Master thesis topics Masterproefonderwerpen · 1 To: students 1ma Geography, 1ma Physical Land...

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To: students 1ma Geography, 1ma Physical Land Resources

Master thesis topics

Masterproefonderwerpen

Prof. Dr. Jan Nyssen

(2017-2018)

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1. Topographic rain zones and regional rain shadows related to

mountain massifs in the Ethiopian highlands

Promoter: Prof. Jan Nyssen

Co-Promoter: Prof. Piet Termonia

Advisors: Dr. Miro Jacob and Etefa Guyassa (UGent Department of Geography)

Note: Fieldwork in Ethiopia is optional for this master thesis.

In mountainous countries mapping of annual rainfall depth often done using interpolations that

involve longitude, latitude and possibly elevation of meteorological stations. Such an approach

does not allow to account for dominant wind directions and rain shadow.

For instance, in Ethiopia, slope aspect has been demonstrated to be an important explanatory

factor of rainfall depth (Nyssen et al., 2005).

On rainfall maps at different scales, the major massifs appear to induce topographic rain on the

windward side, and rain shadow on the leeward side. For instance it has been demonstrated that

the Semien mountains (4560 m) throw a rain shadow on its northern slopes (Puff & Nemomissa,

2001, Fig. 3B) that is believed to extend hundreds of km further to the NNW (Feoli et al., 2002;

Deyassa et al. 2014).

Also at local scale relatively minor massifs generate a similar effect. The Dogu’a Tembien

massif (photo), under conditions of dominant southwesterlies in the rainy season, generates a

topographic rain zone near Abi Adi and Hagere Selam, and less rain (including frequent

catastrophic droughts) in the Wukro-Senkata area.

The Dogu’a Tembien massif, seen from the West. Difference in elevation between the lowlands

in front and the crestlines is 1200-1400 m.

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Topography (left) and annual rainfall (right) in Geba catchment. Wind direction during the

rainy season is from the SW. The high rainfall around Abi Adi is thought to be largely of

orographic nature, induced by the Dogu’a Tembien massif around Hagere Selam. A rain

shadow occurs then in the Senkata-Wukro area (Etefa et al., 2016). Dots are monitoring sites

for land cover since the 1930s.

Using station data and the state-of-the-art ALADIN climate model, as well as the expertise

available at the RMI, the student will study the annual rainfall distribution in northern

Ethiopia in relation to global circulation, orographic forcing, and föhn effects. Inputs will also

be provided through an ongoing MSc research on “Rainfall and drought modelling in Ethiopia

using the ALADIN model” (Sander Van Vooren, Dept. Geography, UGent).

References

Deyassa, G., Kebede, S., Ayenew, T. and Kidane, T., 2014. Crystalline basement aquifers of Ethiopia: Their

genesis, classification and aquifer properties. Journal of African Earth Sciences, 100, pp.191-202.

Etefa Guyassa, Frankl, A., Amanuel Zenebe, Lanckriet, S., Biadgilgn Demissie, Gebreyohanis Zenebe, Poesen,

J., Nyssen, J., 2016. Changes in Land Use and Cover over 80 Years in the Highlands of Northern Ethiopia. In

preparation.

Feoli, E., Vuerich, L.G. and Zerihun, W., 2002. Evaluation of environmental degradation in northern Ethiopia

using GIS to integrate vegetation, geomorphological, erosion and socio-economic factors. Agriculture,

Ecosystems & Environment, 91(1), pp.313-325.

Nyssen, J., Vandenreyken, H., Poesen, J., Moeyersons, J., Deckers, J., Mitiku Haile, Salles, C., Govers, G., 2005.

Rainfall erosivity and variability in the Northern Ethiopian Highlands. Journal of Hydrology, 311: 172-187.

Puff, C. and Nemomissa, S., 2001. The Simen Mountains (Ethiopia): comments on plant biodiversity, endemism,

phytogeographical affinities and historical aspects. Systematics and Geography of Plants, pp. 975-991.

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2. Environmental impacts of export crops: mapping the effects of khat

(Catha edulis) and cut flower production on the water balance in

Ethiopia


Co-Promoter: Dr. Enyew Adgo, Bahir Dar University, Ethiopia

Local advisor: Etefa Guyassa (UGent Department of Geography, and Mekelle University,

Ethiopia)

Note: Fieldwork in Ethiopia is optional for this master thesis.

Khat (Catha edulis) is a mild narcotic that is widely produced in Ethiopia for export to

countries along the Red Sea and the Gulf of Aden and for local consumption (at high social

cost – Teni et al., 2015). It is a permanent crop (bush or small tree), the water consumption of

which has been studied (Al-Hebshi & Skaug, 2005; Gebere et al., 2016), but its spatial

distribution has never been mapped. Cut flowers, grown under plastic greenhouses, are also a

major export product of Ethiopia, and have been blamed for negatively impacting the

country’s water resources (Sahle & Potting, 2013; Breu et al., 2016). Yet, it remains to be

analysed whether this perception is correct or if the irrigated narcotic is not a much higher

water consumer. Mapping spatial distribution of both irrigated export crops, will also

contribute to policy decisions concerning such crops.

Khat plantation near Dire Dawa, Ethiopia (Photo: Simon Roughneen)

The student will (i) map khat areas and flower greenhouses from Landsat imagery, using

GCPs provided by the promoters; (ii) do a literature review on water consumption by both

crops; (iii) map water abstraction by both crops; and (iv) calculate the share that is abstracted

from Ethiopia’s major rivers by production of these crops in their basins.

The study can be done through desktop analysis. Additional fieldwork in Ethiopia is also

possible (GCP recording for both crops; irrigation application rates). See practical fieldwork

information, as presented with the other MSc topics for Ethiopia.

References:

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Al-Hebshi N, Skaug N. 2005. Khat (Catha edulis) – an updated review. Addiction Biology 10: 299–307.

Breu, T., Bader, C., Messerli, P., Heinimann, A., Rist, S. and Eckert, S., 2016. Large-Scale Land Acquisition and

Its Effects on the Water Balance in Investor and Host Countries. PloS one, 11(3), p.e0150901.

Gebere, S.B., Alamirew, T., Merkel, B.J. and Melesse, A.M., 2016. Land Use and Land Cover Change Impact

on Groundwater Recharge: The Case of Lake Haramaya Watershed, Ethiopia. In Landscape Dynamics, Soils and

Hydrological Processes in Varied Climates (pp. 93-110). Springer International Publishing.

Lemessa, D., 2001. Khat (Catha edulis): botany, distribution, cultivation, usage and economics in Ethiopia.

Addis Ababa: UN-Emergencies Unit for Ethiopia.

Sahle, A. and Potting, J., 2013. Environmental life cycle assessment of Ethiopian rose cultivation. Science of the

total environment, 443, pp.163-172.

Sahle, A. and Potting, J., 2013. Environmental life cycle assessment of Ethiopian rose cultivation. Science of the

total environment, 443, pp.163-172. Teni, F.S., Surur, A.S., Hailemariam, A., Aye, A., Mitiku, G., Gurmu, A.E.

and Tessema, B., 2015. Prevalence, Reasons, and Perceived Effects of Khat Chewing Among Students of a

College in Gondar Town, Northwestern Ethiopia: A Cross‑sectional Study. Annals of medical and health

sciences research, 5(6), pp.454-460.

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3. A 3D representation of the late Tertiary clay-with-flint peneplains of

E Belgium and N France/SE England: what does it learn us about

neotectonics and current valley asymetries?

Driedimensionele voorstelling van schiervlaktes op vuursteeneluvium in

Oost-België, Noord-Frankrijk en Zuidoost Engeland; wat leert het ons

over neotektoniek en asymetrische valleien?


