2015 Fig Working Week Sofia Bulgaria 17Th

26-05-2015

2015 FIG WORKING WEEK SOFIA BULGARIA 17 TH – 21 ST MAY, 2015

• GEOGRAPHIC INFORMATION SYSTEMS BASED URBAN DRAINAGE EFFICIENCY FACTORS

(PAPER 7526, TS03D - Disaster and Land Management ) Commission: 3 This is a peer reviewed paper.

BY DR. A.C. CHUKWUOCHA 1 AND MRS NGOZI AC-CHUKWUOCHA 2

1 Department of Surveying and Geoinformatics, Federal University of Technology Owerri, Nigeria 2 Department of Environmental Technology, Federal University of Technology Owerri, Nigeria 1 [email protected]; 2 [email protected]

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1.0 INTRODUCTION • The dangers of flooding are becoming increasingly real across the globe as a consequence of the twin issues of urbanization and global warming. • Urban areas are springing up steadily in the developing world. The United Nations projects that by 2030 half of all of Africa’s population will live in urban centers.1 • Urbanization has been reported to aggravate flooding by creating impervious ground surfaces which reduce infiltration and constructions restrict where flood water can go.

INTRODUCTION contd. • It is estimated that over the years more than 60% of Nigerian states have recorded some form of serious flooding. It is noted that at least 20 per cent of the total national population is at risk of one form of flooding or another. 4

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STUDY AREA • The study area is the urban area of Owerri, Imo State, South East Nigeria and its environs. Owerri is the capital city of Imo State, south- eastern Nigeria. Owerri with a population of about 150,000 situates between 50 20'N, 60 55'E in the south-western corner and 50 34'N, 70 08'E in the north-eastern corner. • Owerri previously considered a non-flooding area now floods continuously. The drainages generally follow the road edges and are constructed to protect the paved roads, and not necessarily to mitigate flooding.

Fig. 1a Map of Nigeria with LGAs, showing Imo State South East Nigeria in deep red colour 6

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450000 .000000 462000 .000000 474000 .000000 486000 .000000 498000 .000000 510000 .000000 522000 .000000 534000 .000000 546000 .000000 558000 .000000 .000000 .000000 216000 216000 .000000 .000000 Ideato North Orsu 207000 207000 .

Okigwe Legend

Orlu Study area boundary

.000000 Ideato South .000000 imo state Unuimo 198000 198000 LGAS Aboh-Mbaise Ahazu Mbaise Oru West Ehime Mbano Nkwere Ezinihitte Mbaise Ideato North

.000000 .000000 Ideato South Nwangele Ikeduru

189000 Mjaba 189000 Isiala Mbano Oru East Isu Isu Mbaitolu Isiala Mbano Ehime Mbano Oguta Mjaba Ngor-Okpala Nkwere .000000 .000000 Nwangele Obowo 180000 180000 Oguta Ohaji/Egbema Mbaitolu Obowo Okigwe Orlu Orsu Ikeduru Oru East .000000 Ahazu Mbaise .000000 Oru West Owerri Municipal 171000 171000 Owerri North Owerri West Unuimo Subcatchments Owerri Municipal

.000000 .000000 Area Ezinihitte Mbaise 320.05350896 360.276453488 162000 162000 Owerri North Text 461.573081563 Owerri West 466.236801963 Aboh-Mbaise 487.301701449 Ohaji/Egbema 495.270605097 495.736435724

.000000 .000000 615.032625947 628.232693178

153000 153000 631.90240374 652.461431266 653.824198211 683.164517103 713.981928217 725.350858253

.000000 .000000 744.662830032

Ngor-Okpala 869.883640897

144000 144000 886.316975499 1157.54464801 1158.68691022 1251.65930107 1477.02156835 1942.42028488 .000000 .000000 135000 135000

450000 .000000 462000 .000000 474000 .000000 486000 .000000 498000 .000000 510000 .000000 522000 .000000 534000 .000000 546000 .000000 558000 .000000 Scale: 1:250,000

30 15 0 30 Kilometers

Fig. 1b Map of Imo State with LGAs, showing the project area in red

Fig 1c: Map of the Project Area 8

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2.0 LITERATURE

2.1 Literature in Jeddah - Western Saudi Coast, Kingdom of Saudi Arabia • Al-Saud M. (undated) reports on the use of Remote Sensing and Geographic Information System to analyze drainage systems in flood occurrence in Jeddah - Western Saudi Coast, Kingdom of Saudi Arabia. The paper reports that 1:50,000 topographic maps of 20m contour interval together with DEM were used to extract the related parameters for drainage systems after delineating the drainage flow routes and their basins directly in the GIS in the study area covering about 1947km 2

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2.2 Literature in Kukatpally Municipality, India • Rao, D. R. M., Ahmed, Z., Reddy, K. R. M., Raj, E. (2013) a technical paper on the selection of drainage network using Raster GIS in Kukatpally Municipality, India finds that for efficiency, selection of drainage layout should be based on a good understanding of topography. The paper concludes that alignment of sewers and storm water drains should follow natural drainage patterns considering topography, land use, land cover and right of way for both drainage and economic efficiency.

