Showing papers by "Ministry of Public Works published in 1996"

An analysis of land use/cover change in Indonesia

Abstract: The phenomena of land use/ change were evaluated by using a remote sensing approach in a case study in Yogyakarta, Indonesia. The index of changes, which was calculated by the superimposition of land use/ images of 1972, 1984, and land use maps of 1990, were introduced to analyse the pattern of change in the area. The results demonstrated that the pattern of land use/ change in the study area was that of paddy coverage to open/ land to settlement. The annual growth ratios of new settlements to absorb paddy coverage, mixed vegetation, and open/ land were 16 per cent, 20 per cent, and 64 per cent respectively. The larger the percentage of the paddy coverage, the higher the tendency for settlement growth to absorb the paddy coverage, and the larger the percentage of open/ land, the higher the tendency for settlement growth to absorb open/ land. Settlement growth had a high correlation with road accessibility. The highest settlement growth was distributed mostly in suburban areas between 200 and 400 ...

Sediment discharge by storm runoff from a creek on Merapi volcano

Abstract: Observation of storm runoff, suspended sediment and debris flow, and topographical surveys of the channel at the Bebeng River on the southwestern slope of Merapi volcano for 3 years since 1991, have clarified the characteristics of the low runoff coefficient for storm runoff, the large flux of suspended load, and the conditions of debris-flow occurrence, motion and deposition. Estimated annual sediment discharge through the observation site consists of 167,000 m3 of debris flows and 47,000 m3 of total load. Comparison of sediment transportation at three volcanic torrents on Mount Yakedake, Mount Unzen in Japan and Mount Merapi indicates a trend where the frequency and scale of debris flows, and the amount of sediment yield at a specific volcanic torrent generally decreases exponentially with the time after the last effective eruption. For example, annual depth of sediment yield or sediment discharge might be expected to decrease from the initial rate of 101-102 mm/year following the eruption to 101 mm/year in less than several years, and finally approach 10mm/year in less than a few decades.

Water balance on south-west slope of Volcano Mt. Merapi

Abstract: The Water balance on the south-west slope of Mt. Merapi in 1993 is made clear in this paper. The catchment in question is composed of four main rivers and several other small streams. The reason why so many rivers and streams were bundled together for analysis of the water balance can be found in the fact that all the rivers or streams have quite distinct runoff and it is difficult to ascertain the domain of the phreatic basin. Precipitation, evapotranspiration and runoff into and from the total subject catchment and each sub-catchment were estimated independently with data by direct measurement or by appropriate calculation. According to the calculation on the water balance, deep seepage disappearing out of the total subject catchment was as much as 1, 094mm. This value implies the existence of a huge amount of groundwater. The delivery of groundwater among sub-catchments is discussed for each of water balance, spatial distribution and characteristics of fluctuation of groundwater tables and the topography of sub-catchments. Consequently, the hydrological uniqueness of each sub-catchment and the complicated feature of groundwater in the volcano become clear.

Coastal management: Global change .... global observation?

Abstract: The theme of the present discussion is to consider coastal observation needs in the broader context of a sustainable, integrated management response to coastal change. Thus underlining the notion that observations are an element of a more comprehensive process. We will therefore first explore the process of ICZM, and find that deficits in international co-ordination and concertation are large. An overview of salient coastal zone issues emphasises the spatial, spectral and temporal diversity of observational needs, which is concluded to be an important reason for the relative underdevelopment of coastal zone observation systems. A "global" coastal observation effort should give due consideration to these aspects, and aim to help resolve this in concertation with national and international institutions carrying responsibility for a sustainable development of the coastal zone. The interpretation of the meaning of global appears to be twofold, global in the sense of a generic, universal need (although many coastal problems are local), and global in the sense of institutionalisation and co-ordination on a global level.

Aeration Versus Cavitation in Dam Spillways: Self-Aeration and Artificial Aeration (Aerators)

Abstract: This paper describes the most important aspects of the effect that flow aeration has in combating the damage caused by cavitation. An explanation is also given of how to characterise these flows when the air enters the flow in a natural way, as well as giving an account of some of the artificial aeration devices that are placed on spillways when natural aeration proves to be insufficient.