Het voorkomen van vuursteeneluvium is een getuige van schiervlaktes die ontstonden tijdens

het Tertiair op kalksteenafzettingen uit het Krijt. Ze komen voor in het Oosten van het land,

maar ook in Noord Frankrijk en Zuidoost Engeland. Bij Valkenburg (NL) komt het

vuursteeneluvium voor op een hoogte van 150 m, maar een honderdtal km ten Zuiden, zijn er

resten van de formatie op de toppen van de Hoge Venen. De schiervlakte zit dus niet meer

horizontaal. Aan de hand van geologische kaarten, ondersteund door terreinobservaties zal de

student de afzettingen precies in kaart brengen, en daarna een driedimensionele voorstelling

van de vlaktes met hun huidige hellingsgradient uitwerken. Dit wordt dan verder gelinkt aan

de voorkomende neotektoniek van het Ardens massief. Ook zal de student onderzoeken of de

huidige helling van het schiervlak een band vertoont met het mogelijke voorkomen van

asymmetrische valleien.

Een voorbeeld:

http://www.hertsgeolsoc.ology.org.uk/IntroToHertsGeology.htm

Voor Zuid-Nederland en Oost-België, zie zeker het werk van Felder en de vele referenties

erin, alsook een kaart van het voorkomen van vuursteeneluvium.

http://www.hertsgeolsoc.ology.org.uk/IntroToHertsGeology.htm

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4. Reconstruction of the geometry of the ferricrete (Diestiaan

ijzerzandsteen) palaeosurface; evidence for a sudden regression

related to the Zanclean Event?

Reconstructie van de geometrie van het schiervlak op de Diestiaan

ijzerzandsteen; aanwijzingen voor een plotse regressie in verband met

de Zancleaanse vloed?


De student zal de theorieën van Gullentops (1957) en Vandenberghe et al. (2014)

confronteren met de realiteit van het hypervlak doorheen de Diestiaan ijzerzandsteen

afzettingen.

Gullentops: “Na het Diestiaan: Zanclean flood snelle daling van niveau van oceanen

zandbanken ontbloot precipitatie van Fe onder tropische omstandigheden”

Vandenberghe et al., 2014: “Valleibodems waarin ferricrete precipitatie plaatsvond, en daarna

erosie en reliëfinversie”

Aan de hand van geologische kaarten, ondersteund door terreinobservaties zal de student de

Diestiaan ijzerzandsteen afzettingen precies in kaart brengen, en daarna een driedimensionele

voorstelling van de afzetting met hun huidige hoogteligging uitwerken.

Als dit een horizontaal vlak is of was tijdens de periode van de Zancleaanse vloed, is dat een

argument dat de theorieën van Gullentops kan bevestigen. Als de geometrie van de

afzettingen eerder overeenkomt met een dendrietisch rivierpatroon, pleit dat voor

Vandenberghe et al.

Voor een samenvatting van de theorieën van Gullentops en Vandenberghe et al., zie Dusar,

M., 2015. Geowaarden van de Wijngaardberg. Natuur en Landschap, 2015: 4-7.

Voor de Zancleaanse vloed, zie o.a. Garcia-Castellanos & Villaseñor, 2011.

Voor Ferricretes en reliëfinversie, zie o.a. Ollier & Seth, 2008.

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5. Scientific communication on soil erosion control to smallholder

farmers in developing countries: a meta-study of pathways (oral,

written, media), approaches and actors involved


Advisor: Hailemariam Meaza (UGent Department of Geography, and Mekelle University,

Ethiopia)

Extension, or distribution of scientific knowledge to the farmers in Africa and Ethiopia in

particular, goes through a long formal and structured extension system.

However, over the centuries farmers have shared their knowledge what allowed the spreading

of innovations. For instance, the miguemas or shilshalo technique for sorghum leads to

strongly improved yields and was developed many centuries ago, and spread all over the Horn

of Africa and Yemen (Nyssen et al., 2011). Throughout Ethiopia, when farmers grow

sorghum or maize, they use the marasha or ard plough to create contour furrows within the

standing crop during the (second) weeding operation (Gebreyesus Brhane et al., 2006). The

technique has been documented also in Yemen (Bédoucha, 1986; Varisco, 2004). Besides

weeding and plant thinning, the aim of the practice (miguemas in Tigrinya, shilshalo in

Amharic and south Tigray; Table 1) is to enhance runoff capture, particularly in semi-arid

areas. In our target area, and despite the existence of very heavy rains in August when

shilshalo is practiced (Nyssen et al., 2005), the furrows are made along the contour and are

slightly curved upwards at both ends of the farmland to enhance the water harvesting effect.

In addition, plant physiologists pointed to the sorghum crop root pruning that takes place and

which enhances root growth (Blum, 2004; Blum et al., 1977; Rajaram et al., 1991).

Shilshalo ploughing as practiced on sorghum, some weeks after emergence in the May Zegzeg catchment. In one

tillage operation, weeding, thinning and root pruning is done; the furrows also decrease runoff and enhance

infiltration.

In Ethiopia, the structural extension system also allowed many advances such as soil and

water conservation or improved seed varieties, or milk production. But in the same time it is

carried out in a top-down approach, imposing sometimes priorities that are not necessarily the

farmer’s priorities, such as fertiliser use when soils are fertile, or when rainfall is uncertain, or

biofuel plantations without market.

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Jatropha was introduced as a biofuel plant through the extension system in Tigray, Ethiopia. The plants grow

vigourously, produce high yields, but there is no factory to process it and no market for it.

Extensionists or Development Agents also try to force results (in order to increase their own

chance for promotion) by bartering a package against benefits for the farmers such as work

opportunity or food aid (see Segers et al., 2008). Farmers’ days are organised but to what

extent do they address only model farmers, and does the information really trickle down to

society?

A farmers’ day typically consists of a joint visit of places were innovations were successfully implemented

Recently, theories have been developed that give much more focus to farmer-to-farmer

extension. How and to what extent are such methods really implemented in the field, and what

is then the (reduced) role of the scientist and the extensionist? Is farmer-to-farmer only

working through oral communication, or is there the necessity of a written support? Could the

17th-20th centuries’ almanacs in Europe stand as an example for written support of agricultural

extension (Bollème, 1975; Gaspard, 1986)?

This requires a detailed and thorough literature study contrasting theories and cases, both for

ancient and recent spread of innovations in agriculture and land management.

References

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Bédoucha, G., 1986. Une antique tradition chez les hommes de tribu des hauts plateaux yémenites: la culture du

sorgho. Techniques et Culture, 8, 1-68.

Blum, A., 2004. Sorghum physiology. In: H.T. Nguyen, A. Blum (Eds.), Physiology and Biotechnology

Integration for Plant Breeding. CRC Press, Boca Raton, FL, USA, pp. 141-224.

Blum, A., Arkin, G.F., Jordan, W.R., 1977. Sorghum root morphogenesis and growth. I. Effect of maturity

genes. Crop Science, 17, 149-153.

Bollème, G., 1975. La Bible bleue: anthologie d'une littérature populaire. Paris, Flammarion.

Gaspard, C., 1986. Les almanachs de l'an II: Quoi de neuf en dehors du calendrier? Annales historiques de la

Révolution française. Société des Etudes Robespierristes: 141-159.

Gebreyesus Brhane, Wortmann, C.S., Martha Mamo, Heluf Gebrekidan, Amare Belay, 2006. Micro-Basin

Tillage for Grain Sorghum Production in Semiarid Areas of Northern Ethiopia. Agron J, 98(1), 124-128.

Nyssen, J., Vandenreyken, H., Poesen, J., Moeyersons, J., Deckers, J., Mitiku Haile, Salles, C., Govers, G., 2005.

Rainfall erosivity and variability in the Northern Ethiopian Highlands. Journal of Hydrology, 311(1-4), 172-187.

Nyssen, J., Govaerts, B., Tesfay Araya, Cornelis, W.M., Bauer, H., Mitiku Haile, Sayre, K., Deckers, J., 2011.

