Remote sensing for resources development and environmental management: Remote sensing for resources development and environmental management

damen, m. c. j.

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Multivolume work

Persistent identifier:: 856342815

Title:: Remote sensing for resources development and environmental management

Sub title:: proceedings of the 7th international Symposium, Enschede, 25 - 29 August 1986

Year of publication:: 1986

Place of publication:: Rotterdam; Boston

Publisher of the original:: A. A. Balkema

Identifier (digital):: 856342815

Language:: English

Additional Notes:: Volume 1-3 erschienen von 1986-1988

Editor:: Damen, M. C. J.

Document type:: Multivolume work

Volume

Persistent identifier:: 856641294

Title:: Remote sensing for resources development and environmental management

Sub title:: proceedings of the 7th international Symposium, Enschede, 25 - 29 August 1986

Scope:: IX Seiten, Seiten 551-956

Year of publication:: 1986

Place of publication:: Rotterdam; Boston

Publisher of the original:: A,. A. Balkema

Identifier (digital):: 856641294

Illustration:: Illustrationen, Diagramme

Signature of the source:: ZS 312(26,7,2)

Language:: English

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Editor:: Damen, M. C. J.

Editor:: International Society for Photogrammetry and Remote Sensing, Commission of Photographic and Remote Sensing Data

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2016

Document type:: Volume

Collection:: Earth sciences

Chapter

Title:: 5 Non-renewable resources: Geology, geomorphology and engineering projects. Chairman: J. V. Taranik, Liaison: B. N. Koopmans

Write comment:: Wegen zu enger Bindung kommt es teilweise im Original zu Textverlust.

Document type:: Multivolume work

Structure type:: Chapter

Chapter

Title:: Monitoring geomorphological processes in desert marginal environments using multitemporal satellite imagery. A. C. Millington & A. R. Jones, N. Quarmby & J. R. G. Townshend

