Relative Effect of Location Alternatives on Urban Hydrology. The Case of Greater Port-Harcourt Watershed, Niger Delta

Abstract

Globally, cities in developing countries are urbanising at alarming rates, and a major concern to hydrologists and planners are the options that affect the hydrologic functioning of watersheds. Environmental impact assessment (EIA) has been recognised as a key sustainable development tool for mitigating the adverse impacts of planned developments, however, research has shown that planned developments can affect people and the environment significantly due to urban flooding that arises from increased paved surfaces. Flooding is a major sustainable development issue, which often result from increased paved surfaces and decreased interception losses due to urbanisation and deforestation respectively. To date, several environmental assessment studies have advanced the concept of alternatives, yet, only a small number of hydrologic studies have discussed how the location of paved surface could influence catchment runoff. Specifically, research exploring the effects of location alternative in EIAs on urban hydrology is very rare. The Greater Port-Harcourt City (GPH) development established to meet the growth needs in Port-Harcourt city (in the Niger Delta) is a compelling example. The aim of this research is to examine the relative effect of EIA alternatives in three different locations on urban hydrology. The Hydrologic Engineering Centre’s hydrologic modelling system (HEC-HMS) hydrodynamic model was used to generate data for comparing runoff in three different basins. HEC-HMS software combine models that estimate: Loss, transformation, base flow and channel routing. Results reveal that developments with the same spatial extent had different effects on the hydrology of the basins and sub-basins in the area. Findings in this study suggest that basin size rather than location of the paved surface was the main factor influencing the hydrology of the watershed.

Watersheds and stream networks viewed longitudinally: Example insights from novel spatial portrayals of watershed characteristics

“…Many studies have found that development location can significantly alter the magnitude of peak streamflows (Du, Shi, van Rompaey, & Wen, 2015; Yang, Bowling, Cherkauer, & Pijanowski, 2011; Yeo & Guldmann, 2006). Basin size, impervious surface connectivity, and flow timing have been found to have significant impacts on peak flow as well, which may explain the differing conclusions about which basin position is best for development (Dan‐Jumbo & Metzger, 2019; Du et al, 2015; Mejía & Moglen, 2010).…”

Geographic Location System for Identifying Urban Road Sections Sensitive to Runoff Accumulation

“…Synthetic hydrographs provide an empiric representation of the response of small catchments to short and uniform rainfall events. Among them, the SCS hydrograph is one of the most widely used and cited models in specialised literature related to surface hydrology [36]. It is triangular and provides the basic hydrological parameters of a hydrograph.…”