Defining a Topographic Index Threshold to Delineate Hydrologically Sensitive Areas for Water Resources Planning and Management

Document Type

Article

Publication Date

9-1-2020

Abstract

Hydrologically sensitive areas (HSAs) are runoff-generating areas often targeted for effective water resources planning and management actions. Commonly, HSAs can be mapped as areas in a landscape with a topographic index (TI) greater than a threshold level. This study explored the impact of a gradient of different TI threshold values for delineating HSAs using two popular TIs: a topographic wetness index (TWI) and a soil topographic index (STI). The resultant HSAs for each TI were compared to the Federal Emergency Management Agency (FEMA) 100-year floodplain map in New Jersey and its five water regions. Spatial comparison indicators were used to assess the spatial similarity between the HSAs delineated and the FEMA floodplain map. Such comparisons identified the threshold that delineated HSAs whose spatial distributions were most consistent with the FEMA floodplain at each spatial scale for each TI. For example, the identified threshold for using a TWI to delineate HSAs was 10.5 at the state level; however, this threshold varied by the water region. The HSAs delineated approximate the spatial extent of runoff-contributing areas to the 100-year flood relevant for water resources planning and management actions for flood hazard mitigation.

Identifier

85089088076 (Scopus)

Publication Title

Water Resources Management

External Full Text Location

https://doi.org/10.1007/s11269-020-02643-z

e-ISSN

15731650

ISSN

09204741

First Page

3675

Last Page

3688

Issue

11

Volume

34

Grant

P103201-F103561_NJIT-FY18

Fund Ref

William Penn Foundation

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