Development and Evaluation of Flood Mitigation Strategies for Greens Bayou in Houston - Resilience Vs. Resistance Approach

Houston, TX is a severely flood-prone area, and Greens Bayou is one of its frequently flooded watersheds. Even though parts of the watershed have been inundated multiple times, it has benefited from very few flood reduction projects. Large population near or below poverty line, multi-family housing areas, and homes built in the 10 year floodplain are the distinctive characteristics of this repeatedly flooded watershed. In light of these facts, this study compares the effectiveness of two contrasting flood mitigation approaches within the Greens Bayou watershed: "Living with Floods" (integrated mitigation approach that uses land management techniques and structural measures), and "Flood Defense" (mainly focused on engineered stormwater controls). The former approach employs green infrastructure (GI) practices such as green roofs, permeable pavements, bioswales, underground storage and infiltration system, regional stormwater ponds, and constructed wetlands. The goal of this study is twofold. First, to identify challenges in capturing GI information in hydrologic and hydraulic (H&H) models (HMS and RAS). Second, to analyze floodplains modeled in RAS under both the mitigation scenarios and to evaluate the extent to which natural flood mitigation can be utilized in a region prone to extreme high-intensity precipitation events. This study is divided in three phases: (1) Creation of inundation maps using 1D unsteady RAS simulations developed for major weather events occurring in Houston since year 2001 to understand the flooding trend in the region and identify repetitive flood loss locations. (2) Development of 1D, 1D/2D coupled and 2D unsteady RAS models to generate 100 year and 500 year floodplains. These maps are utilized in phase 3 to study effectiveness of the flood mitigation plans. (3) Incorporation of flood mitigation options in RAS models, and generation of 100 year and 500 year floodplains for comparison with baseline year 2017 maps. 1D/2D and 2D models created in phases 2 and 3 aid in modeling levee or detention ponds more precisely. This study helps in understanding how H&H models can be used effectively to explore suitability of GI/land management option to the watershed.