The use of the marasha ard plough for conservation agriculture in Northern Ethiopia. Agronomy for Sustainable

Development, 31 (2): 287-297.

Rajaram, G., Erbach, D.C., Warren, D.M., 1991. The role of indigenous tillage systems in sustainable food

production. Agriculture and Human Values, 8, 149-155.

Segers, K., Dessein, J., Nyssen, J., Mitiku Haile, Deckers, J., 2008. Developers and farmers intertwining

interventions: the case of rainwater harvesting and food-for-work in Degua Temben, Tigray, Ethiopia.

International Journal of Agricultural Sustainability, 6(3): 173–182.

Varisco, D.M., 2004. Terminology for plough cultivation in Yemeni Arabic. Journal of Semitic Studies, 49, 71-

129.

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6. Quantification of the water balance and scenarios for water use at

historical water mills – case of the Van den Borresmolen in Strijpen

(Belgium)

Begroting van de waterbalans en scenario’s voor waterbeheer bij

historische watermolens – de Van den Borresmolen te Strijpen (België)


Advisor: Ir. Simon De Boever

Historische watermolens berusten op top-technologie die dateert van het proto-industriële

tijdperk. Deze studie zal bijdragen tot het begrijpen van de hydrologische principes die gevolgd

werden om het waterverbruik te optimaliseren bij bovenslagmolens bij rivieren met een klein

en onregelmatig debiet.

De studie zal uitgevoerd worden bij de nog werkende Van den Borresmolen te Strijpen, “een

van de weinige ongeschonden watermolensites in Oost Vlaanderen.”

http://www.molenechos.org/molen.php?AdvSearch=494

De situatie rondom de molen: links (de Ferraris, 1771-1778); rechts in 2007 (NGI).

Schema van het hydrologisch systeem rond de Van den Borresmolen (verticale coupe, niet op

schaal). Dit zal gebruikt worden om de conceptuele hydrologische balans op te stellen.

Grafisme: Hanne Hendrickx.

http://www.molenechos.org/molen.php?AdvSearch=494

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Het onderzoek zal bestaan uit het opstellen van een conceptuele hydrologische balans voor

verschillende situaties (werkende molen, wateropslag, hoge debietsituatie), en het opmeten

van verschillende termen ervan (debieten, neerslag, wateropslag), en modelleren/afleiden van

andere (subsurface flow, evapotranspiratie).

Ook zal het effect van verschillende alternatieve scenario’s berekend worden: - Vergroten van de molenvijver (en dus vergroten van opslagcapaciteit)

- Aanleg van een vistrap (en bypass)

- Bijkomend gebruik van molenvijver als stormbekken (vermindering van opslagcapaciteit)

Het toegepaste nut is het verhogen van groene energieproductie door de watermolen.

Voor dit onderzoek is een goede samenwerking opgezet met de molenaar, Ir. Simon De

Boever.

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7. Regional geomorphology of the Keiwelbach catchment (GDL)

Promoter: Prof. Dr. Jan Nyssen

Co-promoters: Prof. Dr. Eric Cammeraat (UVA Amsterdam); Dr. Christophe Hissler (Centre

de Recherche Public - Gabriel Lippmann, Luxembourg)

Advisors: Ing. Jérôme Juilleret (Centre de Recherche Public - Gabriel Lippmann,

Luxembourg), Ing. Simone Marx (Ministère de l’Agriculture et de la Viticulture,

Luxembourg)

The Keiwelbach catchment (outlet at 49.84944°N, 6.232631°E) in Luxembourg’s Gutland is

one of the areas where geomorphological mapping may contribute to the understanding of

topography and hydrological response. The catchment is located on Keuper marl and mainly

under forest and cultivation land. The soil erosion and hydrological processes in the region

have been well studied (Fig. 1 and Fig. 2.)

Table I. (Imeson and Vis, 1984)

Figure 1. (Cammeraat, 2002)

The hydrological response of the two main subcatchments (Schroedeschhaff R. also called

Upper Keiwelsbach, and Mosergriecht) is known. High storm runoff coefficients in the

forested Upper Keiwelbach subcatchment (Fig. 1 and Table 1) are to be correlated to the

clayey nature of the soil under the forest (Imeson and Vis, 1984; Cammeraat 2002). The

question remains whether this is due to the impact of soil fauna on forest soils as stated by

Cammeraat & Kooijman (2009), or whether it is due to the intrinsic nature of the parent

material, as the soil map of the region tends to indicate (Fig. 3). In the latter case, it is

assumed that forests would have been maintained in this region because the fluctuating

perched water tables made the land not suitable for cropping.

In this and nearby regions, gullies occurring under forest have been related to the presence of

the high water table (Imeson & Vis, 1984); yet, the human impact must also be considered.

Anecdotal evidence tends to indicate that footpaths, drainage ditches and bridges may also

have enhanced runoff concentration. Sediment infill, evidencing a gully cut-and-fill cycle, can

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further be observed in a profile pit, pointing to land-use-related changes in geomorphic

processes and their rates.

Three profile pits have been opened in the catchment that will allow the student to do the

necessary profile descriptions and soil analyses (texture, relevant soil chemical parameters).

In order to provide answers to these research questions, the student will prepare a detailed

geomorphological map of the catchment (Degraaff et al., 1987; Gustavsson et al., 2006), in

line with the expertise of the physical geography research group (Annys et al., 2014; Frankl et

al., 2010; Poppe et al., 2013). Field observations and a wide set of relevant existing literature

will provide the necessary information. Soil types and landforms will be related to lithology,

topography and land cover through time.

As the research will be done in cooperation with our Luxembourg colleagues, the thesis will

have to contain an extended summary in English or French, or possibly be written in either of

these languages.

Fig. 2. (Duijsings, 1987)

Fig. 3. Part of GDL soil map (2010, prepared at 1:25 000). Dark shades: forest.

References Annys, K., Frankl, A., Spalević, V., Čurović, M., Borota, D., Nyssen, J., 2014. Geomorphology of the Durmitor

Mountains and surrounding plateau Jezerska Površ (Montenegro). Journal of Maps, 10(4): 600-611.

Cammeraat, E. 2002

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Cammeraat, E. 2006

Cammeraat E, Kooijman A. 2009. Biological control of pedological and hydro-geomorphological processes in a

deciduous forest ecosystem. Biologia 64(3), 428-432.

Degraaff, L. W. S., M. G. G. Dejong, J. Rupke and J. Verhofstad (1987). A Geomorphological Mapping System

at Scale 1:10,000 for Mountainous Areas. Zeitschrift Fur Geomorphologie 31(2): 229-242.

Duijsings J J H M. 1987. A sediment budget for a forested catchment in Luxembourg and its implications for

channel development. Earth Surface Processes and Landforms 12(2), 173-184.

Frankl, A., Nyssen, J., Calvet, M., Heyse, I., 2010. Use of Digital Elevation Models to understand and map

glacial landforms — The case of the Canigou Massif (Eastern Pyrenees, France). Geomorphology 115, 78–89.

Gustavsson, M., E. Kolstrup and A. C. Seijmonsbergen (2006). A new symbol-and-GIS based detailed

geomorphological mapping system: Renewal of a scientific discipline for understanding landscape development.

Geomorphology 77(1-2): 90-111.

Imeson A C, Vis M. 1984. The output of sediments and solutes from forested and cultivated clayey drainage

basins in Luxembourg. Earth Surface Processes and Landforms 9(6), 585-594.

Poppe, L., Frankl, A., Poesen, J., Teshager Admasu, Mekete Dessie, Enyew Adgo, Deckers, J., Nyssen, J., 2013.