2.3 Literature in University of Zimbabwe • A 2002 paper reports on the assessing of the efficiency of the then newly constructed drainage system of the University of Zimbabwe by combining a Digital Elevation Model (DEM) with a rainfall-runoff model based on the Soil Conservation Service - South African Manual (SCS -SA) concluded that While the drainage sizes were seen to be suitable, visual on screen inspection showed that the orientation of the drains required a lot of improvement. It appeared that overall, the drain orientation was dictated by the orientation of the road network and position of building lines 5.

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2.4 Literature in New Orleans Drainage Pumping Station No 4 Basin • Giron (2005) reporting on the development of a SWMM-GIS flood model for New Orleans Drainage Pumping Station No 4 Basin, concludes that high intensity rain events flooding might be caused by inadequate inlet capacity, and not just by lack of capacity in the main trunk system or insufficient pumping capacity. The time it takes for water to be drained into the sewer system is critical. If the inlet is inadequate, very heavy storms even over a very short period can produce flooding and significant damage. The point of the inlets as an efficiency factor in drainage design is clear.

2.5 THEORETICAL FRAME WORK

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2.51 GENERAL SUB-CATCHMENT LAYOUT

Fig. 2 General properties of a sub-catchment

GENERAL PROPERTIES OF A SUB-CATCHMENT • Fig 2 illustrates the general properties of a sub- catchment. • The natural drainage line flows between the two leaves of each sub-catchment. This is the basic unit of each landscape. • When an urban area is planned the drainage of the area should be planned in consideration of the lay out of the sub-catchment. The design should anticipate the capture of runoff from the landscape before it builds up enough to create a flood or to erode the landscape. These drainage plan should convey captured runoff to the free flowing natural flow route.

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64 N 32 NW 128 NE

16 W 1 E

8 SW 2 SE 4 S

Fig. 7 Flow Direction Scheme

141 140 140 141 142 142 141 142

139 138 137 139 139 139 139 140

138 135 135 136 137 136 137 139

134 134 132 134 135 134 136 138 2 2 4 8 4 4 4 8 131 131 129 133 133 132 134 137 2 4 4 8 2 4 8 8 128 127 126 132 131 130 132 133 4 2 4 8 2 4 8 2 126 123 124 126 128 129 131 133 4 2 4 8 2 4 8 8 124 120 125 127 129 129 130 132 DIGITAL ELEVATION MODEL 2 2 4 8 2 4 8 4 2 4 4 8 8 8 16 16 2 4 16 16 16 16 16 16 1 0 16 32 32 32 16 16 FLOW DIRECTION SCHEME Fig. 8 Digital Flow Direction Scheme

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1 1 1 1 1 Figure 9 Flow Accumulation Grid 1 1 1 1 1 1 1 1 1 Figure 10 Drainage Route Cells

Runoff Flow Routes

Figure 11 Drainage Route

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Layout of efficiency factored landscape drainages

Fig. 12 Layout of efficiency factored landscape drainages

3.5 SCHEME OF DRAINAGE DESIGN

• TERTIARY DRAINAGES: The layout is planned in such a way that the runoffs are captured by tertiary drainages which are aligned near parallel to primary drainage lines. The tertiary drainage lines run across the slope direction of the landscape. The tertiary drainages ensure immediate capture of runoff from each plot or across each road before they build up to flood or erode.

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SECONDARY AND PRIMARY DRAINAGE NETWORKS • SECONDARY DRAINAGES: The secondary drainage lines are aligned along the slope directions. They collect runoffs from the tertiary drainages and empty them into the primary drainages which convey the runoffs away from the sub-catchment.

• PRIMARY DRAINAGES: They convey runoff from Secondary drainages. With the area of the sub- catchment known the sizes of the drainages can be calculated with a good knowledge of the designed peak rain storm event.