Document type:: Multivolume work

Structure type:: Chapter

risons between be more accurate s scene-to-scene xels correspond image. Six o-register the study with an ompared to twenty co-register the es. This confirms lity of the TM trol points ure were such as road will produce t images since surface cover ixels of the urious changes emove these r, with a 3 x 3 all the images detection and principle the most ms. Vegetation Singh, 1984) and unsuccessful ation changes in e to be detected in some margins, there egetation changes. MSS Band 7 nm) and 7 (2080- y subtracting the date from that nstant to ensure . Ratio images for the first or the principal eing compared e analysis, d 7 (800-1100nm) nds 4 (760-900nm), were used for to the use of ge detection to overall e contained in istically minor s in land cover (Byrne et al., on and Milne, nents 2 and 3 change in this previous , were applied s at +la from duced by nded to pixels f a colour and either the green gun in IANGE DETECTION playas. tudied using tions in this The Chotts el Djerid and el Fedjadj occur to the south of the Atlas Mountains in a zone of subsidence and they form part of a series of playas stretching from southern Tunisia to central Algeria . Chott el Djerid is the largest of these playas (5360km 2 ), it has an elongated north eastern arm, the Chott el Fedjadj, which continues eastwards into the Sebkhet el Hamma (770km 2 ). Their geomorphology and hydrology have been the subject of a number of investigations (Coque, 1962; Coque & Jauzien, 1967). Chott el Guettar (75km 2 in area) is situated in an enclosed basin about 20km SE of Gafsa. It is bounded to the north by the Djebel Orbata and the south by the Djebel Berba; both of these mountain ranges have active fans encroaching on the chott. Low ground and smaller mountains and hills are found to the east and west of the chott. 4.2. Geomorphological changes on playas Geomorphological changes have been detected on these playas from satellite imagery and ground survey, and they can be attributed to the seasonality of the hydrological regimes, surface salt concentrations, interactions with adjacent landforms and aeolian activity. These factors support the existance of seasonal patterns of climatically-controlled geomorphological change. Other geomorphological phenomena respond to fluctuations with either shorter or longer periodicities than the seasonal patterns and are not necessarily related to climatic fluctuations. If the temporal and spatial parameters of the geomorphological changes on playas are combined they can then be classified into 3 groups (Table 1). This subdivision is of fundamental importance because it recognises that specific types of change can be observed with different types of satellite data and different intervals between image acquisition as distinct from those that can only be observed by other techniques. Seasonal changes are readily detected by change detection algorithms applied to satellite imagery from the different seasons. Imagery corresponding to wet and dry conditions have been compared for all three playas in this study and four types of geomorphological changes in parameters affecting the geomorphology of the playas have been identified - 1. - surface moisture (standing water and subsurface moisture) 2. - surface texture and composition 3. - vegetation cover 4. - aeolian activity Seasonal patterns related to surface moisture and vegetation are best illustrated by examining change detection images between winter 1983 and summer 1985 TM imagery of the Chott el Guettar (Fig. 1). The greatest changes are those related to the fan delta at the end of the eastern fork of the Gafsa Fan and the adjacent chott. The fan delta is relatively well vegetated with Crassula spp, Limoniastium gyonianum and Limonium spp, and slopes very gently towards the chott without any obvious distal channel. Subdued sparsely vegetated topographic depressions act as surface water collecting areas which drain into rills, these feed into channels of about 2m depth and 50-100m width which drain into the chott. The individual channels and their restriction to the distal end of the fan delta can be clearly seen (Fig. 1) . The adjacent chott surface is moist throu^i- out the year and has a similar, but less dense, vegetation than fan delta. The change detection imagery (Fig. 1) indicates higher middle IR absorption on the fan in winter than summer. This can be explained by a combination of higher levels of soil and foliar moisture. The channels and adjacent chott areas are characterised by higher reflectance in the summer than the winter . The high summer middle IR absorption is related to higher soil moisture levels found in these areas, a response to the relatively high groundwater seepage through the Gafsa Fan due to irrigated agriculture. The higher winter reflectance values appear paradoxical considering the increased surface flow but are probably related to the fact that as flow is intermittent, water evaporates between flow events leaving surface salt effloresences. Combined field and satellite data suggests that surface water gathers on the fan delta and flows into the eastern part of the chott in winter and that in the summer the area is dominated by high levels of groundwater seepage. The area influenced by winter surface water and high summer moisture forms a roughly semi circular area adjacent to the fan with a lobe to the south. Similar patterns in winter surface water contributions have been seen on MSS change detection imagery. The other areas contributing surface water appear to be far less important. Increased winter surface or subsurface flow along the Oued el Rahr and Oued es Sedd systems to the east and northeast of the chott respectively is visible (Fig. 1). However, the chott area affected by water from the east is far less extensive than the west and according to the imagery is more variable in extent. Water flowing onto, or seeping through, the alluvial fans to the north shows little seasonal variation on the imagery. This is probably due to a lack of surface flow in the years examined, the dominance of a relatively constant groundwater seepage or the 'filtering' effect of the El Guettar oasis. Most of the fans to the south of the chott also show a similar effect despite the lack of a similar vegetation 'filter'. However substantial changes in moisture levels in the south-east chott were seen on 1981 change detection imagery (Fig. 2) which can clearly be linked to surface water flow in fan- channels . As there is little evidence of any kind of aeolian activity groundwater seepage and surface water control the transport of salts and sediments onto chott and their redistribution within the chott. The main seasonal changes in surface water and near-surface moisture are related to winter runoff from the eastern fan delta, and to a lesser, extent the channels draining Guettaria. A less frequent source of surface water is from the southern alluvial fans. Surface runoff acts as the main transport mechanism for sediment movement into the chott. This is particularly important in the areas adjacent to the southern fans. In addition there is an area of active gullying on fine-grained old chott sediments to the south-west of the chott. These gullys drain into the chott and act as a further sediment source area. They can be distinguished on the imagery as a cluster of small patches of high winter middle IR reflectance (Fig. 1). The sediment moving into the chott from the south forms a south-central depositional wedge which is recognisable in all change detection images as an area of lower summer Band 7 reflectance (Figs. 1 & 2). This is due to the increased water holding capacity of the sediments resulting in high soil and foliar moisture levels in winter. Salt transport, unlike sediment transport, is related to both surface water and groundwater fluxes and it is likely to mirror the hydrological regimes more strongly than the sedimentation patterns. Seasonal changes in surface texture and composition are most noticeable on imagery from the Chott el Djerid. These are particularly well developed in the north-central Chott el Djerid where the Fatnassa- Deajache road traverses it (Fig 3). Mitchell (1982) has divided the Chott el Djerid into 7 surface detail classes and 4 of these occur on the area of the chott traversed by the road:- 1. Wind sculpted, hummocky terrain 2. Thick salt crusts 3. Aioun (standing water and salt efflorescences) 4. Blistered thin crust with polygonal ridging

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