Leon Bren

Riparian zone, stream, and floodplain issues: a review

Abstract In the last two decades, the effects of forest management on streams, riparian zones, and floodplains have become of much interest. In general, there is agreement that such areas should be maintained in a state approximating naturalness, although it is recognised that definition of this state is usually difficult or impossible. A diversity of management effects has been recognised and, in some cases quantified. For upland catchments, issues particularly relate to direct disturbance of the zone, changes in the flow of woody debris into the stream, or disturbance to the environment by effects generated upstream or downstream. For many areas, a particularly important commercial aspect is the definition of a ‘stream’, as this can impose many expensive and severe restrictions on management of the land. For large rivers, a common issue is the effect of river management on flooding forests. In each case, the issues are complex, information is difficult to collect, and there are fundamental difficulties in going from anecdotal observation to data. Currently, most information appears to be at a relatively local level, and there is a very inadequate knowledge base to give a more holistic overview, although the concept of ‘cumulative effects’, with the effects accumulated over both space and time, has much potential value. There are many opportunities for work in this field.

Aspects of the geometry of riparian buffer strips and its significance to forestry operations

Abstract A stream buffer strip is an area within a defined distance from a stream in which land use activities are restricted for stream protection purposes. This study used a sophisticated Geographic Information System to examine the extent, distribution, and boundary properties of land defined by buffer strips of differing widths. The prototype catchment studied was the mountainous 65 km 2 Tarago River catchment in eastern Victoria. The West Tarago River is a fourth-order stream network. This was accurately delineated using the topographic map supplemented by high quality aerial colour transparencies. This showed that the map had inadequate detail of smaller streams. The streams had a branching network with an overall fractal dimension (measure of complexity) of 1.75, although the fractal dimension of the individual stream reaches was only slightly greater than one. The area of land occupied by buffers increased substantially with increasing width of buffers, with 95% of the catchment occupied by buffers of 300 m width. As buffer width increased to 100 m, many areas became entrapped by buffers and hence became effectively inaccessible. Individual boundaries reached their greatest complexity at 10 m buffer width, but the buffer/non-buffer network achieved greatest complexity at 100 m buffer width. Small buffers had a very high perimeter/area ratio. As buffer width increased the perimeter/area ratio of non-buffer areas slowly increased, reflecting that non-buffer areas were becoming smaller and more fragmented.

A case study in the use of threshold measures of hydrologic loading in the design of stream buffer strips

Abstract In forestry, a buffer area has logging excluded in order to protect stream values. In Victoria (Australia) the usual method is to define a stream and mark the boundary a set distance from the stream. However, this does not give any protection to watershed convergences that may not carry a definable stream, and it is easy to show major variations in the hydrologic loading of such areas. In contrast a buffer designed using measures of convergence can (in principle at least) give protection to such hollows and be independent of whether a ‘stream’ had been defined. These buffer limits would be set at a value consistent with the ‘natural threshold of erosion’. This paper explores the buffer properties given by two such measures–the specific area and the slope index. Both the parameters are closely related, but the slope index incorporates the local slope. It was found that the buffers given by a simple cut-off were not necessarily associated with streams, and that most protection was allocated to areas of watershed convergence (hollows) because these have high hydrologic loadings. In contrast, as one moved downstream the hydrologic loading tended to be so small that this method gave little or no buffering. Use of a ‘regional value’ on synthetic logging coupes showed a wide variation in the level of protection given in such areas. This reflects that many logging areas tend to be divergent and, in reality, have little need for buffer protection compared to their more convergent areas. The geometric pattern of buffers differed substantially from that associated with fixed buffer width protection, and shows that a major deficiency of the ‘fixed width’ approach is under-protection of source areas and overprotection of downstream slopes contributing to a waterway.