2.5 Drainage Efficiency Factors From the Literatures the drainage efficiency factors would include: Location of Drainage Horizontal Alignment Vertical Alignment Size of Drainage Inlet numbers and Positions 24

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• 3.0 MATERIALS AND METHODS

FLOW CHART OF THE GEOGRAPHIC INFORMATION SYSTEMS BASED URBAN DRAINAGE EFFICIENCY FACTORS

ARCMAP/ARCHYYDRO DATA PROCESSING

INPUT DATA Topographical data of the project area

DIGITAL DATA CAPTURE Scanning, Georeferencing and Digitizing of topographical maps

DATA PROCESSING Check for Adequacy of Topo Data, Errors and Conversion of Digital Raster Data Sinks in the Digital to Digital Elevation Model (DEM) Elevation Model (DEM)

Processing the DEM to produce Flow Direction Grid

Processing the Flow Direction & Processing the Flow Direction Grid Flow Accumulation Grids to to produce Flow Accumulation Grid produce the Stream Segmentation Grid (Stream Link Grid) Processing the Flow Direction Grid and the Processing the Flow Direction Grid and the Stream Link Grid to produce the Drainage Line Feature Class Stream Link Grid to produce the sub- catchment feature class

Overlay of the Natural Drainage Lines and the delineated sub-catchments into the map of the project area to compare position and alignment of constructed drainages against the GIS determined routes

PROVISION OF BASIC DRAINAGE INFORMATION AND STATEMENT ON THE ADEQUACY OR OTHERWISE OF THE DRAINAGE SYSTEM OF THE PROJECT AREA Fig. 3 Flow Chart of the Project Methodology 26

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3.1 DATA ACQUISITION • The research essentially involved the analysis of topographic data of the about 186.024 Sq. Km, (18,602.38 Ha ) project area. • Thankfully topographic maps of the wide area of coverage of Owerri Nucleus area were made available by the Imo State Surveyor General and the Head of the Survey Department, Owerri Capital Development Authority.

500000 .000000 505000 .000000 510000 .000000 515000 .000000 520000 .000000 .000000 .000000 174000 - 174000 .000000 .000000 171000 171000 .000000 .000000 168000 168000 .000000 .000000 165000 165000 .000000 .000000 162000 162000 .000000 .000000 159000 159000 Scale: 1:100,000 52.5 0 5 Kilometers .000000 .000000

500000 .000000 505000 .000000 510000 .000000 515000 .000000 520000 .000000 156000 156000

Fig. 4 Georeferenced Topo Maps of the Project Area in mosaic 28

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THE RESULTING DIGITAL CONTOUR OF THE PROJECT AREA

498000 .000000 502000 .000000 506000 .000000 510000 .000000 514000 .000000 518000 .000000 .000000 .000000 174000 174000

1 1 7 9 1 1 1 7 1 2 2 2 1 2 1 6 1 7 7 5 1 7 0 0 8 9 6 7 5

6 4 7 8 1 2 9 3 3 6 7 6 1 0 7 0 1 7 9 3 7 1 1 8 1 0 2 5 6 2 2 9 8 6 9 9 2 2 2 4 1 1 1

8 1 7 1 1 1 4

7 1 1 7 5 1 1 7 5 8 1 1 8 11 0 1 2 5 7 8 1 9 3 1 6 7 6 2 8 2 7 2 3 8 1 7 1 .000000 .000000 7 7 8 7 9 8 9 1 1 7 5 1 0 2 1 1 2 7 1 1 2 9 0 9 1 7 1 1 2 5 9 9 2 7 2 2 1 7 1 2 9 7 77 5 6 6 9 1 1 3 1 6 6 9 8 2 0 7 4 2 7 7 8 1 1 1 9 6 2 1 1 1 5 9 1 4 4 1 1 1 1 9 0 7 2 4 1 7 8 0 4 5 2 2 1 97 7 7 7 6 5 8 1 1 171000 4 7 9 171000 4 7 7 2 4 12 7 9 72 4 6 7 8 1 1 11 71 7 2 3 8 1 1 4 2 0 107 - 6 1 1 3 6 8 70 2 0 7 22 1 1 1 8 67 0 8 9 7 2 2 2 12 1 1 6 7 1 1 2 1 7 1 6 2 8 1 1 4 6 9 7 2 6 1 8 9 0 2 9 2

