Sea level variations and the impacts along the coastal areas of Nigeria

A brief review of the Nigerian Coastal Areas including the geology, geomorphology, topography, climate, and vegetation has been given. Nigeria has a coastline of about 850km facing the Atlantic Ocean and the coastal areas support a population of about 20 million people and a myriad of economic activities. Global sea level is known to be rising gradually and in some areas due to subsidence either from natural tectonic actions or in combination with fluid withdrawal from under the ground, the rate is much higher than the global average. The latter situation is believed to be the caseon the Nigerian Coast where oil and gas exploitation and water supplies are being withdrawn from under the ground at uncontrolled rates. Tidal data obtained from the Nigerian Coast have been used to study the various sea level variations on that Coast.Using 19 years of tidal data from Bonny, the sea level is observed to be rising at the rate of about 1mm per annum compared to the global average results between 1 -2mm per annum. Forty years of tidal data from Takoradi Port, Ghana also on the Atlantic Coast of West Africa have showed a rise of 3.9mm per annum. The contribution due to subsidence has not been determined because the tide gauge benchmark have not been connected to a stable control point and monitored regularly. Maximum surges of the order of 7m were observed. Other variations and characteristics of the sea level on the Nigerian Coast include seasonal, tidal ranges, frequency distribution of tidal data, and behaviour of the tidal data in absence of some major tidal constituents. The impacts of these variations on the Nigerian Coast have been studied. These include erosion, flooding and inundation, salinity intrusion, destruction of coastal settlements, deforestation and destruction of the marine ecosystem, increased effect of oil spillage on the Coastal environment, and destruction of infrastructural facilities and industries. Response measures have been discussed and the integrated management of the coastal areas of Nigeriais seen as a very important response in addressing the impacts, development, and management of the Nigerian Coastal environment. Continuous data collection, monitoring of the various processes on the Coast, further researches and regional cooperation on the issue of sea level variations are recommended as very important component

Dredging of the inland waters and sustainable management of the waterways for national development

Inland waterways transportation is a key component of the intermodal transportation network and is essential to Nigeria’s economy, environment and quality of life. IWT has a significant part to play in the states of Niger, Kogi, Anambra, Delta, Bayelsa, Rivers, Akwa-Ibom, Benue, Adamawa, Cross River and Lagos. The waterways in these states connect several minor ports/jettys and the major port of Baro, Lokoja, Onitsha, Warri and Apapa as well as the host of industries located along the river. Inland waterways have remained the most neglected segment of Nigerian transportation system. Though inland water transport (IWT) is comparatively a cheaper and efficient means of transportation, in the nearest future, the utilisation of this mode of transport shall be enhanced by the successful completion of the on-going dredging of the river Niger. Anticipated derivable benefits from the dredging of the Niger Water system would among others, include: ocean remediation, upland restoration, improved transportation system, economic viability, increase volume of cargo, improved communication, Job opportunities, decongestion of sea/coastal ports, and improved lifespan of roads, filling degraded basins and pits, creating and restoring wetlands for water quality treatment and habitat and creation/restoration of other habitats, such as, oysterreefs and bird habitat.Key words: Inland Waterways Transportation, Dredging, River Niger, Mode of Trave

Transformation of Shuttle Radar Topography Mission (SRTM) Digital Elevation Data to Nigerian Height System

Determination of height information using the classical field surveying and geodetic methods is rather expensive, rigorous and time consuming. It is also limited in the capacity of the earth surface data gathered. These conventional topographic mapping technologies have produced maps with a variety of scales and of uneven quality - some with astounding accuracy, some far less adequate. A good alternative is the Shuttle Radar Topography Mission (SRTM) derived Digital Elevation Model (DEM) which provides an excellent base data for extracting heights for topographic mapping. This will ameliorate the present situation. The SRTM space mission produced the most complete, highest resolution digital elevation model of the Earth. This study is aimed at developing a model for the transformation of the SRTM heights from WGS84 datum to the Nigerian height system (Minna datum) using SRTM derived DEM, topographic map and Global Positioning System (GPS) data of some parts of Lagos state, Nigeria. The chosen site corresponds to the area covered by one map sheet at the scale of 1:25,000 (13.8km x 13.8km) which is 190.44sq.km. Software such as Globalmapper, Surfer 8.0 and ArcGIS 9.3 were used for specialized data processing and analysis. However, the datasets obtainedwere first projected to a common system and subsequently harmonized. This was carried out with an overlay of GPS points on the grid based SRTM and topographic DEM surfaces of the environment. Results showed deviation in heights with coinciding planimetry data. The average absolute error of the SRTM DEM for our test site was gotten as +/-0.22087m. Finally, by modelling this vertical shift, a transformation model that is accurate with a standard error of 0.238m was developed

Determination of Land Surface Temperature (LST) and Potential Urban Heat Island Effect in Parts of Lagos State using Satellite Imageries

Temperature is an important component of the climate. The temperature of a developing city or state is constantly changing. The trend in temperature change in Nigeria is not consistent. Changes in temperature appear to be closely related to concentrations of atmospheric carbon dioxide. The degree of concentration depends on human interventions and the amount of sunlight reaching the earth's surface. Lagos State particularly in recent time has experienced decrease in vegetation and water pervious surfaces, which reduces surface temperature through evapotranspiration. This is as a result of rapid urbanization arising from inundating rural-urban migration. One of the implications is that anthropogenic heat is released to the environment due to energy consumption and increased impervious surface coverage thereby increasing the surface and atmospheric temperatures. LandSat Satellite imageries have been used to estimate Land Surface Temperature (LST) and urban thermal conditions. The mean LST result shows that, there is a significant increase in the temperature values from 1984 to 2002 (28.40oC-28.86oC). However, in 2006 the temperature decreases significantly to 28.37oC below 2002 temperatures in all LGAs. This variation could be attributed to the economic crisis/power outage in Nigeria which left manufacturing companies out of production/manufacturing between 2002 and 2006. Findings from this study reveals that there is a relationship between the surface temperature and the various Land Cover types. It shows a broad classification of the Land Cover types into Water bodies, Vegetation and Built-up areas respectively. With the spatial resolution and temporal coverage of two Landsat data of the environment, the derivation of the temperature information was achieved