Geomorphology of the Lake Tana basin, Ethiopia. Journal of Maps, 9(3): 431-437.

http://www.geoportal.lu/Portail/

A longer list of references of all earlier geomorphological research in the study area is available.

http://www.geoportal.lu/Portail/

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8. River channel response to land cover changes in the Ethiopian

Highlands since the 1930s

Promoter: Prof. dr. J. Nyssen

Co-promoters: Dr. Sil Lanckriet, Dr. Tesfaalem Gebreyohannes (Mekelle University)

Context

The dynamics of streams, and related flooding, are strongly governed by the characteristics of

discharge and sediment supply to their channels which in turn are controlled by the

geological, geomorphological, hydrological, climatic and vegetal characteristics of their

catchments [1-4]. In contrast to the geological and geomorphological factors, climatic

variability and land cover changes were shown to induce changes in stream channels over

short timescales in northern Ethiopia [5]. Eleven streams on the western Rift Valley

escarpment of Ethiopia have already been studied to understand how mountain streams have

reacted to land cover changes over the last eight decades. In the 1970s and 1980s, peak

discharge and the size of bed load supply increased. Consequently, stream channels increased

in width, straightened and braided. After reforestation starting from 1986, the channels have

narrowed, the braided pattern was abandoned in favour of a single thread, and boulder bars

and channels were stabilized by vegetation. Hence, it was demonstrated that reforestation of

steep mountain catchments can give quick response in reducing discharge and sediment

supply to the streams and thereby curb associated flooding calamities [5]. This study by

Tesfaalem Ghebreyohannes at Ghent University was the first to use the aerial photographs

(APs) of Ethiopia realised in the 1930s.

The Italian Military Geographical Institute has photographed large parts of Ethiopia in the

1930s, to prepare and sustain its war activities, and to establish infrastructure in that country

[9]. The nearly complete archive of this aerial photography was re-discovered by the

promoters in the Ethiopian Mapping Agency (EMA) building in Addis Ababa [9] and is at

hand.

The pre-eminent evidence of geomorphic activity in a mountainous landscape that can be

retrieved from APs is river morphology. Several researches have shown the strong

relationship between changes in vegetation cover of catchments and stream geomorphology.

Deforestation-induced increase in sediment supply causes channel widening, bank erosion and

increase in flood risk whereas reforestation is associated with reduction in runoff and

sediment supply and thereby narrowing channels, stabilization of bars, incision, changes from

braided to meandering patterns and new terrace levels [2, 4, 54-59]. In Ethiopia, such

phenomena have been described [10, 60] (Fig. 3) and studied in detail by the promoters in a

study area along the Rift Valley escarpment [5, 22, 38]. The MSc thesis student will study the

changes at a regional scale and in the long term, in contrast to earlier studies that were limited

in time or spatial extent.

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Fig. 1. Suluh River near May Tiwaru (13.7524°N, 39.5065°E), in 1936 (Italian aerial

photograph) and 2014 (Google Earth) [10]. The river channel has widened and gravel bars

appeared. Such changes will be quantified along several rivers draining the Ethiopian

highlands and correlated to land cover changes. Width of scene: approx. 650 m.

Fig. 2. Confluence of May Zegzeg river (at left) that drains a protected catchment [61, 62]

and Tsigaba river (at right) from a catchment with less vegetation cover. The sediment

deposits at the confluence (13.6141°N, 39.2263°E) can be clearly linked to the river that

drains the unprotected Tsigaba catchment. Image: Google Earth; width of scene: approx. 500

m.

1936

2014

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Study methodology

1. Selection of suitable rivers. River channels over the whole study area will be

systematically screened for the occurrence of gravel bars, both in the 1930s and

currently (Fig. 1; Fig. 2). To be done during the preliminary study, based on screening

of the already relocated APs.

2. Mapping changes to river channels. For selected subsets, the current spatial extent will

be measured in the field and on APs; similarly channel width will be measured at

regular intervals (100 m) using APs. In floodplains, the sinuosity will also be

measured for both periods. Temporal changes to these parameters will allow

characterising and mapping the changes to stream channel morphology.

3. Interpretation of landscape dynamics. Changes in channel characteristics will be

correlated to changes in land use and cover in the upper catchments.

4. Detailed case studies to be carried out for rivers with contrasted bed load (Fig. 2).

References

1. Schumm, S.A., River variability and complexity. 2005, New York: Cambridge University Press. 220.

2. Kondolf, G.M., H. Piegay, and N. Landon, Channel response to increased and decreased bedload supply from

land use change: contrasts between two catchments. Geomorphology, 2002. 45(1-2): p. 35-51.

3. Liébault, F., et al., Land-use change, sediment production and channel response in upland regions. River

Research and Applications, 2005. 21: p. 739-756.

4. Boix-Fayos, C., et al., Effects of check dams, reforestation and land-use changes on river channel morph-

ology: Case study of the Rogativa catchment (Murcia, Spain). Geomorphology, 2007. 91(1–2): p. 103-123.

5. Tesfaalem Gebreyohannes, Mountain stream dynamics as impacted by rainfall variability and land cover

change in the western Rift Valley escarpment of northern Ethiopia. PhD thesis. 2015, Ghent: Department of

Geography, Ghent University.

6. Nyssen, J., et al., The historical aerial photographs of Ethiopia in the 1930s Journal of Cultural Heritage, 2015:

online early view.

7. Everitt, B., Channel responses to declining flow on the Rio Grande between Ft. Quitman and Presidio, Texas.

Geomorphology, 1993. 6(3): p. 225-242.

8. Beguería, S., Validation and evaluation of predictive models in hazard assessment and risk management.

Natural Hazards, 2006. 37(3): p. 315-329.

9. Frankl, A., et al., Using image-based 3D modelling to produce a 1935 ortho-mosaic of the Ethiopian

Highlands. International Journal of the Digital Earth, 2015. 8(5): p. 421-430.

10. Billi, P., Semunesh Golla, and Dawit Tefferra, Ethiopian Rivers, in Landscapes and Landforms of Ethiopia,

P. Billi, Editor. 2015, Springer Netherlands. p. 89-116.

11. Tesfaalem Gebreyohannes, et al., Catchment rehabilitation and hydro-geomorphic characteristics of

mountain streams in the western Rift Valley escarpment of Northern Ethiopia. Land Degradation and

Development, 2015: p. online early view.

12. Tesfaalem Ghebreyohannes, et al., Adjustment of mountain stream channels to land cover variability - the

case of western Rift Valley escarpment of Ethiopia. Earth Surface Processes and Landforms, 2015: p. in press.

13. Nyssen, J., et al., How soil conservation affects the catchment sediment budget - a comprehensive study in

the north Ethiopian highlands. Earth Surface Processes and Landforms, 2009. 34: p. 1216-1233.

14. Nyssen, J., et al., Impact of soil and water conservation on catchment hydrological response – a case in

northern Ethiopia. Hydrological Processes, 2010. 24(13): p. 1880-1895.

FOR FIELDWORK

During the fieldwork, the MSc student will stay in small towns to the S and W of Mekelle; one

translator/field assistant will work permanently with him/her.

Some important points for students to consider before declaring an interest:

- The thesis will have to be written in English.

- Fieldwork period: 2 months between early July and late September 2017. This implies that

the student needs to make sure he/she will not have to take exams in August/September!

- Environment for the fieldwork: cool tropical climate (June/September is the rainy season),

keep in mind that you will work in the mountains; other culture, totally different food, other

norms for comfort; often no electricity; telecommunication is difficult; only a few busses per

19

day; the student will often move on foot (mountains; heavy rains possible in the afternoon). But

also: friendly, dynamic people and breathtaking landscapes, and a unique experience.

- Before departure, practical guidelines and information sessions will be provided

- Assistance by promoters during start-up; possibly other UGent Master students will be in the

region.

- Profile of the student: should be prepared to live and work with local farmers, technicians and

authorities; strong sense of autonomy and adaptability; conversational English.