5 9 6 7 3 1 5 1 69 8 5 3

6 4 1 1 6 4 7 2 1 0 6 3 1 1 1 1

8 6 6 123 5 6 1 1 7 9 3 7 8 7 7 0 2 2 0 6 0 5 5 1 5 7 3 1 1 1 8 1 1 1 2 6 4 6 7 1 2 8 9 2 2 1 1 0 9 4 8 7 3 1 3 4 3 4 8 1 7 7 7 5 1 2 1 7 1 4 1 9 1 3 12 3 2 2 1 4 25 0 7 1 7 6 6 5 5 5 3 0 1 7 .000000 7 9 0 7 .000000 7 4 1 5 1 109 7 2 9 22 20 6 6 7 1 3 7 6 66 9 9 3 9 2 23 11 7 7 5 1 1 1 0 1 0 6 0 0 72 6 8 1 70 2 6 3 114 1 1 71 1 1 4 7 6 5 6 7 8 1 1 3 6 11 1 7 9 5 2 1 2 1 1 0 1 3 0 8 0 9 1 1 1 6 6 8 1 3 1 0 10 168000 6 5 168000 7 7 8 1 9 9 15 4 1 70 6 6 2 0 7 7 1 7 71 67 0 7 10 1 115 6 117 11 1 2 0 9 1 11 1 0 6 6 6 4 96 3 12 1 9 7 8 3 7 3 6 7 9 3 9 6 8 0 9 2 98 1 2 1 6 6 6 1 7 2 8 4 0 1 2 1 6 6 6 1 7 8 9 1 121 7 8 2 1 4 9 1 5 6 6 1 4 1 2 4 1 7 70 1 5 2 9 1 2 7 7 7 7 8 2 6 7 1 0 0 8 1 6 8 0 5 0 7 0 1 7 0 6 6 4 6 7 7 5 62 86 2 69 3 0 4 6 7 8 2 1 5 66 1 8 8 9 1 6 6 8 67 7 6 4 1 6 3 0 7 3 3 9 7 71 9 6 1 0 0 6 .000000 2 .000000 6 7 7 6 67 8 8 1 7 1 6 6 6 8 1 8 5 9 7 70 8 8 0 6 6 6 6 0 8 3 0 7 7 5 70 6 7 6 90 8 1 7 0 6 6 6 7 0 4 6 5 0 6 8 0 2 0 1 7 8 7 0 1 8 1 6 6 8 8 7 6 6 165000 6 6 6 165000 5 7 70 7 6 6 6 9 8 9 0 6 2 8 8 9 9 2 1 7 6 9 6 6 8 9 7 6 0 0 6 0 6 6 4 0 6 9 6 7 4 8 8 70 7 6 5 7 5 1 6 6 6 6 6 8 2 8 2 5 6 9 7 9 9 6 4 1 6 6 6 6 6 6 4 8 9 6 5 9 8 1 0 1 9 7 9 8 6 6 0 6 9 6 62 66 6 6 0 6 6 7 4 8 5 9 6 6 3 6 58 7 8 0 1 9 6 8 6 4 9 8 7 2 2 6 0 8 6 5 6 7 4 5 6 6 0 6 6 6

7 6 8 6 2 0 6 9 5 5 1 6 69 0 64 8 8 5 9 9 6 7 70 7 6 2 6 0 6 6 7 1 0 5 6 0 9 9 8 5 5 9

6 7 7 6 6 3 7 6 1 6

.000000 .000000 5 8 8 6 8

5 9 6 6 9 8 9 9 7 72 7 8

6 7 7 5 6 1 7 6 8 0 5 9 8 7 1 6 0 9 2 5 6 6 7 0 6 6 6 2

0 4 9 7 7 8 6 6 9 5 6 9 9

6 9 5 6 0 5 7 7 0 6 6 7 5 6 7 7 6 8 9 6 7 2 4 0 5 8 5 5 6 6 8 9 9 0 7 6 162000 8 68 162000 6 6 6 0 0 5 5 4 6 9 6 7 6 8 7 5 5 5 6 5 6 69 6 8 6 6 1 68 9 7 9 5 6 62 4 8 9 5 8 6 6 6 5 6 6 8 Legend 5 6 0 5 7 9 68 9 9 9 6 0 6 2 4 1 2 7 7 7 6 5 8 6 6 6 6 6 8 8 5 8 2 9 7 8 6 7 5 5 5 67 4 6 6 5 68 5 6 8 5 6 6 6 9 8 6 6 3 5 8 2 0 4 5 5 6 67 6 7 7 9 Contours 7 4 6 66 5 5 5 6 0 0 5 4 7 66 6 4 5 5 59 0 5 7 7 58 5 5 0

8 7 5 5 6 4 6 6 7 8 0 5 6 0 6 3 5 4 2 6 6 1 6 .000000 6 6 6 6 6 .000000 5 5 8 8 9 5 5 4 6 0 5 6 2 4 5 56 6 4 9 5 5 2 6 7 5 5 1 6 8 6 3 5 5 6 65 6 8 7 3 7

5 6 8 6 8 2 5 0 71

5 4 7 159000 159000

498000 .000000 502000 .000000 506000 .000000 510000 .000000 514000 .000000 518000 .000000 Scale: 1:100,000 52.5 0 5 Kilometers Fig. 5 Resulting Contour of the Project Area 29

3.2 DATA PROCESSING AND ANALYSIS DEM The Digital Elevation Model (DEM) created in ArcGIS using the contour features. The DEM is a digital grid in which each cell holds the elevation value of the land space the cell represents.

