Abstract
The study is on flood risk analysis in Mathare, Kamukunji and Makadara Sub-Counties. The objective of this study is to utilize Geographic Information System (GIS)-based hydrological model with remote sensing to analyze the risk of flood in the residential areas of the three sub-counties. Synthetic Aperture Radar (SAR) data was obtained from Sentinel Mission 1 via Copernicus Open Access Hub. Corrected data SAR data was used to create a 10m resolution Digital Elevation Model (DEM). Multispectral Satellite Imagery that was used to perform Land-use/Land-cover analysis using object-based classification method. Ten classes were created. Several factors affecting flood risk were analyzed and among them were LULC and channel flow length, which mainly affected floods in the Area of Study (AOS). The area of study was delineated into four catchments using Arc Hydro Tools. The Hydrological Soil Groups of the AOS were used to sub-divide the catchments into 17 sub-catchments in order to get accurate CN values. Hydrological Engineering Center’s Geospatial Hydrological Model System (HEC-GEOHMS) helped in obtaining channel slope and flow length that were used in calculating the time of concentration for peak discharge and runoff. U.S Soil Conservation Service Technique Release 55 (SCS TR-55) model helped in predicting rainfall-induced flood. Runoff was determined using equations in the model and the peak discharge was computed by the model’s graphical method. The overall map was produced using ArcGIS software by summing up the values obtained from runoff. The results indicated that rainfall-induced flood is a serious problem with flood depth of 13-19.5cm. Decrease in catchment’s flow length and increase in the number of impervious areas due to growth of urbanization increased flood risk in the area. The results of this study will be useful in coming up with solutions for flood risk control which include drainage systems that will improve the infiltration capacity of runoff, appropriate infrastructure e.g., green infrastructure and early warning systems such as sensors on rivers, drainage systems etc.
References
Bayazıt, Y., Koç, C., & Bakış, R. (2021). Urbanization impacts on flash urban floods in Bodrum Province, Turkey. Hydrological Sciences Journal, 66(1), 118-133.
Brilly M, Rusjan S, Vidmar A. 2006. Monitoring the impact of urbanisation on the Glinscica stream. Phys Chem Earth Parts A/B/C. 31:1089–1096.
Burges, S. J. (1986). Trends and directions in hydrology. Water Resources Research, 22(9S), 1S-5S.
Camorani G, Castellarin A, Brath A. 2005. Effects of land-use changes on the hydrologic response of reclamation systems. Phys Chem Earth Parts A/B/C. 30:561–574.
Cheseto, M. N. (2013). Challenges in planning for electricity infrastructure in informal settlements: Case of Kosovo village, Mathare valley–Nairobi (Doctoral dissertation, University of Nairobi).
Dang, A. T. N., & Kumar, L. (2017). Application of remote sensing and GIS-based hydrological modelling for flood risk analysis: a case study of District 8, Ho Chi Minh city, Vietnam. Geomatics, Natural Hazards and Risk, 8(2), 1792-1811.
Dawod GM, Mirza MN, Al-Ghamdi KA. 2011. GIS-based spatial mapping of flash flood hazard in Makkah City, Saudi Arabia. JGIS. 03:225–230.
Fleming M, Doan J. 2009. HEC-GeoHMS geospatial hydrologic modelling extension: user’s manual version 4.2. California: US Army Corps of Engineers, Institute for Water Resources, Hydrologic Engineering Centre.
Gholami V, Mohseni Saravi M, Ahmadi H. 2010. Effects of impervious surfaces and urban development on runoff generation and flood hazard in the Hajighoshan watershed. Caspian J Environ Sci. 8:1–12.
Ho LP. 2008. Impacts of climate changes and urbanisation on urban inundation in Ho Chi Minh City.
Kinyua, G. J., & Fujimi, T. (2018). Risk Analysis of Flood Physical Vulnerability in Residential areas of Mathare Nairobi Kenya.
K. Smith and R. Ward 1998 floods physical processes and human impacts on chi Chester, Volume 24, issue 13
Lempert R, Kalra N, Peyraud S, Mao Z, Tan SB, Cira D, Lotsch A. 2013. Ensuring robust flood risk management in HoChi Minh city. World Bank Policy Res Working Paper. 6465:1–63.
Merwade V, Cook A, Coonrod J. 2008. GIS techniques for creating river terrain models for hydrodynamic modelling and flood inundation mapping. Environ Modelling Softw. 23:1300–1311.
Ramiaramanana, F. N., & Teller, J. (2021). Urbanization and Floods in Sub-Saharan Africa: Spatiotemporal Study and Analysis of Vulnerability Factors.
Sarker MZ, Sivertun A. 2011. GIS and RS combined analysis for flood prediction mapping – a case study of Dhaka City Corporation, Bangladesh. J Electr Control Eng. 1:250–257.
Seeni M. I, Mansor MA. 2000. Application of remote sensing and hydrological modelling in flood prediction studies. Malaysian J Remote Sens GIS. 1:91–98.
Shadeed S, Almasri M. 2010. Application of GIS-based SCS-CN method in West Bank catchments, Palestine. Water Sci Eng. 3:1–13.
Shuster W, Bonta J, Thurston H, Warnemuende E, Smith D. 2005. Impacts of impervious surface on watershed hydrology: a review. Urban Water J. 2:263–275.
Smith, H. M., Wall, G., & Blackstock, K. L. (2013). The role of map-based environmental information in supporting integration between river basin planning and spatial planning. Environmental Science & Policy, 30, 81–89.
Sivertun A, Prange L. 2003. Non-point source critical area analysis in the Gissel€o watershed using GIS. EnvironModelling Softw. 18:887–898.
Soulis K, Valiantzas J. 2011. SCS-CN parameter determination using rainfall-runoff data in heterogeneous watersheds– the two-CN system approach. Hydrol Earth Syst Sci Discuss. 8:8963–9004.
Rafiq, F., Ahmed, S., Ahmad, S., & Khan, A. A. (2016). Urban floods in India. International Journal of Scientific & Engineering Research, 7(1), 721-734.
UN Habitat. The challenge of slums: Global report on human settlements 2018. Manag. Environ. Qual. 2004, 15, 337–338.
UN Habitat. The challenge of slums: Global report on human settlements 2003. Manag. Environ. Qual. 2004, 15, 337–338.
Vitvar, t., Gurtz, j., & Lang, h. (1999). Application of GIS-based distributed hydrological modelling for estimation of water residence times. In Integrated Methods in Catchment Hydrology: Tracer, Remote Sensing and New Hydrometric Techniques: Proceedings of an International Symposium Held During IUGG 99, the XXII General Assembly of the International Union of Geodesy and Geophysics, at Birmingham, UK 18-30 July 1999 (Vol. 22, p. 241).
World Health Organization. Guidelines for Drinking Water Quality, Vol.1, Recommendations, 4th ed.; World Health Organization: Geneva, Switzerland, 2011.
World Health Organization; Health topic/ Floods Article. https://www.who.int/health-topics/floods. Xu, Z., Xu, J., Yin, H., Jin, W., Li, H., & He, Z. (2019). Urban river pollution control in developing countries. Nature Sustainability, 2(3), 158-160.
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