- For European students, partial funding for the travel costs can possibly be obtained through a

“reisbeurs naar ontwikkelingslanden” (deadlines 12 December, or April-May), see

http://www.ugent.be/nl/onderzoek/financiering/ontwikkelingssamenwerking/beursmogelijkhe

denvlaamsestudenten/vlstudenten.htm#vlaamse-reisbeurzen

http://www.vliruos.be/media/6444173/student_oproep_reisbeurzen_2017_finaal.pdf

If you have practical queries about living and working in Ethiopia, you may want to get in touch

with students or researchers who recently did their thesis in Northern Ethiopia:

- Dr. Sil Lanckriet ([email protected])

- Dr. Amaury Frankl ([email protected])

- Hanne Hendrickx ([email protected])

- Sofie Annys ([email protected])

- Dr. Miro Jacob ([email protected])

Your local counterpart will be Dr. Tesfaalem Gebreyohannes [email protected]

http://www.ugent.be/nl/onderzoek/financiering/ontwikkelingssamenwerking/beursmogelijkhedenvlaamsestudenten/vlstudenten.htm#vlaamse-reisbeurzen



mailto:[email protected]






20

9. The impacts of flash floods of dryland rivers on agricultural systems in

the Raya graben (Ethiopia)

Promoter: Prof. dr. J. Nyssen

Co-promoter: Dr. Biadgilgn Demissie (Mekelle University)

Advisor: Hailemariam Meaza (UGent Department of Geography, and Mekelle University)

Introduction

Despite widespread problems of water scarcity, one of the main consequences of climate change

is an increase in global incidences of intense precipitation events, in return causing an increased

and intense flooding including in the arid and semi-arid regions of the world (Trenberth et al.,

2007; Kundzewicz and Kaczmarek, 2000). Arid and semiarid regions are particularly

vulnerable to this change in climate. Additionally, the highly nonlinear and flashy nature of the

runoff in these dry regions makes predictions of the impact on agricultural systems difficult.

Extreme rainfall events and the resulting floods usually could cause significant damage to

agriculture, ecology and infrastructure, disruption to human activities, injuries and loss of lives.

There is high recurrence of flood events in the marginal grabens of the Ethiopian Rift Valley

which are the main causes of agricultural failures and land loss, and life and housing loss.

Scientific information about the nature of flood risks on agricultural land and life are important

for proper planning of land use/cover in the study area. But less attention is given to the impacts

the flashy floods are inflicting in the farming systems and other land use/cover in the graben

floor. The purpose of this MSc thesis is therefore to assess and analyze the impacts that these

flashy floods are imposing on the agricultural activities, land use/cover and settlement in the

graben floor.

Objectives

The general objective of this MSc research is to investigate the impacts of the flash floods of

the braided rivers in Raya Graben on the farming activities, land use/cover and settlement. The

specific objectives are: (i) analyze the vegetation biomass change of the crops around the rivers,

(ii) analyze the land use/cover changes around the rivers, and (iii) quantify the changes in

biomass and land uses/covers and estimate the productivity

Methodology

The impacts of the flashy floods on agricultural production can be quantified and mapped using

satellite images and aerial photos. The Landsat imageries and/or MODIS NDVI will be used to

see the changes in biomass and estimate the productivity of the farmlands along/around the

braided rivers. High and/or medium resolution imageries will be used to detect the changes in

land use/cover abound the braided rivers. The remote sensing methods can be supported with

interviews, focus group discussions with the peasants and terrestrial photographs for qualitative

analysis and ground truthing. As per the need some documents related to production in the study

area will also be collected from the agricultural offices in the study area. For data organization

and analysis, GIS and RS software can be used (such as ArcGIS10, ERDAS Imagine 9.1,

IDRISI Selva, ILWIS and ENVI).

Expected output

The outputs of the MSc research will be quantified results and maps of the changes in the

productivity of the farmlands. This will give insight into how the flashy dry land rivers are

imposing impacts on the productivity of the farming systems in the graben floor.

21

Figure 1: Images of the study area showing how the rivers are braided (upper) and their impacts on farmlands and

other land uses/covers (lower).

References and recommended readings

Congalton, R.G.. Green, K. 2008. Assessing the Accuracy of Remotely Sensed Data. Principles and Practices,

Second Edition, CRC Press: Boca Raton, FL

de Mûelenaere, S., Frankl, A., Mitiku Haile, Poesen, J., Deckers, J., Munro, N., Veraverbeke, S. and Nyssen, J.

2014. Historical landscape photographs for calibration of Landsat land use.cover in the Northern

Ethiopian Highlands. Land Degrad. Develop. 25: 319–335.

Tian Gao, Bin Xu, Xiuchun Yang, Yunxiang Jin, Hailong Ma, Jinya Li & Haida Yu. 2013. Using MODIS time

series data to estimate aboveground biomass and its spatio-temporal variation in Inner Mongolia’s

grassland between 2001 and 2011. International Journal of Remote Sensing 34 (21): 7796-7810

Kundzewicz, Z. W., and Z. Kaczmarek. 2000. Coping with hydrological extremes. Water International 25(1):66–

75.

Branching out

River

Farmland

s

22

Thomlinson JR, Bolstad PV, Cohen WB. 1999. Coordinating methodologies for scaling land cover classifications

from site-specific to global: steps toward validating global map products. Remote Sensing of Environment

70: 16–28.

Trenberth K.E. and Dai A. (2007) Effects of Mount Pinatubo volcanic eruption on the hydrological cycle as an

analog of geoengineering. Geophysical Research Letters, 34, L15702, DOI:10.1029/2007GL030524.

FOR FIELDWORK

During the fieldwork, the MSc student will stay in Alamata, Mehoni and/or Kobo towns or

villages around them; one translator/field assistant will work permanently with him/her.


- The thesis will have to contain an extended summary in English or possibly be written in

English.






day; the student will often move on foot (relatively level terrain, sometimes long distances;

heavy rains possible in the afternoon). But also: friendly, dynamic people and breathtaking

landscapes, and a unique experience.


- Biadgilgn Demissie will help you starting up; possibly other Belgian Master students will be

in the region.















Your local counterpart will be Dr. Biadgilgn Demissie ([email protected])









23

10. Land use changes since the 1930s in Tigray, Ethiopia, using a unique

set of aerial and terrestrial photographs

Promoters: Prof. Jan Nyssen, Dr. Amaury Frankl (UGent)

Local advisor: Etefa Guyassa (UGent, Vakgroep Geografie; Mekelle University, Ethiopia)

UGent’s department of Geography is in possession of a unique photographic dataset

concerning the northern part of Ethiopia, what will allow to do land use change studies.

FIG. 1. An example of a set of four photographs comprising – from left to right – high oblique; low oblique; near-

vertical; and low oblique exposures in a fan configuration covering an area east of Quiha in Northern Ethiopia.

Date: 1935-12-16; Photo number Mai Dolo 11-2-37; centre of the vertical photo at 13.46574°N, 39.59906°E. ©

EMA. Width of the conformably oriented fan configuration is 36 cm on hardboard tile and 6.24 km on the terrain.

Permanent farmland boundaries are clearly visible, as well as bushland that occupies structurally determined

scarps. Bright dots correspond to threshing floors. (Nyssen et al., 2016)

1. Aerial photographs

The aerial photographs (APs) acquired in the period of the Italian occupation of Ethiopia

(1935-1941) have recently been discovered, scanned and organised (REF phot rec).