Fig. 6 Screen Print of DEM of the Project Area 30

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3.3 DEM VALIDATION • The DEM was validated using orthometric heights derived from GPS surveys of random points across the project area. The full details are in the paper proper. But Table 1 shows the statistics Table 1: Statistics of the Validation: GPS orthometric height value minus DEM value Topo Sheet ASTER DEM SRTM of DEM of Study Area Study Area Average -0.372 5.064 -4.124 RMSE 1 1.513 7.555 4.549 RMSE 2 0.731 7.834 4.237

COMPARING WITH OTHER POSSIBLE SOURCES OF DEM SOURCES OF DEM RMSE – Open Areas RMSE – Forest Areas SPOT - flat 2.97m 3.66m terrain SRTM X-band 3.97m 4.49m SRTM C-band 4.25m 6.14m ASTER 7.29m 8.08m Without outlier With 2% outlier of distorted site badly distorted site Updated Topo 0.731m 1.513m Map

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GIS Delineated Drainage Lines of Owerri

498000 .000000 502000 .000000 506000 .000000 510000 .000000 514000 .000000 .000000 .000000 171000 - 171000 .000000 .000000 168000 168000 .000000 .000000 165000 165000 .000000 .000000 162000 162000

Legend

OwDrainageLine .000000 .000000 159000 159000

498000 .000000 502000 .000000 506000 .000000 510000 .000000 514000 .000000 Scale: 1:82,575 31.5 0 3 Kilometers Fig. 13 Owerri Drainage Network. 33

GIS Delineated Drainage Lines and Sub-catchments of Owerri

498000 .000000 502000 .000000 506000 .000000 510000 .000000 514000 .000000

.000000 320.053509 .000000 869.883641 466.236802 171000 171000

1477.021568 1251.659301 - 461.573082 360.276453 .000000 .000000 Legend

168000 OwDrainageLine 168000 653.824198 744.66283 725.350858 Subcatchments Area 713.981928 886.316975 320.05350896 360.276453488 461.573081563 .000000 495.736436 .000000 652.461431 466.236801963 487.301701449 165000 165000 495.270605097 631.902404 495.736435724 615.032625947 628.232693178 631.90240374 652.461431266

.000000 653.824198211 .000000 683.164517 1942.420285 487.301701 1157.544648 683.164517103 713.981928217 162000 162000 628.232693 1158.68691 725.350858253 744.662830032 869.883640897 886.316975499 1157.54464801 615.032626 495.270605 1158.68691022 .000000 .000000 1251.65930107 1477.02156835

159000 1942.42028488 159000

498000 .000000 502000 .000000 506000 .000000 510000 .000000 514000 .000000 Scale: 1:82,575 31.5 0 3 Kilometers Fig. 14 Drainage Map of Owerri 34

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GIS EXTRACTED SUB -CATCHMENT DETAILS FOR COMPUTING DRAINAGE SIZES Table II Characterized Sub-catchments of the Project Area Sub- Area Remotest Overland Width catchment (Ha) Y_Centroid X_Centroid Flow Distance, L (m) Slope (%) (m) S1 1157.54 161700.48 500830.80 1432.11 0.486 8082.77 S2 320.05 171227.33 514032.48 722.51 2.366 4429.68 S3 615.03 159539.54 502904.44 2522.83 0.396 2437.86 S4 456.57 170762.16 508281.35 1085.99 1.03 4204.19 S5 495.74 165118.87 505752.40 1140.55 0.069 4346.50 S6 886.32 166016.09 509332.90 2149.93 2.315 4122.56 S7 1477.02 170084.91 511135.03 1469.61 0.748 10050.43 S8 354.97 168725.92 513545.97 2135.11 0.234 1662.54 S9 744.66 167223.58 513030.31 1192.08 1.786 6246.73 S10 869.88 170901.82 505192.39 2618.87 1.743 3321.58 S11 653.82 167330.77 507795.25 2450.65 1.743 2667.94 S12 461.57 169178.96 507050.22 2771.70 2.374 1665.30 S13 1158.69 160768.00 511673.93 2009.05 0.163 5767.36 S14 631.90 163851.51 509725.27 1332.84 1.808 4741.01 S15 1251.66 169670.38 502672.01 1494.89 0.331 83507.46 S16 683.16 162022.01 502794.91 966.39 0.425 7069.17 S17 725.35 167044.46 504362.61 1297.33 0.679 5591.08 S18 487.3 161855.52 499520.62 2063.47 0.606 2361.56 S19 495.27 159135.15 508560.42 844.39 0.012 5865.40 S20 713.98 165955.20 502086.13 1836.94 0.543 3886.79 S21 1942.42 161975.48 505499.64 2040.57 0.213 9518.99 35 S22 652.46 164832.79 512204.07 2404.46 1.262 2713.54