Harvester Productivity and Operator Fatigue: Working Extended Hours

Abstract Falling financial margins have prompted many owners of Australian harvesting businesses to extend normal working hours. After brief trial periods, most companies have again reverted to short-term and ad hoc solutions to meet peaks in demand. The harvesting industry is also being persuaded to operate extended hours under the guise of service-delivery and the ‘24-hour society’, in response to customer demand. A poor understanding of human factors poses a threat to profitable harvesting, and contributes to low productivity on extended hours work regimes. Decreased operator productivity was observed in both shifts of a shiftwork operation. Experience in other industries have noted reduced operator alertness led to increases in the risk and severity of accidents and machine damage. Successful implementation of extended hours work regimes relies on addressing operational needs as well as recognising the human needs, managing productivity, safety, communications and maintenance.

Remote sensing of post-fire vegetation recovery; a study using Landsat 5 TM imagery and NDVI in North-East Victoria

Development of effective management strategies for fire-prone landscapes is becoming increasingly important within South-East Australia. Monitoring of post-fire vegetation recovery is a critical process in developing these strategies, and is most effectively achieved using remote sensing techniques. This study analyses the effectiveness of Landsat 5 TM imagery and the Normalized Difference Vegetation Index (NDVI) in assessing regeneration rates of a mixed-species eucalypt forest in North-East Victoria, burnt on 6 December 2006. Multi-temporal analysis of regrowth data was performed, and standardised against an unburnt control area to eliminate any phenological factors affecting the region throughout the relevant timeframe. Results were compared with topoclimatic factors to reveal the level of stress affecting the study area both before the fire, and during post-fire regeneration.

An empirical, comparative model of changes in annual water yield associated with pine plantations in southern Australia

Summary Results from three Australian multiple catchment projects that examine the change in water yield on conversion from native eucalypt forest to radiata pine were combined. The projects were located in southern Australia near Myrtleford (Victoria), Daylesford (Victoria) and Bathurst (NSW). From these data a model of change in water yield relative to the eucalypt forest was derived using age and annual rainfall as independent variables. This model was extended to derive estimates of change in water yield from grassland sites converted to radiata pine by using the model of Zhang et al. (2001) to estimate the difference in water use between native forest and grassland. The results showed (and quantified) that conversion of native forest to radiata pine usually increases water yield but conversion of grassland sites to radiata pine usually decreases yields. Increased water yields are associated with young pines and high rainfalls, while decreased water yields are associated with older pines and low rainfalls. The models were tested using data from radiata pine plantations planted on grassland sites in Tumut (NSW), Kilmore (Victoria) and ‘fynbos’ in South Africa. In general the models performed reasonably well in estimating sequences of changes in flows. Estimates of total water yield were less accurate. Heavy or frequent thinning may be a source of change that may need to be accounted for separately if the details of this are known. The derived models may be useful in estimating the comparative changes of flow associated with the development of multiple blocks of radiata pine plantations on catchments. This can be programmed in a spreadsheet.

Hydrologic behaviour of a small forested catchment

Abstract The variations in discharge along a reach of stream emanating from a spring at the head of a small steep forested catchment in southeastern Australia were measured over a 4-yr. period. The results showed that the outflow of the springhead catchment was considerably less variable than the outflow of the catchment flanks along the length of the stream. Following substantial periods of rainfall the peak discharges from the springhead were reached some days after the cessation of rain, while the peak discharges from the flank catchment were reached during or immediately after the period of rainfall. Diurnal variations in summer streamflows were not observed at the springhead, but were observed with an increasing amplitude as distance downstream from the springhead increased. Field studies and mathematical analysis indicated that neither overland flow nor channel interception of rainfall were important in generating the streamflow response to any but very small storms, and that groundwater movement within a phreatic aquifer was the dominant process at all times. The hydraulic gradient of the groundwater was considerably steeper than generally attributed to such systems. To aid in interpretation, numerical solutions of the Boussinesq equation were used cast in a coordinate system approximating that of the component catchments. These showed that the observations are explainable as the effect of catchment shape on groundwater outflow. The computations indicated a noted perturbation in recession hydrographs may be attributable to the presence of a symmetry boundary associated with the ridge.