In total, the archive comprises approximately 34,000 individual photographs, made up of

8281 discrete assemblages, each comprising four adjacent photographs. An individual group

or set of four photographs comprises a vertical (nadir-pointing) photograph, flanked by two

low-oblique photographs and a single high-oblique photograph, which is present alternatively

at left and right (Fig. 1). All four photographs had been exposed simultaneously in a fan

configuration in the cross-track direction (perpendicular to the flight line) to ensure the widest

possible angular coverage of the terrain. The vertical and oblique photographs of each

successive set of four photographs overlap on the previous set by approximately 60% in the

along-track direction, to ensure stereo-coverage of the terrain. The format size of each

individual photograph in the archive is 10 cm x 15 cm, though many oblique photographs

were slightly cropped on their borders to minimise the seam with the nadir-pointing

photographs. All the photographs in the archive have been transformed into digital form at the

EMA offices in Addis Ababa using a Plustek A3 scanner (Optic Pro A320) with a resolution

of 600 dpi (Nyssen et al., 2016). Moreover, the scanned photographs have been carefully

organised into a searchable inventory (Fig. 2).

Up-to-date technology needs to be used for restitution of the imagery, particularly

orthorectification. Especially the vertical and low oblique photographs in the sets are of prime

value for the construction of orthophotographs of Ethiopia in the early 20th Century.

24

Using image-based modelling software with Structure from Motion and MultiView Stereo

(SfM-MVS) procedures implemented, workflows for development of such ortho-mosaics

have been developed (Frankl et al., 2014), although the high oblique photographs appeared

unsuitable for sake of insufficient overlap. As the archive consists of both oblique and vertical

aerial photographs, covering areas of approx. 4 km², methods of image-based modelling can

be used for the ortho-rectification. An example of the 1936 ortho-mosaic can be accessed

here: http://geoweb.ugent.be/download/physical-geography/research/environment-

ethiopia/Suluh.kmz

More recent aerial photographs (1964, 1994), as well as highly detailed recent Google Maps

imagery are also at hand.

FIG. 2. Location of 1987 relocated aerial photographs of the late 1930s, on 48 different flight lines. Each dot

represents the centre of the vertical photograph within an assemblage of four photographs. The study area is located

in the Northern highlands, (Nyssen et al., 2016)

2. Terrestrial photographs

Observational studies of land cover in Ethiopia date to the 1960s at the earliest, the age of the

oldest available aerial photographs. The recent rediscovery of large sets of historical terrestrial

photographs (Nyssen et al., 2010) allows for this research to now extend back to in time. To

date, these historical photographs have been used to study certain time periods, based on

interpretation of land used changes observed on the photos (Nyssen et al., 2008, 2009, 2014).

This study intends to go a step further.

Particularly, a large set of repeated ground photographs, representing the Ethiopian

landscapes at the time of Italian occupation, are available (Fig. 3).

Methodology

The study will consist of a land use change study since the 1930s, in which the interpretation

of the historical aerial photographs will be enhanced by ground truthing using the terrestrial

photographs. A study area will be selected where there is a dense coverage of historical

terrestrial photographs. The study will comprise the following activities

- Ground truthing of ancient land uses, using terrestrial photographs, in line with

methods developed by Meire et al. (2013) and de Mûelenaere et al. (2014)

http://geoweb.ugent.be/download/physical-geography/research/environment-ethiopia/Suluh.kmz

http://geoweb.ugent.be/download/physical-geography/research/environment-ethiopia/Suluh.kmz

25

- Field observations and interviews allowing to understand and map drivers for the

changes - Preparation of orthomosaics based on the historical aerial photographs, following the

method of Frankl et al. (2014)

- LUC change interpretation, mapping and analysis

Fig. 3 Example of one of the many repeated photographs, with interpretation: The remnant Juniperus trees in the

late 1930s are evidence of a vegetation optimum. In the period thereafter, nearly all of the woody vegetation in

the undulating lands in the foreground was cleared and farmlands were established, including strip lynchets. On

the scree slopes at the foot of the escarpment, the tree cover was approximately the same in both years, and the

far mountains were reforested in the 1980s as mixed Juniperus-Eucalyptus forests. Although the entire area was

open-access in the 1930s, the land use system has since been reorganized with clearly demarcated crop and

forest lands. Archival photograph © G. Merla; 2009 photograph © J. Nyssen. (Nyssen et al., 2014)

References - de Mûelenaere, S., Frankl, A., Mitiku Haile, Poesen, J., Deckers, J., Munro, R.N., Veraverbeke, S.,

Nyssen, J., 2014. Historical landscape photographs for calibration of Landsat land use/cover in the

northern Ethiopian highlands. Land Degradation & Development, 25: 319–335. - Frankl, A., Seghers, V, Stal, C., De Maeyer, Ph., Petrie, G., Nyssen, J., 2014. Using image-based

modelling (SfM-MVS) to produce a 1935 ortho-mosaic of the Ethiopian Highlands. International

Journal of the Digital Earth, online early view. - Meire, E., Frankl, A., De Wulf, A., Mitiku Haile, Deckers, J., Nyssen, J., 2013. Land use and cover

dynamics in Africa since the nineteenth century: warped terrestrial photographs of North Ethiopia.

Regional Environmental Change, 13(3): 717-737. - Nyssen, J., Poesen, J., Descheemaeker, K., Nigussie Haregeweyn, Mitiku Haile, Moeyersons, J., Frankl,

A., Govers, G., Munro, R.N., Deckers, J., 2008. Effects of region-wide soil and water conservation in

semi-arid areas: the case of northern Ethiopia. Zeitschrift für Geomorphologie, 52: 291 - 315. - Nyssen, J., Mitiku Haile, Naudts, J., Munro, R.N., Poesen, J., Moeyersons, J., Frankl, A., Deckers, J.,

Pankhurst, R., 2009. Desertification? Northern Ethiopia re-photographed after 140 years. Science of the

Total Environment, 407: 2749 – 2755. - Nyssen, J., Frankl, A., Munro, R.N., Billi, P. Mitiku Haile, 2010. Digital photographic archives for

environmental and historical studies: an example from Ethiopia. Scottish Geographical Journal, 126 (3):

185-207. - Nyssen, J., Petrie, G., Sultan Mohamed, Gezahegne Gebremeskel, Frankl, A., Stal, C., Seghers, V.,

Debever, M., Demaeyer, Ph., Kiros Meles Hadgu, Billi, P., Mitiku Haile, 2016. Historical aerial

photographs of Ethiopia in the 1930s and their fusion with current remotely sensed imagery for

retrospective geographical analysis. Journal of Cultural Heritage, 17: 170-178.

1936

2009

26

- Nyssen, J., Frankl, A., Mitiku Haile, Hurni, H., Descheemaeker, K., Crummey, D., Ritler, A., Portner,

B., Nievergelt, B., Moeyersons, J., Munro, R.N., Deckers, J., Billi, P., Poesen, J., 2014. Environmental

conditions and human drivers for changes to north Ethiopian mountain landscapes over 145 years.

Science of the Total Environment, 485–486: 164-179.

FOR FIELDWORK

During the fieldwork, the MSc student will stay in villages around Mekelle, and particularly in

rural areas within Tigray; one translator/field assistant will work permanently with him/her.


- The thesis will have to contain an extended summary in English or possibly be written in

English.









- One experienced UGent researcher will help you starting up; possibly other Belgian Master

students will be in the region.















Your local counterpart will be MSc. Etefa Guyassa [email protected]










27

11. Mapping and characterization of gullies with and without check dams

using remote sensing and ground survey, Northern Ethiopia


Coach: MSc Etefa Guyassa (Mekelle University and Ghent University)

Gully formation is the indication of extreme land degradation processes resulted from

different human activities especially associated to agricultural expansion and lack of

sustainable land management. Gullies have various on-site and off-site environmental and

social impacts. Studies on gully dynamics have indicated that the development of gullies

increased in Northern Ethiopia during the second half of 20th century. But implementation of

extensive land management interventions started since late 20th century in the region, what

has decreased the rate of gully developments. Check dam is one of the major soil and water

conservation techniques used in areas where gully formation is a problem. This technology is

believed to have significant effects on gully stabilization. The construction of check dams in

gullies affects the hydrological behaviour of catchments by changing the characteristics of

gullies such as channel bed roughness/cover, slope gradient, and width. Despite their

widespread implementation the effects of check dams on the water balance at catchment scale

are not well understood. This requires the knowledge of the density of check dams and their

impact on the roughness and other characteristics of gullies. Hence, quantification, mapping

and characterization of check dams is required to evaluate the effects of check dams on runoff

in gullies and catchment hydrological behaviour which will further help to design appropriate

developmental schemes such as dam construction. The objectives of this study are (1)

mapping the gullies with and without check dams in Geba catchment; (2) characterization of

selected gullies with and without check dam; (3) extrapolation of the hydrological effects

measured in a few gullies to the wider catchment.

