, which may be taken to fairly represent the Passaic catchment. At Newark the mean annual rainfall is 46.2 inches, at Paterson, 50 inches, and at Lake Hopatcong, 42. The last being on the Highlands, like most of our watersheds, is perhaps the safest to use. ”

“ This point has been considered an excellent site for the construction of a dam, and in the installation of the present water-supply system of Newark it is proposed that the entire valley in which Newfoundland is situated be overflowed. The site is one of the most advantageous known for the creation of a flood-catchment basin. If a dam 50 feet high were erected across this gorge, a lake would be formed which would have a surface area of 3.15 square miles and a capacity of 3,267,200,000 cubic feet, equal to a storage of about 30.5 inches on the 46.12 square miles of contributing drainage area. ”

“ There are losses which are severe to one or more persons, and which can not be appreciated except by those whom the floods have actually overtaken. Therefore estimations of flood damages can be only approximate, and while a measure of accuracy may be reached with respect to a part of the losses, there remains a necessity for approximation which can not be classed with carefully computed damages along other lines. ”

“ There are few available reservoir sites of large size along the lower reaches of Pequanac River. In the upper basin, however, there is a sufficient available storage capacity to afford almost complete control of destructive floods from that part of the drainage area. Large tracts are already reserved by the city of Newark for collection of municipal supply, and the storage capacity developed is sufficient to serve the city throughout the driest seasons. ”

“ The effectiveness of a reservoir built upon the lines proposed in the case of Great Piece Meadow depends upon the adjustment of outflow so that the channel below will not be overborne, while at the same time sufficient storage capacity is afforded to hold temporarily the water which enters above the dam in amount greater than the carrying capacity of the outflow apertures. The dam across Passaic River above Little Falls would be provided with apertures which would discharge 12,000 cubic feet per second under the maximum head in the storage basin. ”

“ The second plan for prevention of flood damages involves provisions for letting the flood water out rapidly by removing obstructions to its flow by straightening and deepening the channels and providing long embankments, dikes, or levees which rise above the ordinary river level to a height exceeding that of the stream during its highest floods. ”

“ There are in the Pompton system several sites on Ramapo, Wanaque, and Pequanac rivers which, if utilized, would afford sufficient storage for flood catchment purposes, but the entire flow of the river system may be conserved in what has been described as the Pompton reservoir. ”

“ It occurred before the time of the maximum gage height at the mouth of Pompton River, and there is nothing to indicate that it was caused, as has been claimed, by slack water from the Pompton flood being forced back into Great Piece Meadows. There is no doubt that a part of the Pompton flood was so diverted, but there was maintained throughout at Little Falls a steady pressure, which constantly increased to maximum. This flood check, at Dundee dam was observed in 1902, but it could not be shown to arise from the frequently mentioned phenomena at the mouth of Pompton River. ”

“ So that, all things considered, the prevention of flood damages in the Passaic Basin can be best accomplished by a combination of the two general methods above outlined.
LOWER VALLEY IMPROVEMENTS.
The channel of Passaic River below Great Falls, at Paterson, is of limited capacity. To anyone making an inspection, especially within the city of Paterson, it is readily apparent that the river bed has for years been considered a legitimate field for encroachment. Owners of lands fronting on the river have increased their holdings by filling in beyond the channel line. ”

“ Flow of Passaic River at Dundee dam, 1903.
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DAMAGES. GENERAL STATEMENTS.
Estimates of flood damages are always approximations only. It is possible to determine with a fair degree of assurance the cost of replacing structures which have been carried away, to estimate the value of goods destroyed—especially if they be commodities stored in shops or warehouses—to calculate the amount of operatives' wages lost, and in the case of general mercantile business to estimate the damages incurred through consequent reduction of trade. Destruction by flood, however vast, is incomplete. ”

“ The opportunity for varying the character of the reservoir to meet the ideas of those interested seems unexampled, and as a whole it presents an extremely interesting field which may be profitably exploited. ”

“ For flood purposes alone it would be necessary to provide reservoirs of sufficient capacity to contain the run-off waters resulting from the largest storms. With such provisions it would be necessary to entirely empty the reservoir as soon as possible after a storm had passed and leave its full capacity available for the next storm. ”

“ So sudden a decrease in the effectual height of the dam must lower the water on the dam crest markedly, and as every other probable cause has been eliminated in the case of the recent flood, the explanation of the check in the progress of floods over this dam may be safety accepted as due to carrying away of flashboards. ”

“ From the above tables it may be seen that the maximum rate of precipitation per hour was 1.38 inches at New York and 1.2 inches at Newark. Comparison of the tables on pages 11 and 12 gives an excellent idea of the intensity of the storm. The amount of water falling in a single storm is nearly equal to the total for June, a month of unusual precipitation. ”

“ There are, nevertheless, several things to be taken into consideration, the most important of which are the improvements which have been made by wealthy residents along the valley where it has already been developed as a summer resort. ”

“ It is impossible to secure correct figures, because merchants and manufacturers refuse to give details of losses, fearing that the publication thereof would affect their credit. General ideas concerning the destruction by the flood can be gathered from Pls. I, B, III, IV, V, and VI.
Passaic and vicinity.—Below the city of Paterson destruction was as complete as in Paterson, although the damage was not as great because the improvements were not as valuable. Damage to property, exclusive of public works, in this region, amounted to about $1,250,000. ”

“ WS 61. Preliminary list of deep borings in the United States, Pt. II, by N. H. Darton. 1902. 67 pp.
WS 67. The motions of underground waters, by C. S. Slichter. 1902. 106 pp., 8 pls.
B 199. Geology and water resources of the Snake River Plains of Idaho, by I. C. Russell. 1902. ”