GENERALIZED METHOD FOR ESTIMATING VARIABILITY IN DIRECTLY CONNECTED IMPERVIOUS AREAS
Journal Title:Global Journal of Engineering Science and Research Management (GJESRM)
Determining impervious areas is a key factor regarding the expected amount of runoff in an urbanized watershed.
Imperviousness occurs from land alterations that change the predevelopment hydrology, especially as relates to land cover and its
effects on surface infiltration. An urbanized watershed can be divided into three general types: Directly Connected Impervious Area
(DCIA), Non-Directly Connected Impervious Area (NDCIA), and Pervious Area (PA). Runoff from DCIAs is conveyed directly to
storm water sewers while runoff from NDCIA may pass through a PA before it reaches the drainage system. The amount of DCIA
is highly unknown, yet it is often the dominant factor in most urban environments. Total Impervious Area (TIA) is defined as the
sum of DCIA and NDCIA.
In the past, several methods have been applied in the estimation of TIA. Among these methods are direct field
measurements, empirical equations, and interpretation of satellite images. While empirical relationships have been developed for
different land cover, generalized methods still need to be developed. In this study, DCIA as a function of rainfall depth was
estimated. DCIA reaches its maximum value when enough rainfall has occurred to connect runoff from all impervious surfaces
(TIA). The new approach was tested with rainfall runoff data on a small, but highly urbanized catchment in Temple Terrace, FL.
The result of this research indicated that impervious surfaces become increasingly effective in generating storm water runoff with
increased rainfall depth and decreased infiltration. The results of this research can be used to study the impact of urbanization on
storm water runoff and improve hydrologic modeling