Gully with check dam in the study area

Methodology: Check dams constructed in gullies will be detected by using high resolution

satellite image supplemented by ground survey. Then selected gullies will be characterized for

the roughness, vegetation cover, soil, sedimentation, lithology, slope, cross-section, check

dam type, age, standards and maintenance. Hydrological models will be applied to calculate

the effect of the dams at catchment and subbasin scale (approx. 10-1000 km²).

Current expertise of the promoters with regard to gully systems in the study area

28

Frankl, A., Deckers, J., Moulaert, L., Van Damme, A., Mitiku Haile, Poesen, J., Nyssen, J., 2015. Integrated

solutions for combating gully erosion in areas prone to soil piping: innovations from the drylands of Northern

Ethiopia. Land Degradation & Development, online early view.

Frankl, A., Poesen, J., Mitiku Haile, Deckers, J., Nyssen, J., 2013. Quantifying long-term changes in gully

networks and volumes in dryland environments: the case of Northern Ethiopia, Geomorphology, 201: 254–263.

Frankl, A., Poesen, J., Scholiers, N., Jacob, M., Mitiku Haile, Deckers, J., Nyssen, J.. 2013. Factors controlling

the morphology and volume (V) – length (L) relations of permanent gullies in the Northern Ethiopian Highlands.

Earth Surface Processes and Landforms, 38: 1672–1684.

Frankl, A., Stal, C., Amanuel Zenebe, Nyssen, J., Rieke-Zapp, D., De Wulf, A., Poesen, J., 2015. Detailed

recording of gully morphology in 3D through image-based modelling. Catena, 127: 92-101.

Nyssen, J., Poesen, J., Moeyersons, J., Luyten, E., Veyret-Picot, M., Deckers, J., Mitiku Haile, Govers, G., 2002.

Impact of road building on gully erosion risk: a case study from the northern Ethiopian Highlands. Earth Surface

Processes and Landforms, 27: 1267-1283.

Nyssen, J., Poesen, J., Veyret-Picot, M., Moeyersons, J., Mitiku Haile, Deckers, J., Dewit, J., Naudts, J., Kassa

Teka, Govers, G., 2006. Assessment of gully erosion rates through interviews and measurements: a case study

from Northern Ethiopia. Earth Surface Processes and Landforms, 31(2): 167-185.

Nyssen, J., Veyret-Picot, M., Poesen, J., Moeyersons, J., Mitiku Haile, Deckers, J., Govers, G., 2004. The

effectiveness of loose rock check dams for gully control in Tigray, Northern Ethiopia. Soil Use and

Management, 20: 55-64.

FOR FIELDWORK

During the fieldwork, the MSc student will stay in the market town Hagere Selam; one













region.















Your local counterpart will be MSc Etefa Guyassa [email protected]










29

12. Hydrological balance of forests on a foggy escarpment along

Ethiopia’s Rift Valley

Promoters: Prof. Dr. Jan Nyssen, Dr. Amaury Frankl

Coach: MSc Hailemariam Meaza (Mekelle University and Ghent University), MSc Sofie

Annys (Department of Geography, Ghent University).

The western escarpment of the Ethiopian Rift Valley is subject to eastern air circulations

during winter and spring small rainy season. Forced ascendance of air masses provokes

condensation, cloud formation and possibly rain. Much precipitation is however generated by

the occurrence of beard lichen on trees, particularly on Juniperus procera. “Generally, the

rainfall along this part of the Rift Valley is marginal for the growth of true forest, but similar

to the Afromontane forests in the Bale and Simien mountains, fairly large quantities of

moisture are collected by the forest by trapping clouds or mists which frequently build up

along the escarpment. Epiphytic plants typical for cloud forests such as old man’s-beard

lichen (Usnea spp.) and orchids (for example Polystachya benettiana) can still be found in

the forests” (Aerts et al., 2006). Also in the main rainy season the bearded lichen have been

observed to generate continuous dripping under the trees.

In other places, the forests have been removed, or replaced with plantations of exotics such as

Eucalyptus sp., or Cupressus lusitanica.

The dominant woody vegetation cover along the escarpment was already mapped in detail by

Annys et al. (2016).

Juniperus forest on the escarpment west of Alamata, with lichen apparent on the tree in front

The student will study the spatial distribution of Usnea spp. in relation to the distribution of

its host trees, and measure the precipitation (direct rainfall, throughfall, trapped mist), and

possibly stemflow, in several forests along the escarpment of the Ethiopian Rift Valley

between Maychew and Alamata (Tigray, Northern Ethiopia), in line with procedures that have

already been implemented in the Ethiopian highlands (Obsu et al., 2016). Before and after the

student’s fieldwork period, additional data will be collected by local workers in his/her

absence.

Partitioned rainfall will then be mapped, as well as its contribution to the water balance of

different ecotones.

30

Woody vegetation cover at dominant species level in the study area in 2014 (Annys et al., 2016).

The map exists at high resolution and will be availed to the student.

A manual rain gauge to measure throughfall in a forest in Ethiopia (Obsu et al., 2016).

Dozens of such plastic bottles will be used per site.

References

Aerts, R., Nyssen, J., Mitiku Haile, November, E., Deckers, J., Moeyersons, J. (eds.), 2011.

Excursion guide – post-conference excursion – Extension to the Danakil Depression.

International Association of Geomorphologists, Regional Conference 2011, Addis Ababa, 22

p.

Annys, S., Biadgilgn Demissie, Amanuel Zenebe, Nyssen J., 2016. A Framework for Landsat-

based Mapping of Land and Vegetation Cover in Ethiopia. Photogrammetric Engineering and

Remote Sensing, submitted.

Obsu Hirko Diriba, Edo Beressa Bedasso, Habenom Haileselassie, Nyssen, J., Frankl, A., 2016.

31

The eco-hydrology of eucalypt stands in Central Ethiopia and implications for soils. Soil Use

and Management, submitted.

FOR FIELDWORK

During the fieldwork, the MSc student will stay in the towns of Korem and Alamata; one













region.















Your local counterpart will be MSc Hailemariam Meaza

[email protected]










32

13. Contemporary and historical rates of floodplain sedimentation in

Lake Tana basin (Ethiopia)


Coach: MSc Hanibal Lemma (Bahir Dar University and Ghent University)

Introduction

In the Lake Tana Basin (LTB), extensive lacustrine plains were created when the Lake Tana

reached its maximum extent (Poppe et al., 2013; Vijverberg et al., 2009). Terraces and river

deltas in the basin suggest that the lake extent decreased; the current lake area is 3074 km2 as

compared to the ancient extent of 6514 km2 (Poppe et al., 2013; Rzóska, 1976). However,

parts of these lacustrine plains (once it was the bed of Lake Tana) adjacent to the rivers and

the lake are subjected to periodic flooding and sediment deposition, and form a wide area of

floodplains.

Those floodplains can buffer the transport of sediment as it is mobilized from the upstream

parts of the catchment. Sedimentation on the river floodplains during overbank floods can

result in significant reduction of the suspended sediment load transported by a river and can

thus represent an important component of the catchment sediment budget (Walling & Owens,

2003). The storage effects of floodplains may, therefore, complicate the interpretation of

downstream sediment yields in terms of upstream sediment mobilization by attenuating the

record of sediment delivery from hillslopes and sediment transfers within the upstream

drainage basin (Walling et al., 1998).

