Exploring Kikuletwa South

Transcription

1 Exploring Kikuletwa South Tour with James (FTK) to the Kikuletwa (S) and Chem Chem region On 2 December 2014 the plan was to visit Chem Chem and get to know more about the flooding extent over there. Unfortunately the road was blocked by a high water level because of heavy rains the night before. Thus it was decided to explore the Kikuletwa and try to find the point where the Kikuletwa transforms from a small channel to a wide one. James Ashire is the village manager of FT Kilimanjaro. He arranged that a local elderly called Ashraf joined us as our guide. During our trip there were two points of attention: 1. measuring the profile of the small part of the Kikuletwa after the bifurcation of the Ronga and the Kikuletwa. At the point of bifurcation, a small part of the discharge flows in a small channel; the first part of Kikuletwa (S). 2. How far downstream will this small part of the Kikuletwa open up? In the table below the visited locations are presented and those locations are shown in Figure 1. In this report the important waypoints will be discussed one by one. As shown in Table 1. Figure 1: Waypoints 1

2 Table 1: Waypoints WAYPOINT DESCRIPTION 01 River passing Kikuletwa (S) 02 Point of profile measurement Kikuletwa House of our guide:, starting point 05 Stream within the floodplain area, very low- no velocity; no connection with the Kikuletwa River. 06 Small part Kikuletwa river Irrigation channel with banks, manmade; dry 09 Another irrigation channel with bank manmade; dry 10 New constructed road streambed 13 Irrigation channel Village along the Kikuletwa Confluence of the Kikuletwa and Tributarie Kikuletwa (S) 20 Point of measuring Kikuletwa (S) 21 2

3 1 WAYPOINT 01 RIVER PASSING KIKULETWA After picking up Tamari and the elder named Ashraf at Kiruwani, we arrived at the river passway crossing the Kikuletwa and entering Chem Chem. Because of a lot of rain in the night the water level was unfortunately too high. We could not enter Chem Chem by car. We thus decided to do some measurements and return to Kiruwani were we would try to cross the river. Cornel walked to the other side with his boots and the water almost entered his boots. So we can conclude that the water was somewhat 80 or 90 cm high (at the less deepest location). Table 2: Registration of waypoint 01 LOCATION Crossing kikuletwa to Chem Chem GPS COORDINATE/WAYPOINT NUMBER 01 CURRENT WATER LEVEL (OBSERVATION) 0.9 m deepest. WIDTH OF RIVER CURRENT wide FLOODING PRESENT? yes TYPE OF WATER WAY Slingerend, met vegetatie n=0.045 TYPE OF FLOOD PLAIN Struikgewas n=0.050 BIG ELEVATION DIFFERENCES? No DRY OR WET? Dry 3

4 DEPTH [M] Chemchem region WAYPOINT 02/03 MEASUREMENT SOUTHWARDS CROSSING AND VELOCITY MEASUREMENT This spot was right after the wide part were you normally can cross the river to Chem Chem. We decided to walk 300 m and do a measurement over there. Ashraf told us that the river from this point was almost the same until the reservoir. We measured the river and it was at its top 26,5 m wide. The river itself was at this moment 8 m wide. The river was too deep to do a depth measurements (no boats were present). The water still had 3.5 m left to rise until it would flood surrounding land. We also performed a velocity measurement (see Table 3: Registration of waypoint 03Table 3). We took 20 meters and measured the following: big piece of wood sec by Jaap and 50.8 sec by Wessel Small piece of wood sec by Jaap and sec by wessel. 4 2 CROSS-SECTION KIKULETWA AT WP= DISTANCE OVER X [M] Figure 2: Cross-section Kikuletwa at wp 03 Table 3: Registration of waypoint 03 LOCATION 200 meters downstream of Chem Chem crossing point GPS COORDINATE/WAYPOINT NUMBER 02 WIDTH OF RIVER CURRENT 8 m FLOODING PRESENT? no WATER LEVEL DURING FLOODING 3,5 +? WIDTH OF RIVER DURING FLOODING 26,5 m TYPE OF WATER WAY Slingerend, met vegetatie n=0.045 TYPE OF FLOOD PLAIN Struikgewas n=0.050 SURFACE VELOCITY 20/( )/4=0.38 m/s HEIGHT OF BANKS LEFT 3.5 m TYPE OF AGRICULTURE Bushes/ none TYPE OF HOUSING - TYPE OF FLORA Trees, bushes BIG ELEVATION DIFFERENCES? yes DRY OR WET? dry 4

