SOIL WATER

SOIL WATER INFILTRATION

Ted Floyd                                             Paper presented

Stormwater Industry Association,

4th Annual Conference, Sydney Sept. 1996

INTRODUCTION

It is well known that urban development increases flooding. In urban areas the coefficient of runoff increases, and the time of concentration decreases. The coefficient of runoff in undisturbed areas can be as low as 0.1, while in inner city suburbs, coefficient of runoff can be as high as 0.9.

Roads, roofs and paving are impervious with a coefficient or runoff approaching 1, while garden soils can be highly permeable with a coefficient of runoff approaching 0 during low intensity rainfall.

Flood control in urban areas traditionally involved the construction of pipes and channels designed to drain water away as quickly as possible. Several problems have been encountered with this approach.

Recent methods of flood control utilise many technologies to store water during rainfall, then to slowly release the water.

This paper aims to present some ideas on the capacity of soils to act as a reservoir of water. Methods to increase water infiltration into soils will be reviewed. Emphasis will be placed on soils in parks and gardens. Special devices such as rubble drains will only be briefly mentioned.

The author strongly believes catchment management should begin as high up in the catchment as possible. The principle of Upper Catchment Management should be followed in all Total Catchment Management schemes.

Improving the water absorption capacity of soils is the first step in Upper Catchment Management. The author does not claim the improvement of soils will solve all flooding problems, though soils should be considered in all Total Catchment Management plans. It should be recognized, a flood is a flood, and a good question would be, how big a detention basin would have been required to save Noah’s compatriots.

see full article « SOIL WATER

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WATER MANAGEMENT IN PARKS AND GARDENS

By Ted Floyd

Prepared for  Friends of the Earth

1998

Summary

The management of urban runoff is an important issue in all cities. The traditional management approach is to construct stormwater drainage systems with concrete pipes, channels and gutters. This heavy engineering approach is now not accepted by many urban designers.

The role of soils and plants in the water cycle is described in this report. Water management, taking advantage of the useful properties of plants and soils can be a useful tool for reducing stormwater problems in urban areas.

Several park management features are proposed in this report including: sunken gardens, wetlands and contour layout. Soil management can help to improve water infiltration into soils. These management features can reduce flood peaks and water pollution.

Public expectations are changing. In the past flooding was the primary concerne, but now pollution and provision of habitat are considered to be important issues.

Many stormwater problems can be reduced by mimicking nature. The natural water cycle should be studied and relevant information gained from nature incorporated into stormwater management schemes. Soil management can help to improve water infiltration into soils, reduce surface runoff and decrease flooding.

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