OVERLAY OF THE GIS DELINEATED PRIMARY DRAINAGE ROUTES OF OWERRI WITH THE EXISTING ROAD EDGE DRAINAGES

Fig. 15 Map of the Project area showing the natural flow routes, roadside drainages, streams and rivers. 36

FIG Working Week 2015 18 26-05-2015

3.2.5 Results and Discussion • From Fig. 15, it is seen that the road edge drainages do not match the delineated primary drainage routes of Owerri. • Efficient drainage systems will mitigate urban flooding. • Efficiency of drainages depend on the location of the drainages, the alignment of the drainages, the slope of the drainages, the sizes of the drainages and the sizes and numbers of inlets of the drainages.

3.2.5 Results and Discussion Contd. • The natural flow routes of the sub-catchments should form the primary drainage routes of each sub-catchment in the urban area. In most cases the artificially designed blocks of urban land use, often bordered by roads, should form the secondary routes that are channeled to empty into the primary drainages. The plots that make up the blocks are drained in the tertiary drainage scheme into the secondary drainage systems. • The most critical urban drainages to mitigate flooding are the primary drainages. If they are not properly in place every other drainage may serve at best as blocked conduits and will not serve to mitigate flooding in the area.

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3.2.5 Results and Discussion Contd.

• The greater part of the drainages of the study area were constructed alongside the road edges. The map of the delineated natural flow routes was overlaid on the map of the study area to create Fig. 15. It presents the main express routes with some sizeable drainages shown in black lines while the delineated sub- catchment natural flow routes are shown in red.

SITE CHECK FOR EFFICIENCY FACTOR

• The first set of drainage efficiency factors to consider are the location factors, the position of the drainages and the horizontal alignment. • The second set of drainage efficiency factors are the flow factors, the size and vertical alignment depend on the first efficiency factors. They only need to be checked if the first factors are in place. • The third drainage efficiency factors, the runoff capture factors or the inlet factors (number, size and location of inlets) are the fourth and are necessary to check if the second set are in place.

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3.2.6 SITE VALIDATION OF DRAINAGE AREAS On 6th October 2011 and 20 th July 2012 visits were taken to 3 of the sites delineated in the analyses to be drainage lines to check their state of flooding or otherwise after the rains. It was discovered that they were heavily flooded. The photographs presented hereunder are those of the visited sites.

• .

Works Layout Area 6 th October 2011 : Conduit C11 series. Fully developed pond now due to high runoff coefficient of a developed urban area.

Plate 1 42

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Works Layout Area 6th October 2011 : Conduit C11 series.

Plate 2 43

Works Layout Area, 6 th October 2011: Conduit C11 series.

Plate 3 44

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Federal Housing Estate 20 th July 2012: C14 series

Plate 4 45

Federal Housing Estate: 20 th July 2012 C14 series

Plate 5 46

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Federal Housing Estate: 20 th July 2012 C14 series

Plate 6 47

Federal Housing Estate: 20 th July 2012 C14 series

Plate 7 48

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Chukwuma Nwoha Road Area 20 July, 2012: C14 series

Plate 8 49

4.0 CONCLUSION AND RECOMMENDATION

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4.1 CONCLUSION • CONCLUSION • This paper has demonstrated the determining of the drainage efficiency factors of location, alignment, slope and size using Geographic Information Systems. • The determination of these factors relied completely on the use of Digital Elevation Model (DEM) of the area analyzed on a GIS platform. The DEM was derived from the digitization of the topographic maps of the study area on a GIS platform. The DEM was validated using GNSS observations. • The paper has shown that drainages constructed for Owerri have not met the drainage efficiency factors. • The paper concludes that it is the failure of the drainages of Owerri to meet the efficiency factors that make Owerri to flood when it rains.

