DRAINAGE OF SWAMPS.

Hauraki Plains Gazette, Volume XXXII, Issue 4349, 30 November 1921, Page 3

DRAINAGE OF SWAMPS.

METHODS IN AMERICA. COMPARISON WITH DOMINION ENGINEER'S SUGGESTION. ,

Land drainage methods in the United Stated and Canada is the subject of a. reporti presented to Parliament by the chief! engineer of the

Land and Survey Department, Mr J

B. Thompson, who, between May, 1920, and Maijch - last visited those two countries to inquire into the latest methods of land drainage in practice there, and alsp to select suitable up-to-date plant ter prosecuting, similar work in New Zealand. Mi’ Thompson states that in Canada ; he had the opportunity of inspecting . levee works Fraser River, British Columbia ; drainage of irrigated lands in Alberta; gumbo lands in Manitoba, and operations being conducted on peaty country in Ontario. All this was being carried out by dipper dredges, walking dippers, . and drag,-line excavators. Very excellent work was being done, but none of it under conditions as wet as those which usually prevail in Nexy Zealand. Maintenance, he states, is more or less a dead letter, and the authorities informed him is still an unsolved problem. For the construction of all classes of .large ditches hand labour has been superseded by machinery. Special facilities were afforded him oU seeing the work of several dipper and clam-shell dredges operating at Toronto and Montreal, but <hese machines were generally too large for operations in this Dominion. In the United States Mr Thompson, inspected drainage operations in no ~ fewer than 15 States, and found that very great importance was attached to bringing to profit all flooded and swamp lands. IQ is recognised in the United State's, as it is in New Zealand, that probably the “richest land is to be found in swamp areas. < Important Data Available. “My observations, as regards respective qualities,” states Mr Thompson, "convinced me that there is no better swamp area in America than can be found in New Zealand; but the area in the former country is quite staggering. In .the United States the wet areas are approximately as follows ; Swamp, 66,000,000 acres ; periodically.; overflowed, 31,000,000 acres; tidal marsh’, 4,000,000 acres. Probably three-fourths of these lands are timbered, and in many instances cut over.” The general practice in considering a new project in either country, observes Mr Thompson, is tjhat extensive engineering surveys am! other necessary details are called for, and it is only after deliberate analysing of . all information and finance proposals that a decision is arrived at on the question of proceeding with the work. In the United. States much of the way is cleared for the drainage engineer, as practically the whole of the States are covered by meteorological and .hydrographic surveys. The precipitation, run-off, . gauging of all streams, their velocities, etc., are available, and thus a drainage coefficient is at once known for a particular district. This points markedly to the disadvantages engineers in New Zealand labour under, due' to a complete absence of systematic observations of precipitation and run-off. Flood discharges of local rivers and streams are, ihe states, sadly wanted, and can only be arrived at under largely supposititious conditions, and the employment of formulae which lead to indifferent approximation. Actual observations extending .over a period of years are essential. Tp assist the land drainage branch of the department several flow-recorded and current meters have been secured and will be landed shortly. Comparing the "muck” and "peat” soil in the United States witjh that in New Zealand, Mr Thompson states that in Minnesota, Wisconsin, Michigan,- and Florida are to be seen considerable areas similar to those in the Dominion. 'No Richer Swamp Than Hauraki.

“The Everglades, Florida, bear a close resemblance- to the Hauraki Plains/’ says the .report, “but are enormous in area, comprising some 5,000,000 acres. One feature is quite distinct, though', and this is the substratum of coralline limestone. New Zealand is fortunate in pot having this substratum, but in place thereof clay of varying quality. The peat depths seen in several States are much shallower than in New Zealand, and range from a few inches to iOft.” These genuine swamp areas are classed 'as "muck” and “peat,” the former containing a fair proportion of silt, while the latter is pure vegetable matter.' Roth characteristics can be seen in most New Zealand swamps. A conclusion -is arrived at that the "muck” and “peati” soils of both countries are similar in character and productivity, but tlhat much better pasture can be seen on the drained swamp areas of New Zealand. Acre for acre, the American swamp lands are no better drained nor responsive than those of-New Zealand. No land was seen in the United States of America to exceed in quality that of the alluvial swamp areas of New Zealand, and tjhe Hauraki Plains area, together with Rangitaiki Plains, stand out as object lessons in the way of both pasture and stock-carr.y- -■ ing capacity. Much attention is given to the question of the water-table in swamp lands, and exhaustive experiments are being continuously carried out as to point of saturation, etc. It is recommended that this field be explored in New Zealand, as firsthand knowledge is now available for its conduct. Machinery ’for the Domniion*

-Mr Thompson contracted for the supply of , a quantity of up-to-date machinery from Canada and the United States at a total cost of approximately £86,855. This is to be distribute! OV©r the Hauraki Plains, Rangitaiki jMwfos. Kaitaia, Waihi, Poukawa, and

Hikurangi swamp drainage works. Concerning the future, Mr Thomp son states that to date the drainage operations ..carried out under Government control have resulted in bringing swamp land to a profitable use and expectations have been more than realised. The operations are incomplete as regards present undertakings, and there are many areas untouched which it would, pay to take, in hand. There are many purely swamp areas throughout the Dominion, small individually, but large in the aggregate, which must in the ordinary course be reclaimed. The periodically 'Qooded bottom lands in the flood-plane slopes of rivers is another avenue of development. Fortunately gravity drainage governs the larger proportion of future possible reclamation projects. There will come a time when necessity will demand .intensive cultivation of swamp and marsh areas, holdings will become smaller, and the necessity for close drainage will arise. To meet these conditions tile drains will he required in sizes of 6in and upwards. Their use has been most successful, and they will eventually largely replace open ditches which require so much land.