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6 3 WAYPOINT 05 MSITUA TEMBO WATER When walking to the Kikuletwa we had to cross a small river coming from the mountains at the Msitua Tembo side. Ashraf said that this small river is not related to the river flooding (in this area). He also told us that during the long floods the water could rise to the treeline just in front of the village. Thus uptil at least this WP. It happens on average twice a year. Even sometimes during the short rains. In the past more trees where present in this area, but they are all used for making charcoal. Table 4: Registration of rivers LOCATION Small river coming from Msitua Tembo mountains/ flood line Kiruani GPS COORDINATE/WAYPOINT NUMBER 05 CURRENT WATER LEVEL (OBSERVATION) ~0.4 m WIDTH OF RIVER CURRENT 4 meter FLOODING PRESENT? yes WATER LEVEL DURING FLOODING Until treeline SURFACE VELOCITY slow BIG ELEVATION DIFFERENCES? no DRY OR WET? wet 6

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8 DEPTH [M] Chemchem region WAYPOINT 06 KIKULETWA CROSSING After a long walk through wide fields we arrived at the Kikuletwa. It was as narrow as right after the bifurcation point. A cross-sectional profile was derived by use of a log across the river. Also the speed and the E.C. was measured. The E.C. meter gave a value of 947µ Sv and the temperature was 25.4 C. CROSS-SECTION KIKULETWA AT WP=06 1 0,5 Water depth 0-0, , 5 1 1, 5 2 2, 5 3 3, 5 DISTANCE OVER X [M] Figure 3: Cross-section of the Kikuletwa at WP 06 Table 5: Registration of waypoint 06 LOCATION Kikuletwa GPS COORDINATE/WAYPOINT NUMBER 6 CURRENT WATER LEVEL (DEPTH SONAR) 90 cm WIDTH OF RIVER CURRENT 3 m FLOODING PRESENT? no TYPE OF WATER WAY Small creek, straight SURFACE VELOCITY 10/26.73=0.37 m/s DEPTH VELOCITY (0.4*D) 04*0.9=0.36 m/s HEIGHT OF BANKS LEFT 50 cm TYPE OF AGRICULTURE Banana trees TYPE OF FLORA Banana trees, little trees BIG ELEVATION DIFFERENCES? little 8

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10 5 WAYPOINT 08 BRIDGE OVER DRY GULLY After crossing the Kikuletwa we arrived in the Chem Chem area. We arrived at a dry gully. Achraf told us that it was constructed by the villagers to divert water from the Kikuletwa to other land, but unfortunately the gully was too high and the water couldn t flow in. It doesn t flood in this area. Table 6: Registration of rivers LOCATION Dry gully chem chem GPS COORDINATE/WAYPOINT NUMBER 8 CURRENT WATER LEVEL (OBSERVATION) No water FLOODING PRESENT? no WATER LEVEL DURING FLOODING none 10

11 6 WAYPOINT 09 ANOTHER DRY GULLY Walking further we crossed another dry gully. It was a diversion of the gully mentioned at WP 08. This gully was also too high. Ashraf told us that the gully was man made, but it looked like a natural way because it was meandering. Also trees were next to the gully Table 7: Registration of rivers LOCATION Dry gully Chem Chem 2 GPS COORDINATE/WAYPOINT NUMBER 9 CURRENT WATER LEVEL (OBSERVATION) None FLOODING PRESENT? no 7 WAYPOINT 10 ROAD OF CHEM CHEM Walking further we arrived at the newly constructed road in Chem Chem. We asked what the flood reach was and it was told that it was some 200 meters from where we were standing now. Form this waypoint, 45 degrees and 200 meters away the water would come. 11

12 8 WAYPOINT 11 NEWLY DUG GULLY CROSSING THE ROAD We walked along the road and found a newly dug gully. We had seen the gully before when we drove there earlier with Gerbert, but this time it was bigger. Local villagers told us that the water is distracted from the Ronga and led to some rice fields further down. Table 8: Registration of rivers LOCATION Gully crossing the road GPS COORDINATE/WAYPOINT NUMBER 11 CURRENT WATER LEVEL (OBSERVATION) 30 cm WIDTH OF RIVER CURRENT 50 cm FLOODING PRESENT? No TYPE OF WATER WAY (SEE 4.2.3) Small gully 12