4.2 RECOMMENDATIONS

• In view of the forgoing the following recommendations are made: • Urban flooding will be mitigated if urban areas are provided with efficient drainages. Drainage designs should adopt the GIS approach to be able to accurately determine the efficiency factors. • The need to constantly revise the topographic maps of urban areas every 5 years and undeveloped areas every 10 years cannot be over emphasized. Government is encouraged to carry out these revisions to provide accurate and up to date data for the revising of drainage efficiency factors. • Governments should ensure that the determined natural flow routes are marked on the ground both in urban and rural areas and even farmlands. Legislations should be enacted and people educated to stay off those routes for the inherent dangers of flooding the areas due to the routes being blocked by blockages erected along these drainage routes. • Since natural drainage routes are actually routes eroded over time by runoff, the Geographic Information System Based Approach to mapping of natural drainage routes will lend itself to erosion studies of the area.

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THANK YOU

References • REFERENCES • • [1] Ginkel, H. V. (2008) Terms, Images and Realities: The future of Urbanization. United Nations University. www.merit.unu.edu/archive/docs/.../200905_20090414_vanginkel.pdf • [2] ActionAid International (2006) Climate Change, Urban Flooding and the Rights of the Urban Poor in Africa: Key findings from six African cities, ReliefWeb report, International Emergencies and Conflict Team, London, UK, http://reliefweb.int/node/23269 • [3] Abdoulaye D. (2010) Overview of the flood Situation in West Africa in 2010: the role of Spatial Information Management” http://www.un-spider.org/book/export/html/5088 • [4] Etuonovbe, A. (2011) The devastating effect of flooding in Nigeria. Paper presented at the FIG Working Week. Marrakech, Morocco, 18th-22nd May. • [5] D. Ram Mohan Rao. M. R. D., Ahmed, Z., Reddy, M. R. K., Raj, E. (2013) Selection of Drainage Network Using Raster GIS – A Case Study, International Journal of Engineering Science Invention Vol. 2(8), 2013. PP.35-40 http://www.ijesi.org/papers/Vol%202(8)/Version- 1/F0281035040.pdf Accessed January 31 , 2015. • [6] Al-Saud M. (undated) Use of Remote Sensing and GIS to Analyze Drainage System in Flood Occurrence, Jeddah - Western Saudi Coast, Space Research Institute, King Abdel Aziz City for Science and Technology, Kingdom of Saudi Arabia http://cdn.intechopen.com/pdfs- wm/30392.pdf ) Accessed on January 31, 2015

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References Contd. • [7] Gumbo, B., Munyamba, N., Sithole, G., Savenije H. H. G. (2002), Coupling of digital elevation model and rainfall-runoff model in storm drainage network design, Physics and Chemistry of the Earth, Parts A/B/C (2002), 27: 755-764. www.elsevier.com/locate/pce. • [8] Giron, E. (2005) Development of a SWMM-GIS Flood Model for New Orleans Drainage Pumping Station No 4 Basin, Ph.D. Dissertation, Graduate Faculty, University of New Orleans. • [9] Maidment, D. R.,(Ed.) (2002) Arc Hydro GIS for Water Resources, ESRI Press, California, U.S.A. • [10] Lo, C. P., Yeung, A.K.W. (2002). Concepts and Techniques of Geographic Information Systems Prentice Hall, Inc., New Jersey • [11] Geodetic Surveys Ltd. (1977) Owerri Nucleus Sheet Map series. Government of Imo State, Nigeria • [12] Mark, D.M., 1984. Automated detection of drainage networks from digital elevation models. Cartographica 21, 168–178. • [13] Sefercik, U, Jacobsen, R., Oruk, K., Marangoz, A. “ Comparison of SPOT, SRTM, and ASTER DEMs” http://www.isprs.org/proceedings/XXXVI/1- W51/paper/Sefercik_jac_oruc_maramgoz.pdf [Undated. Accessed July 2012] • [14] Vanguard Newspaper of Nigeria of Monday 27th June 2005 “Flood Sacks 3500 Families in Owerri” www.accessmylibrary.com/.../flood-sacks...