Although it is generally recognized that floodplain systems may provide an important sink for

suspended sediment during periods of inundation, this role has attracted little attention in

previous sediment budget studies in LTB (Maes, 2012; Engida, 2010; SMEC, 2008).

However, Hanibal et al. (2015) estimated that the conveyance losses associated with overbank

deposition over the floodplains was on average 32% of the total sediment from the upstream

hilly catchment.

Floods and sedimentation along the Gumara floodplain in LTB

Understanding the significance of floodplain conveyance losses to sediment budget is

important if sediment yield data are to be used to interpret on-site rates of soil loss and the

implementation of soil conservation measures is to be meaningfully assessed (Walling et al.,

2001). Hence, the main purpose of the study is to quantify rate of floodplain deposition in

order to understand the process associated with the delivery of fine sediment through the

catchment system.

33

Methodology

Field measurements of water and sediment discharge will be combined to estimate rates of

transport and the fate of water and sediment along the river reach.

• Monitoring SSC during peak flood events as well as along the river reach

• Floor tiles as sediment trap in different land uses and different locations

perpendicularly to the river

• Use of radionuclide (137Cs or 210Pb) and study of anthropogenic soil horizons (around

residence area) to assess historical deposition

References

Engida, A. N. (2010). Hydrological and suspended sediment modeling in the Lake Tana Basin, Ethiopia. PhD

thesis, Universite Joseph-Fourier - Grenoble I.

Hanibal L., Teshager A., Mekete D., Derbew F., EnyewA., J. Poesen & J. Nyssen (2015). Sediment budget of

Lake Tana and the role of lacustrine plains. In Enyew Adgo, Mekete Dessie, Jan Nyssen (Eds.), Tropical lakes in

a changing environment: water, land, biology, climate and humans (p.137). Bahir Dar, Ethiopia

Maes, R. (2012). Spatial and temporal patterns of sediment dynamics and sediment budget for Lake Tana

Catchment, Ethiopia. MSc thesis, Katholieke Universiteit Leuven and Vrije Universiteit Brussel, Faculteit

Wetenschappen.

Poppe, L., Frankl, A., Poesen, J., Admasu, T., Dessie, M., Adgo, E., Deckers, Jozef & Nyssen, J. (2013).

Geomorphology of the Lake Tana basin, Ethiopia. Journal of Maps, 9, 431–437.

Rzóska, J. (Ed.). (1976). The Nile, Biology of an Ancient River (Vol. 29). Dordrecht: Springer Netherlands.

SMEC. (2008a). Hydrological Study of the Tana-Beles Sub-Basins: Main Report. Ethiopia: Ministry of Water

Resources, Addis Ababa.

Vijverberg, J., Sibbing, F. A., & Dejen, E. (2009). Lake Tana: Source of the Blue Nile. The Nile, 89, 163–192.

Walling, D. E., Collins, A. L., Sichingabula, H. M., & Leeks, G. J. L. (2001). Integrated assessment of catchment

suspended sediment budgets: a Zambian example. Land Degradation & Development, 12(5), 387–415.

Walling, D. E. and P. N. Owens (2003). The role of overbank floodplain sedimentation in catchment

contaminant budgets. Hydrobiolia 494:83-91

Walling, D.E.; Collins, A.L.; Leeks, G.J.L. (1998). The role of channel and floodplain storage in the suspended

sediment budget of the River Ouse, Yorkshire, UK. Geomorphology 22:225-242

Walling, D.E.; Collins, A.L.; Sichingabula, H.M.; G.J.L. Leeks (2001). Integrated assessment of catchment

suspended sediment budget: A Zambian example. Land Degradation and Development 12:387-415.

FOR FIELDWORK

During the fieldwork, the MSc student will stay in Bahir Dar and small towns such as Woreta

or Wanzaye; one translator/field assistant will work permanently with him/her.





- Environment for the fieldwork: tropical climate (June/September is the rainy season); other

culture, totally different food, other norms for comfort; often no electricity; telecommunication

is difficult; only a few busses per day; the student will often move on foot (heavy rains possible

in the afternoon). But also: friendly, dynamic people and breathtaking landscapes, and a unique

experience.



region.











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Your local counterpart will be MSc Hanibal Lemma [email protected]







35

14. Gully erosion rates and efficiency of gully control measures

worldwide

Promoters: Dr. Amaury Frankl and Prof. Dr. Jan Nyssen

“Physical Land Resources” students are invited to carry out research on topics of gully

erosion rates and efficiency of gully control measures in their home country; it a main

expertise of the Physical Geography research group.

Depending on the conditions in your country, an appropriate topic will be developed in

agreement with the promoters.

See some examples of publications based on previous master thesis research:

- Frankl, A., Deckers, J., Moulaert, L., Van Damme, A., Mitiku Haile, Poesen, J.,

Nyssen, J., 2016. Integrated solutions for combating gully erosion in areas prone to

soil piping: innovations from the drylands of Northern Ethiopia. Land Degradation &

Development, 27(8): 1797–1804.

- Lannoeye, W., Stal, C., Etefa Guyassa, Amanuel Zenebe, Nyssen, J., Frankl, A., 2016.

The use of SfM-photogrammetry to quantify and understand gully degradation at the

temporal scale of rainfall events: an example from the Ethiopian drylands. Physical

Geography, 37(6): 430-451.

- Nyssen, J., Seifu Gebreselassie, Romha Assefa, Deckers, J., Amanuel Zenebe, Poesen,

J., Frankl, A., 2016. Boulder-faced Log Dams as an Alternative for Gabion Check

Dams in First-order Ephemeral Streams with Coarse Bed Load in Ethiopia. Journal of

Hydraulic Engineering, online early view.

- Frankl, A., Poesen, J., Mitiku Haile, Deckers, J., Nyssen, J., 2013. Quantifying long-

term changes in gully networks and volumes in dryland environments: the case of

Northern Ethiopia, Geomorphology, 201: 254–263.

- Frankl, A., Poesen, J., Scholiers, N., Jacob, M., Mitiku Haile, Deckers, J., Nyssen, J..

2013. Factors controlling the morphology and volume (V) – length (L) relations of

permanent gullies in the Northern Ethiopian Highlands. Earth Surface Processes and

Landforms, 38: 1672–1684.

- Frankl, A., Stal, C., Amanuel Zenebe, Nyssen, J., Rieke-Zapp, D., De Wulf, A.,

Poesen, J., 2015. Detailed recording of gully morphology in 3D through image-based

modelling. Catena, 127: 92-101.

- Monsieurs, E., Poesen, J., Mekete Dessie, Enyew Adgo, Verhoest, N., Deckers, J.,

Nyssen, J., 2015. Effects of drainage ditches and stone bunds on topographical

thresholds for gully head development in North Ethiopia. Geomorphology, 234: 193-

203.

- Nyssen, J., Poesen, J., Moeyersons, J., Luyten, E., Veyret-Picot, M., Deckers, J.,

Mitiku Haile, Govers, G., 2002. Impact of road building on gully erosion risk: a case

study from the northern Ethiopian Highlands. Earth Surface Processes and Landforms,

27: 1267-1283.

- Nyssen, J., Poesen, J., Veyret-Picot, M., Moeyersons, J., Mitiku Haile, Deckers, J.,

Dewit, J., Naudts, J., Kassa Teka, Govers, G., 2006. Assessment of gully erosion rates

through interviews and measurements: a case study from Northern Ethiopia. Earth

Surface Processes and Landforms, 31(2): 167-185.

- Nyssen, J., Veyret-Picot, M., Poesen, J., Moeyersons, J., Mitiku Haile, Deckers, J.,

Govers, G., 2004. The effectiveness of loose rock check dams for gully control in

Tigray, Northern Ethiopia. Soil Use and Management, 20: 55-64.

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