Forest Hydrology and Catchment Management

The water catchment is the fundamental concept underpinning quantitative hydrology. After considering equivalent terminology, the reader is introduced to analytical methods including flow vectors and catchment flow nets. The methods of defining catchments on a map, using a digital terrain model, or in the field are explained. The reader is introduced to streams (and catchments) of higher order and geomorphic rules which apply to the geometry of these in Australia. The arithmetic of catchment computations involving volume, area, and depth is explained, with particular consideration of the issue of avoiding confusion in units. Finally the reader is introduced to the stream hydrograph and the type of short-term and longterm variation encountered in these. Considerations of the differences between forest hydrology and the more general discipline of hydrology and how Australian hydrology differs from that of other parts of the world are made. As befits a book on forest hydrology, we have used three small forested catchments to illustrate many of the concepts described. These catchments – Clem Creek (46 ha), Ella Creek (113 ha), and Betsy Creek (44 ha) comprise the Cropper Creek Paired Catchment Project detailed in Sect. 5.2 of this book. Access to small streams and following their behavior is a great learning process; hence the use of data from these in this volume. 1.1 About Water Catchments and Stream Networks The most basic concept of hydrologic science is the catchment – the area of land contributing water to a nominated point on the earth’s surface. This is illustrated in Fig. 1.1 by a view of Clem Creek research catchment, in which the contributing area to the stream measurement weir is evident. This concept works well where there is a well-defined stream and ridge system. Equivalent terms are watersheds (US) and drainage basins (US & UK). The catchment can be further divided into spurs and ridges forming the boundaries (also occasionally called “watersheds”), the slopes which comprise the bulk of the land (often divided into upper and lower slopes), the stream, sometimes drainage lines (old stream beds which don’t usually carry water), and the riparian or gully zone in direct association with the stream.

On spatial variability of above-ground forest biomass

Abstract The topography-related variation and plot-to-plot variation of above-ground forest biomass in a central Appalachian watershed and in a southeast Australian watershed and its surroundings were compared. The Appalachian site was covered with typical Appalachian hardwoods, ca 85 years old, and the Australian site was covered with an eucalyptus forest ( Eucalyptus regnans ), ca 53 years old, when the study was initiated. Both forests are unmanaged. Biomass data were collected on 112 800 m 2 plots at the Appalachian site and on 30 plots of the same size at the Australian site. The oven-dry above-ground biomass average was 322 t/ha at the Appalachian site and 476 t/ha at the Australian site. At the Appalachian site, the single plot biomass varied from minus 67% to plus 85% of the mean, and at the Australian site the corresponding numbers are minus 50% and plus 61%. At both sites, the coefficient of variation shows a more or less steady value when the number of plots ( n ) exceeds 20. For n = 20, coefficients of variation are 28% and 22% for the Appalachian site and for the Australian site, respectively. The smallest above-ground biomass per unit area was observed on southwest-facing slopes at the Appalachian site and on west-facing slopes at the Australian site. The greatest above-ground biomass per unit area was observed on east-facing slopes at the Appalachian site and on south-facing slopes at the Australian site. In general, the sites facing east and the poles are more productive than those facing west and the equator.

The Basics of Catchment Hydrology

The water catchment is the fundamental concept underpinning quantitative hydrology. After considering equivalent terminology, the reader is introduced to analytical methods including flow vectors and catchment flow nets. The methods of defining catchments on a map, using a digital terrain model, or in the field are explained. The reader is introduced to streams (and catchments) of higher order and geomorphic rules which apply to the geometry of these in Australia. The arithmetic of catchment computations involving volume, area, and depth is explained, with particular consideration of the issue of avoiding confusion in units. Finally the reader is introduced to the stream hydrograph and the type of short-term and long-term variation encountered in these. Considerations of the differences between forest hydrology and the more general discipline of hydrology and how Australian hydrology differs from that of other parts of the world are made.