BIBLIOGRAPHICAL NOTES - DR. A. C. CHUKWUOCHA • Dr. Akajiaku Chukwunyere Chukwuocha hails from Itu Ezinihitte Mbaise, Imo State Nigeria. He is a thorough bread Surveyor and a clergyman of the Anglican Diocese of Owerri, Nigeria. He is presently the Administrator and Vicar of the Cathedral Church of the Transfiguration of our Lord, Owerri. Dr. Chukwuocha holds a Ph.D. in Surveying and Geoinformatics from Nnamdi Azikiwe University Awka, Nigeria, M.Sc Geoinformatics and Surveying, University of Nigeria, Nsukka, B.Sc. (Hons.) Surveying and Photogrammetry, Enugu State University of Science and Technology Enugu, and Diploma in Land Surveying from the Federal Polytechnic, Nekede Owerri. • Dr. A. C. Chukwuocha is a member of faculty of the Federal University of Technology, Owerri, Nigeria. His research interests span Global Navigational Satellite Systems (GNSS), Geographic Information Systems (GIS) and Geodesy. He is a Registered Surveyor with the Surveyors Council of Nigeria (SURCON), a full member of the Nigerian Institution of Surveyors (NIS). He is a member of the National Association of Geodesy (NAG) of Nigeria, a member of the National Union of Radio and Planetary Sciences (NURPS).

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BIBLIOGRAPHICAL NOTES - DR. A. C. CHUKWUOCHA contd. • Dr. Chukwuocha has a very wide field of experience in the Surveying Industry. From the time of graduation he has worked with the Owerri Capital Development Authority, Owerri Nigeria with leadership responsibilities in urban development design, monitoring and control. He later worked in the Oil mineral exploration industry in the Niger Delta region of Nigeria with the American Western Geophysical Company, and the French Compagnie General De Geophysique (CGG). Dr. Chukwuocha who played very important roles in the development control of the present Owerri Capital Territory of Imo State Nigeria by spearheading the densification of survey controls across the capital territory from the late 1980s to the mid-1990s still has interest in control densification using electronic methods. • He has published a number of works in Surveying and Geoinformatics including his Ph,D, research on “GIS – Based Approach to Urban Drainage Network Design” (2012), “Delineation and Characterization of Sub-catchments of Owerri, South East Nigeria” – American Journal of Geographic Information System, 2014, 3(1), pp. 1-9; GIS Based Mapping of Natural Drainage Routes of Owerri, South East Nigeria, - International Journal of Current Research, India. (Accepted 2013); “Modern Trends in Topographic Data Collation for Environmental Studies and Engineering, Journal of Environmental Design and Technology, Owerri. Vol. 1 (3). 2012., “GIS – Based Urban Planning and Monitoring Best Practices for West Africa” African Journal of Environmental Science and Technology, vol. 8(1), 2014, among others. • Dr. Chukwuocha also authored the book, “The War Within”, published in 2009 under the Hippo Titles of Zondervan publishers, Grand Rapids, MI, U.S.A. The book which explores the Christians quest to live up to the call to perfection in Christ may still be his most outstanding work. 57

BIBLIOGRAPHICAL NOTES - MRS. NGOZI B. AC- CHUKWUOCHA • • Mrs. Ngozi Blessing AC-Chukwuocha holds a Diploma in Quantity Surveying from the Federal Polytechnic, Nekede Owerri, B.Sc. (Hons.) Estate Management, Enugu State University of Science and Technology Enugu, M.Sc in Environmental Management, Enugu State University of Science and Technology Enugu. She is currently a Ph.D. candidate at the Rivers State University of Science and Technology, Port Harcourt, Nigeria. • Mrs. AC-Chukwuocha is a Registered Environmental Specialist with the National Registry of Environmental Professionals, U.S.A. She is a member of the Nigeria Environmental Society (NES). She has published quite a number of works including, “Trace metal availability in soils of watershed in relation to land use in Owerri, South East Nigeria” Journal of Science and Sustainability (NREP), 2011, “A Comparative Analysis of emission of methane from live stock farms in Enugu, South East Nigeria”, Journal of Agricultural Science and Technology, 2011, “Physio-chemical gradient and in-situ yield in pelagial primary production of the middle reaches of Imo River in Etche, South East Nigeria”, Journal of Ecology and Natural Environment 2011. • Mrs AC-Chukwuocha is a staff of the Department of Environmental Technology of the Federal University of Technology, Owerri, Nigeria. She continues to provide leadership for the women of the Cathedral Church of the Transfiguration of Our Lord, Owerri, Nigeria, where she serves as the Vice President of the Women Ministries of the Church. She is an avid lover of people and keeps working in every way to improve the quality of their lives. • • 58

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CONTACTS

• • Akajiaku C. Chukwuocha • Department of Surveying and Geoinformatics, Federal University of Technology, Owerri, • Owerri • NIGERIA • Tel. +2348033398505 • Email: [email protected] • and • Ngozi B. AC-Chukwuocha • Department of Environmental Technology, Federal University of Technology, Owerri, • Owerri • NIGERIA • Tel. +2348036755194 • Email: [email protected]

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