13 9 WAYPOINT 12 (OLD?) RIVER BED This point looked very much like an old river bed. It was deeper in the middle, had higher sides and was for a long stretch surrounded by trees. Achraf told us that in the rain season a small amount of water flows through it. It s somewhat 30 meters wide. The old river bed is next to a very wide field with any irrigation channels. The channels are dry now because of the construction of the road, but normally water would flow through. Table 9: Registration of rivers LOCATION Old river bed GPS COORDINATE/WAYPOINT NUMBER 12 CURRENT WATER LEVEL (OBSERVATION) None FLOODING PRESENT? No 13

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15 10 WAYPOINT 13 ANOTHER DRY GULLY This is the same gully we crossed at WP 09. It s 3 meter wide and 40 cm deep. No water is in it. Table 10: Registration of waypoint 13 LOCATION Dry gully GPS COORDINATE/WAYPOINT NUMBER 13 CURRENT WATER LEVEL (OBSERVATION) none WIDTH OF RIVER CURRENT 3 m HEIGHT OF BANKS LEFT 40 cm 11 WAYPOINT 14 VILLAGE MISWAKINI We arrived at a small village called Miswakini which exists of 10 houses. 15

16 12 WAYPOINT 15 THE KIKULETWA We arrived again at the Kikuletwa when walking in between two villages close to each other. The river was partly dammed to divert some water. 16

17 13 WAYPOINT 16 A BRANCH OF THE KIKULETWA This was a branch of the Kikuletwa next to another part of Miswakini village with some houses. It is 1 meter wide and has a slow flow. We asked some local villagers some questions: In the past when the Kikuletwa was bigger it never flooded in this area. We asked them about the case that more water would be flowing through the kikuletwa. Their response was that this would be no problem, the sand dug out could then be used to build small dikes around it. But their concern was with the rice fields downstream. If the water would be to high the water in the rice fields couldn t not be flown through by natural flow. Little weirs should be build then. 14 WAYPOINT 17 IRRIGATION CHANNEL FROM RICEFIELDS An irrigation channel returning from the rice fields. Looks natural. 17

18 15 WAYPOINT 18 WIDE DRY BRANCH This is a wide (old) dry branch of the kikuletwa. The water from the previous mentiond irrigation channel (WP 17) is diverted away from this branch into another dry branch next to this one. The (dry) branch is 8 meter wide and 1.5 m high. It has a parabolic profile. Next to the dry branch another branch is present which is 10 m wide and 2 m high. Water flows through it. Table 11: Registration of rivers LOCATION Wide dry branch GPS COORDINATE/WAYPOINT NUMBER 18 18

19 16 WAYPOINT 19 KIKULETWA STREAM This part of the Kikuletwa is surrounded by a lot of treas. The Kikuletwa streams relatively deep compared to ground level (3m). The water from the irrigation channel has already joint the Kikuletwa. From this point on the Kikuletwa gets a wider profile. Table 12: Registration of rivers LOCATION Kikuletwa stream GPS COORDINATE/WAYPOINT NUMBER 19 FLOODING PRESENT? no TYPE OF FLORA Lots of trees 19

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21 DEPTH [M] Chemchem region WAYPOINT 20 MEASUREMENT OF KIKULETWA A few meters downstream of WP 19 measurements were taken. At this point the Kikuletwa gets a wider profile. From the Msitua Tembo side a wide branch joins the Kikuletwa. There is no water flowing through now. But it will just after it rained on the mountains at Msitua Tembo. The river is 5.5 meter wide. The total width of the river bed is 18.4 meter. The river profile is shown below. The river is 0.8 m deep in the middle and can still rise 3 meters. The E.C. meter gives a value of 954 µsv and a temperature of 26.3 C. Also the velocity was measured. At the edge there is a 1.5 meter vertical and then an inclined profile towards the flowing water. CROSS-SECTION KIKULETWA AT WP20 3,5 3 2,5 2 1,5 1 0,5 0-0, DISTANCE OVER X [M] Figure 4: Cross section kikuletwa at wp20 Table 13: Registration of rivers LOCATION Measurement of kikuletwa GPS COORDINATE/WAYPOINT NUMBER 20 CURRENT WATER LEVEL (OBSERVATION) 0.8 m CURRENT WATER LEVEL (DEPTH SONAR) 0.8 m WIDTH OF RIVER CURRENT 5.5. m FLOODING PRESENT? No WATER LEVEL DURING FLOODING? WIDTH OF RIVER DURING FLOODING? SURFACE VELOCITY 20/( )/2=0.34 m/s DEPTH VELOCITY (0.4*D) 0.4*0.8=0.32 m/s HEIGHT OF BANKS LEFT 3 m TYPE OF FLORA trees BIG ELEVATION DIFFERENCES? yes 21

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